Hand Crafted Tube Preamps & Amps

Richard's Customs & Tube Audio Kits

ShermanAudio

DIY Tube Amps & Preamps

These are my best chronological project start dates

some projects were finished years later...

I faced issues, delays, many needed upgrades & modifications

So my audio signal path targets;

#1 Improvements in audio fidelity

#2 Extending tube life @ 125 VAC mains

#3 Lower static noise floor, for improved *D.D.R.

(*DDR = Downward Dynamic Range)

https://www.audioasylum.com/messages/vinyl/686087/downward-dynamic-range-a-fuller-description

1996 - Lynchburg, VA

Mullard 5-20 Push Pull Monoblocks - Hammond PT/OPT

EL34, ECC83, EF86 & GZ34

20 Watts per Monoblock

A standard that very few have ever heard.

Mullard never produced COTS Amplifiers

They only made some of the greatest Valves.

1998 - San Juan, PR

Kismet-1 Single Ended Stereo - Audio Note 2.6K OPT

2A3, 6N1P & GZ34

3 Watts per channel

If you have never experienced a SE amplifier

You have not ever heard true Class A

Other maybe than Nelson Pass amplifier

1999 - San Juan, PR (redux 2024)

Bros Amp - Experimental Project (still unfinished business)

Power Tubes TBD, Phase Splitter (TBD), Driver (TBD)

XX Watts per channel (TBD)

Plan to revive project into something different

Maybe 7591/7868 or 6L6/5881

2002 - San Juan, PR

Olson Amplifier (SR91 Aurora) - Hammond PT/OPT

6F6S, 6SN7, 6J5, & 5Y3

10 Watts per channel

Built out of curiosity of what a Push-Pull NFB design

really sounded like, It was a revelation in low power

dynamics and clarity.

2003 - San Juan, PR

Dynaco MK3 Clones - Triode Electronics PT/OPT

6550, 12AU7 & GZ37

55 Watts per Monoblock

Adjustable Bias, built in metering

Better layout, cooler running.

Very good project monoblocks

Great PC Boards are available.

Good for Tube Rolling and replacing

the 6AN8 as the Input/Phase splitter.

2005 - San Juan, PR

Kismet-2 Single Ended Stereo - James 2.5K

2A3, 6N1P & GZ34

3 Watts per channel

Gifted to my best friend

clone of the Kismet-1

Current status unknown

Do have parts on hand for a Kismet 3

 

2007 - San Juan, PR

RCA Tube Manual RIAA into Rozenblit SRPP

with separate AC/DC Power Supply

I misplaced the operational photos of the unit, but here is the carcass of the Preamp

Current plan to re-build into just a stand alone RCA/RIAA Phono Stage.

A Dynaco PAS3 Power Transformer, may work quite well with DC on the 12AX7's filaments

Part of my experimental learning curve, built using mostly a Radio Shack Power Supply.

Hence called "The Shacker"

It worked OK, but the Power Supply was never really healthy.

2008 - San Juan, PR

Glassware AIKIDO Preamplifier & Power Supply - Triad PT

6SN7 & 5Y3

Six RCA Inputs, separate power supply,Dual-Choke

Line stage that supports selectable RCA sources.

Position #1 has adjustable input level, for flexibility.

Now have Vcap's TFTP 0.33uF and they are very good Caps

Neutral, Convenient, Upgradable

Lots of interesting upgrades possible.

I want another Motorized Volume Control

The original died......

2009 - San Juan, PR

Transcendent Sound RIAA Phono Stage Kit

6C45P & 12AX7

Modified with 100K Audio Output Level Controls

Otherwise stock kit.

55dB of Gain, makes Vinyl come alive.

Works well with medium output Moving Coils 47K Load

Very low noise input RIAA stage.

tough 12AX7 outputs

2011 - Lynchburg, VA

Dynaco ST-25 special version (SA-35)

 EL-84/6BQ5, 12DW7 & 5AR4

Upgraded with 5AR4 Tube Rectifier

Hammond Power Transformer upgrade

Superior layout, much better sonics

Smoother musicality, my favorite Jazz/Vocal Amplifier

second to the Kismet SE

2019 - Lynchburg, VA

Neo-Classic 30 Guitar Amplifier Head

 6F6S, 6SN7, 6J5, 12AX7 & 5Y3

Musical Instrument Tube Amplifier

Currently owned and in use by a Sterling VA Guitarist

Based on Olson Amplifier with Preamp Stage

Good Amps for close mic studio recording

2022 - Rochester, NY

CAT-1 Preamplifier - KIT

12AU7, 12AX7 & 6922

Currently under construction since December 2022

Ordered new boards from Analog Metric

Unfortunate PSU Board short circuit setback, awaiting parts

Very slow progress. Fixed PSU Board

but does not adjust regulation, still working the problems

PC Boards can be a time saving blessing or a repair curse.

2024 - Rochester, NY

Transcendent Sound "a-semi-KIT"

Cathode Follower Stereo SE Amplifier

(Image above courtesy of Transcendent Sound)

Transcendent Sound

ShermanAudio DIY

Cathode Follower work in progress...

2x 12AX7, 2x 12BH7, & 2x 6550

Currently under construction since March 2024, making steady progress

Chassis, and final metalwork in process, this week I will punch the three Capacitor holes.

Coming in early 2025 - Rochester, NY

Kismet-3 2A3 Stereo Tube Amplifier

No photo, under construction

Currently under planning, based on Fabio Camorani's

fixed Bias Kismet using same chassis as Kismet 2

James 2.5K Output Transformers

Power Supply under re-design for fixed bias.

Might need different PT

Restoration planned for 2025 - Rochester, NY

Stromberg Carlson 1940's Mixing Preamplifiers

Have the parts, need the time to do the restoration/upgrades

Vacuum Tube Mixing Preamplifiers

Plan to build nice wood cases with ventilation panels

Worn Potentiometers need replacement.

Old fashioned Balanced receptacles may need

an XLR swap-out, or I can fabricate cable converters

to leave the Mixers 100% original.

I prefer to fabricate adapters... You know Me.

I dislike to modify classic gear, I prefer pure restoration.

Currently on the workbench in 2024

CAT-1 Preamplifier Kit

This used to be sold on EBay by Analog Metric, I don't see them anymore on EBay, they are direct on their website. I can now see that similar EBay Sellers that have Boards only use Analog Metric as a benchmark. I opted for the CAT-1 Preamp, as my friend owned one, and we enjoyed that Preamp on several "very musical" sessions. The original CAT-1 was built like a Tank, and sported an External Power Supply. It had an obscene amount of Gain, great for Single Ended amps that need a good kick to get them singing the Blues.

Active project Dec 22 - This is a started on December 2022 build, I am pulling out all of the parts and will get this one working by December 31st if all goes to plan. If you want to check out the latest Analog Metric products, just follow the link below. I can really vouch for their quality, The CAT-1 Chassis below is first-class, the Front Panel looks like those $5600 dollar preamps you browse on Audiogon. Once I complete the build, I will use it for a few month's and work out any issues. This CAT-1 package has the heft of products on the upper class, this is a Steel Chassis, not a Featherweight. Note that these Kits are not 100% ready, they require some Drilling as well as some interpretation of the assembly manuals. What they have in product quality is better than their technical writing skills. The graphics are what saves the day, as the instructions are usually covering multiple modular kits and one has to dig for exactly what is needed. The best way is to work backwards, start at the PC Boards and then the requirements will define what needs to happen around the PC boards. You can purchase this Kit with all the bells and whistles..... I will report back when I have it playing. This one is elegant, and is also available in Champagne Color.

http://www.analogmetric.com/

12/16/22 Construction begins....

So finally I got down to my shop early today (I am on an every other Friday off schedule) and happy to show progress.

I drilled out the holes I marked back in 2020/21 but the project actually began way back in 2016.

Another one of my "Victims of TIME", not Judas Priest "Victim of changes".

And this Time, I got into kicking this one off just prior to my Xmas Stay-cation.

The Blue painters tape, it still had the sharpie marks from 2020.

So I selected the proper drill bit and carefully drilled out each hole.

You can appreciate the Toroid Power Transformer - (260V Plate, Regulators for 12V DC and 6DJ8 AC Filament)

I had on hand a Hammond 15H-100ma Choke (leftover from the Aurora 6F6G Stereo Amp).

Power Supply PC Board (Un-populated)

CAT-1 Clone Preamplifier Board (Un-populated)

Guess what?

No Blood today, no cuts, this was a first for me not to injure my fingers.

If you want Blood? You don't got it!!!

I always preach safety, and this time I was extra careful to do everything slowly and deliberately well.

DRILLING PREPARATION

Then mount the main boards and Toroidal Transformer into the chassis.

Slow and methodical, measure twice, drill once.

The next step will be to drill out the chassis, mount the plain PC boards for fit.

Then drill out the remainder of the parts onto the chassis and check for form/function.

Then once the boards and power switch wiring is done,populate the PC Boards.

Then I plan to wire up the Transformer Primary, Fuse, SPST Switch and LED.

Then install the Power Supply Board and Test the HV and DC Filament Voltages.

I always as a rule of thumb first get the Power Supply connected and tested before any Audio Signal electronics.

After all the Power Supply is the Engine Room of any appliance.

The Input and Output RCA's are the artisanal part of this build, as I did not buy the Input Switching PC Board

as I prefer all wiring to be physical, not through relays. This is later in the build

as wire routing depends on where things end up inside, step by step.

All I can say is that the next up on the list, is the Transcendent Cathode Follower Kit.

Once I have this Preamp sounding, the Cathode Follower follows....

Note that I deliberately left Real Estate open for an eventual Phono Preamp upgrade.

I plan to make the Phono Preamp a JFET as Tubes are too noisy for Phono Preamp DIY, unless

of course, you were lucky enough to have built the awesome Transcendent Sound Phono Stage

(I rave about this Phono Stage just look for the photos of what I did with it.)

But for now I am happy with 4x Input Sources and the CAT-1 Clone Build

Progress.... 12/18/22

Progress on my Kit preparation. I managed to re-orient the Toroid, identify the Secondary Wires that are relevant and wire-up

the front panel LED with a 1 MEG Carbon Comp resistor. Out or curiosity I actually measured the Diode Current when connected to

120VAC through a 1Meg Resistor = 5 Milliamps.

So below are the photos of my progress.

One note, I learned from prior builds to tighten the RCA's and orient them so that I can solder the center post from above.

It takes some twisting around to get the Ground Tab to line up.

Next steps, stuff both PC boards with the components

The wiring of the 4 Position Input Selector Switch is the artisanal part as I did not buy the Input Selector PC Board.

Progress is awesome, and the therapy of working on my feet for a few hours is just what I love.

I have a Varidesk so that also helps me stay standing and in shape.

The T30L Toroid HV Wires turned out to be - Brown (230VAC) and (Black 0V).

The 6.3 Volts AC for the 6DJ8/6922 are (Red-Black).

 White Wires are the AC to DC regulator input to produce 12.6 Volts DC for 12AX7 and 12AU7 Filaments

Why the designer did not just create an additional regulator to make 6.3 VDC for all tubes is something we will never know.

I do have a Velleman PSU with 1 Amp, tempted to use that, nahhh, too much OCD-DC.

Maybe the 12AX and 12AU tubes are naturals for a 12.6 Volts DC supply.

Maybe the CAT-1 used 6.3 VAC on the 6DJ8/6922 for a more dynamic sound.

Most people love DC on small signal tubes as it keeps the noise down....

But I love AC on Filaments, it is the basic way to light them up, and saves the complexity

of a DC Supply and will not polarize the filaments over time.

THE POWER SWITCH & LED ARE WORKING!

T30l Toroid Power Transformer Label

This is a universal Toroid with lots of wires and most of them are tucked away....

Next step, input jacks-selector switch and PSU Board, stay tuned!!

1/8/23

Gosh what a Cold I have.

On 12/31/22 I started to feel that I was coming down with something respiratory.

My nose had been leaking for days since Wed Dec 28th.

Body aches and a temperature of 99.8 deg F.

I made it past New Years, as my chest started to feel on fire and my throat hurt.

I was sneezing all day on 12/31/22.

Then it came on like a slow train wreck, I was feeling very tired and my temp was at 100 deg F. on 1/1/23.

I took two home COVID tests and both were negative.

So inevitably my Preamp Project is stuck.

As I write this today I am recovering from a week in Bed and trying to do some work from my Home Office.

Even today I am walking around on my 3rd box of Kleenex, my MUCINEX and CORICIDIN HBP plus my Robitussin DM.

Today I feel better, but still have a runny nose and not yet 100%.

Once I feel better I will complete the Power Supply PC Board and also the Input RCA Jack to Selector switch wiring that is all artisanal stuff.

HAPPY 2023.... I still feel sick as a Dog.

7/30/23

So here I am after 6 month's of dealing with issues at my Job, I managed to complete the Power Supply PC Board.

It came out OK. The Analog Metric manuals and information is not well created.

None of the Schematics matched the PC Board.

But what saved me was the Parts List was 95% close to the product I had purchased.

The bummer was that I discovered this later in the day and I had to de-solder the worst part, a 5K Potentiometer

with very small leads. The PC board suffered, but I hope I managed to fix the issue.

Below are the Photos I took after I finished putting all of the parts together.

The Kit had missing parts, extra parts and incorrect information.

Only due to my experience building stuff I managed to figure out what was going on,

Needless to mention I measured every single part to make sure I did not get a faulty component.

LATER IN THE EVENING I BEGAN TO ASSEMBLE THE CAT-1 PC BOARD

8/25/23

I enjoy my 9/80 Schedule as I get every other Friday OFF!!

Today I woke up already heading down to my Shop to work on the CAT-1 Preamplifier PC Board.

So after I was almost done the Kit was again missing parts.

The Kit was supposed to have 100K, 1Watt Resistors and they were 0.5 Watts.

The Kit was supposed to have 20K, 2Watt Resistors and they were missing.

The Kit was supposed to have 100 Ohm, 1/4 Watt Resistors and they were missing as well.

So I installed everything that I could, including a pair of real Carbon 100Ohm, 1/2 Watts in place of the 1/4Watts.

Below are two pics, one of them was work on progress, the second pic is when I stopped.

Nice Board indeed, but I have ordered again, everyone deserves a chance.

ANALOG METRIC.... good quality, nice kits, sometimes missing or incorrect parts, but I have great parts stock.

This was not my first issue, when I purchased the CAT-1 Black Metal Chassis

one of the RCA Connectors was cross threaded, but they sent me a replacement fast, cool thing.

I don't see them on EBay so customers must have grown weary of the issues.

Now I just order direct, but they build each order one at a time now so be prepared for delays, be patient.

That's all for today. I will start the RCA to Selector Switch artisanal wiring soon, maybe this weekend?

WHO KNOWS WHAT THE FUTURE WILL BRING.

8/30/23

The 20K, 2W and 100K, 1W arrived last weekend.

I installed them and the CAT-1 PC Board is completed.

This weekend I am going to a Duran Duran Concert, so I imagine that

this CAT-1 Preamp project will have to wait a bit....

3/11/24

I have been procrastinating due to personal health issues. I was not well since Thanksgiving.

But I just took my last Antibiotic last night, and feel much, much better. So I decided just 1 hour ago to go for it.

Connect up the Power Supply board, and then dive direct into the Preamp.

I am glad it worked out.

The regulated DC was down at 140VDC so I turned the Pot and brought it up to 260VDC.

The 12.6 VDC was way up at 19 VDC so that needed to drop down to 12.5 VDC.

Happy to report no smoke, and all Voltages Present, even the 6.3 VAC for the 6922.

The pictures below show the Preamp and Power Supply boards all connected to be ready for the

input selector switch, volume control and RCA jack wiring.

This Preamp promises to be a cool sounding appliance.

With the CAT "clone" heritage, it will have plenty of Gain

for my Vintage Sources like the Cassettes and Reel to Reels I so enjoy.

NEXT WEEKEND .... and the next, and the next...

I will pre-wire the selector switch outside of the Preamp.

Pre-wire the Volume Control as well.

Then wire-up the Single Point DC Ground Scheme

Once that is done, the rest is final asembly and bench testing (I hope).

4/5/24

Next weekend.. right!

At my career stage, I don't know where I will be in what city and with what challenge.

So I did manage today, Friday, to make more progress on the CAT Clone.

This is my Friday off and I took my Subaru in for Oil and a regular checkup.

I managed to wire up the Inputs to the 4 way selector switch from notes I made last year.

I always make a drawing before wiring so that I am sure that I checked continuity.

Also ohm-out the actual switch positions before I put something out of place.

Also I wired the Outputs to the CAT PC Board Output.

This one took time, patience and careful planning, heat shrink tubing and good lighting.

See my work in progress below.

Update 8:30pm - disaster strikes a PSU "Short Circuit!"

The HV400 board died RIP, I was working tired.....:(

Well success and failures are always lurking, while failure is usually un-invited.

I was troubleshooting the Left Channel (no sound) and I mistakenly inverted the]

CAT-1 PC Board right on top of the Power Supply board.

The Preamp board short circuited the HV on the Power Supply.

POP!!!! and the small amount of smoke that follows this.

The solid state "spark of death" arrived again after many years.

The puff of smoke and roasted Semiconductor rose from the Power Supply board.

I don't have much free time lately, so I re-ordered the set again from Analog Metric.

This time I plan to replace the WIMA Capacitors with my favorite Illinois MKW Poly Caps.

Hey at least I have a spare boards for future repair issues.

I can attempt to troubleshoot the CAT-1 PC board to find out where

the Left Channel is being lost along the signal path, as all DC voltages are present.

Also I would need to order parts to repair the cooked Semiconductors on the PSU.

Sadly the money to order these piecemeal is 1/2 the cost of a new Kit, I choose the Kit.

The lovely aspect of Solid State PC boards, they are fun to throw into the Garbage.

Troubklieshooting bad PC board traces is not my idea of Fun.

And repeatedly upgrading PC boards degrades them.

Hence I am a Point to Point Wiring advocate.

Now it's waiting for my order to be confirmed and getting the two kits

on hand to build them again. I will post photos of this activity.

It's a shame that only one channel was working as the Signal was lost

somewhere between the 12AU7 and the 12AX7 SRPP tubes. It got late so I just

put this aside until I re-build the boards and re-test.

4/22/24

I re-ordered the CAT-1 Kit Board and also the Power Supply PC Board from Analog Metric.

Once they arrive I will restart this project with fresh new PC Boards.

The original CAT-1 Board somehow has the left channel out, and when I started to

troubleshoot the board "belly-up" it one of the large metal heat sinks short circuited

and ruined the HV400 Power Supply. I ordered parts and when I tried to replace them

the PC board got worse and worse, eventually the traces just melted when I tried

to replace parts. I can tell that these PC boards are not manufactured to be repaired or

have parts/capacitors rolled. These are build once and leave them alone.

I will update this as my time allows and the part arrive.

I dod complete the Input RCA's and the Selector switch wiring, it has proper continuity

and the Shields are all grounded at the inputs. I did my best to cut the cables so they looked

neat, but I have to roll up some small slack and they now are better looking.

MY NEXT PROJECT ALREADY IN THE FINAL METALWORK PHASE PRIOR TO ASSEMBLY

Transcendent Sound Cathode Follower Stereo Amplifier - KIT

Pending project in queue - This is  a mid 2024 build 4 sure; I am pulling out all of the parts and will get this one working by Q3 2024.

I purchased one of the last remaining sets of Chassis and Toroid Transformer from Bruce Rozenblit when he cancelled this product, what a shame, but who can blame, Bruce is out there slugging away, a true innovator. But all of the parts are now at gathered in the large Zip Lock Bag, and a surprise not shown in the picture below. I did not begin the assembly yet, too much of life these days.  But I have one prospective person interested in this when I finally have it connected and making Music. After all, this is the main reason for my love of Tubes, it is based on my love of MUSIC. I lost contact with the interested party so I may just keep this amp as a Single Ended special for Horn Speakers. The 6550 is super smooth, and I expect that in SE it will deliver some good sonics through the One Electron UBT-1 OPT's. Only time will tell. Now that I am connected to Front Panel Express, I will not likely use the blank rack 19" panel shown below. I prefer to order a nice front panel with professional lettering. I will give credit here and make the front panel say "Design by Transcendent Sound". This is one of the Bruce Rozenblit specials and I expect some sweet music...

4/22/24

Chassis painted and Rust-Oleum Paint

I finally painted the Bare Aluminum Chassis with Rust Oleum Paint/Primer Grey

The results were good. I also will paint the One-Electron UBT-1 OPT the same Grey

so the amplifier looks neat, and elegant, with matching colors.

The front panel is still a 2U 19" Rack Mount Black with Power Switch and Indicator Lamps.

I will also install Rack Mount Handles for that extra tough of functionality.

This week, I will paint the Output Transformers and drill out the holes for the Speaker Binding posts.

I will also have to drill out the chassis top for the larger 1000 uF Electrolytic Capacitors

that are three (3) large UNITED CHEMICON, as the major devation from the original schematic.

3x1000 uF is better than 3x560 uF in the Power Supply. I am not cost driven

so why not splurge on better parts?

Start @7:30pm 4/30/24

More Progress on the Cathode Follower build

Drilled out the Speaker Connectors, also installed the Impedance Tap strip 4-8-16 Ohms. I decided against putting just the strip limiting the type of Speaker terminations. Now I can use Spades or Bananas on the Speaker terminals, and securely fasten them. The reamer is how I make the holes glove-fit, I use blue masking tape to establish the reamer stop point, then I finesse the ream until the speaker terminal plastic plates match the holes and snap into them. I love Blue Painters Tape, as it helps prevent the drill bit from walking or slipping sideways, although it always moves a bit. My list includes a benchtop drill press, gosh I love those. Now I don't mind that the connectors have slight differences, it gives my the amps that organic hand made touch, as nothing is perfect, not even a straight line. Completed the rear panel, all done with the parts.

Drill then ream to fit.

Binding post holes, de-burred

Binding posts installed

Front of Amplifier

Rear of Amplifier

Stopped @8:30pm 4/30/24

Next stop, the Hole Punch session for the 1000uF/400V Electrolytics. I will work on this Friday, I have every other Friday off. I can wake up early, play some Acoustic Guitar, then sip some Coffe to then enjoy my morning assembling the Cathode Follower. This amp will be sounding in May-June 2024, I am in no Rush, just want to create a solid long lasting Amplifier. I am so curious as to how different my 2A3 Air Gapped OPT's will sound to the One Electron UBT-1 and 6550 Tubes. The fact that I am doing a Current Source on the OPT Primary will deliver a sonic signature. Maybe I will do something similar with the Kismet 3, put SE OPT in the Cathode? I could tomorrow conne Positive Impedance Tap jumper/spade.

5/5/24

10:50am

Just having some fun, with the parts and the body of the project amp below, the photo is staged of course, no wiring yet.

Next up is to drill and punch out the bottoms for the 3 caps.

I decided to wait before punching any holes on any chassis if you can.

Install the main stuff, then let the build itself,  guide your next step and placement of parts, every one for a good reason.

It allows You to take on you own decisions and lay them out in metal and plastic.

This is how DIY feels, just great, as making new amps that nobody has is a cool place to hang out and accomplish something that lasts.

So when I am no longer around, my amplifier legacy can be divested by the family.

This also leverages the practice makes perfect, I have a roll of wax string that am highly tempted to tie wrap this amp

To tidy up the wiring old fashioned, not Tie Wraps, Wax String.

I also try to, as possible, for every existing screw hole,

to piggy back all of the Tag Boards to existing holes.

Even 6 out of the 9 Capacitor brackets connections to the top plate matched, or slight change in the hole location.

So for every existing hole on the top plate use them first, then drill out any conveniemnce holes to complete the component installation.

The Front Panel will definitely and eventually be from Front Panel Express, but that is mot the current priority.

The priority is to continue to build out amp, working methodically as as close to the instructions, making the notes

as I describe the changes that I made to the schematic, like those professional Electrolytic Capacitors.

That is how true quality gets into DIY amps, what a commercial builder sees as an unecessary cost

the DIY builder fits that right into one amp, not thousands......

Note the old Shuguang 6550 Tubes from the 90's, I got those at Roberts TV Parts in Puerto Nuevo.

The 12BH7 were an EBay score, a real pair of Toshiba branded tubes.

The 12AX7's, these are my surplus from Groove Tubes.

I once bought a case of 100 ECC-83, no markings on EBay from Groove Tubes rejected tubes liquidation sale.

I am still feeding and picking off that stash, some of the ECC-83 are quite noisy.

I also will be taking measurements for the optional custom front panel.

I have a front panel already but am very tempted to splurge on a front panel that makes tribute

to this special circuit. I want to put the Transcendent Logo as this is how we honor the other creative

designers, buying their stuff. That is often the real holy grail tube sound at an affordable price.

And this psrticular Kit has no PC boards, it is 100% hand, point to point, wired, in the purists way. 

I want to use Wax string to sew up the wires, for that classic look when artisanal skills are evisdent in the older products.

Actual Human Hands built these older generation appliances.

Enjoy May, the Month that Honors Mother's all over the world.

HAPPY MOTHERS DAY 2024

5/10/24

I just had to order a cover for the exposed Toroid. Somehow I just wanted a sleeker more finished look. Yes a delay now

as I will not be able to punch the Capacitor holes, until I get this cover in place and bolted. This cover will give the amp a more finished look.

 

The Bro's Amp

Stereo 6L6/5881 amplifier started in the 90's (Not a Kit) - Pending project in queue, lots of sentimental value here as the wood base was crafted by my best friend who passed away in 2012. We had so many plans, and all of them came to an abrupt end when He crossed the Rainbow Bridge. I don't think this one will be for sale. It is going to be some type of new build 4 sure and I am slating this for 2025. I don't have any 6L6 amps, so this might be the one? Or a different type of amp with 7868/7591? and Tone Controls? Currently under planning stages.

This is a project with a long story. It that began with two of my friends in San Juan, many years ago, like back in 1999. We shared the work among us. One friend painted, the other hand crafted a gorgeous solid Brazilian Imbuia base from an old baseboard molding. This is OLD Imbuia, the dark kind so rare these days. Young Imbuia trees are felled in the Amazon at alarming rates and the Imbuia wood is not allowed to reach maturity. I understand that Brazil has limited exporting Imbuia, so this makes the wooden base somewhat rare and beautiful. My part of the deal was to drill and punch the chassis, and create a wall sized plotted wiring diagram of the Schematic in a Point to Point Diagram. The interesting story here, the original attempt to build it did not work. We had chosen a "Para-Phase" Hammond 1650F design from the Principles of Power book. We could not stop this amp from motor boating, no matter what we did. Maybe there was a serious wiring error, maybe not. We even contacted the author of the Book and the creator of the schematic. He confirmed that He had never actually built the amp, so this imparts some doubt as to the design and whether it needed some empirical tweaking or corrections. "Para phase" amplifiers need very careful attention to the coupling of the multiple stages, the feedback value and also the values (poles) of the inter-stage coupling capacitors as these can cause oscillations. We tried every trick in the book and it never worked. I stripped it all down a 3 years ago and currently, I am looking for a 6L6/5881 schematic that speaks to me. What I have planned is to build a Classic Stereo 6L6/5881 amplifier with the same Blue Edcor 4.2K 50 Watt OPT's shown in the photograph below. I have to agree that the amp looks gorgeous, I am expecting the same sonically. This will likely be a Seasonal Fall build as the Leaves start to make raking a popular activity. The tubes posing for the photo below are 6550 Shuguang, 5R4GY RCA and ECC83 Tesla. It needs Power Supply Capacitors and a fresh new look at the Power Transformer that I purchased in Costa Mesa, CA when I was touring that area 15 years ago. I haven't built a Stereo Amplifier other than the Aurora Olson Amplifier, so this is bound to challenge me in several ways. Will this one be for sale? The sentimental value here may prevent me from selling it. But as we all know, everything except health, love and happiness has a price. But.... I would be open to trades for this one-of-a-kind Stereo Beauty, hand made with a rare South American Imbuia wood base hand crafted by a real Luthier.

LET THE FUN BEGIN, THIS IS WHERE THE RUBBER MEETS THE ROAD IN DIY AUDIO

I SHARE EVERY DETAIL, WITH NO REGARD TO SECRECY, PROFIT, ETC.

THIS IS ALL FOR THE COMMON GOOD

This is the year 2002, now 6 years later from 1996 when I built my first Tube Amps from scratch, and time keeps on-ticking.

My website has officially launched from my new home in Puerto Rico, so I wonder where it will be in 2020?

As I launched my 2002 ShermanAudio Pro-Bono Website to the world, I am hoping to share my love of electronics and music, my site should evolve and grow

Note the wiring spaghetti in the last pictures, sure looks like my first project and what a learning experience it was and has been.

Look at the Sprague PIO Caps, VITAMIN Q's, ordered from Cary NC in 1996, they have a liquid presentation, like floating in a swimming pool of sound.

The second to last photo shows 'charred' phenolic board where the original 3 Watt cathode resistors cooked and died, leaving their scorched carbon black fingerprint and a bad smell in the air.

I have had my share of problems with building the 5-20 design, and they still haunt me today in 2002.

If one studies the Mullard book and runs a few simple bias calculations, it becomes evident that the EL34's that were used back when this amp was designed were, and I assume this... very, very robust (just look at the price of Mullard EL34 NOS on EBay).

These amps bias the EL34's at 25 watts of standing current plate dissipation, ouch.

The Mullard 5-20 designers bias the EL34's pairs right up to their full 25 watts plate dissipation, and this is without any music being played.

This left me wondering, where does the extra margin comes from when music starts to playMy wallet was the immediate answer.

It has become evident, after 6 dead and roasted quads of new EL34's of various vendors that the only way I ever enjoyed these amps was with a Variac.

This equated to about 110 VAC on my Variac and I will explain why.

The 5-20 design requires a unique mains transformer configuration and a PSU choke with a DC resistance of 200 Ohms. These were parts made in the 1950's.

Today's Transformers have lower losses and perform better due to improvements in materials.

Also my hidden enemy was lack of experience and the Hammond 278X Transformer. This made 115VAC connected to 125VAC a dangerously high secondary boost so the tube filaments and the DC voltages are scary high, filaments measured 7.5-7.8 VAC rms, not good. The rectified High Voltage DC was totally way off, so high the tubes were dying.

This was all part of my steep learning curve and the death of several matched quads of EL34's.

The Hammond 278X Transformer had 115V Primary and 400-0-400 Volts @ 200 milliamps HV secondary, 6.3 VCT Filament section with 6Amps capacity and a 5 VAC Rectifier filament section with 3 amps capacity.

Slamming a 115 VAC primary with 125 VAC was my hidden enemy, and recipe for cooking EL34's into submission as the Plates were idling at 450 Volts DC not 390V.

One can run 5U4G, GZ37 and other 3 amp rectifiers no problem, but each will have a different voltage drop. One can also convert the power supply to solid state and save on the costs of the rectifier and separate transformer, including the heat given off. Purists may cringe, yet there is nothing wrong with diode rectification as long as one controls the inrush current with a thermistor of soft-start solution.

Judging the variety of killer diodes available today, one is definitely challenged to use them...... tube rectifiers relegated to the boutique aspect of what is at the heart of this tube madness.... the purists would agree.

Yet despite this, the 5-20 amp always ran HOT and eventually, the future would hopefully allow me to get them working normally.

Lets do some math:

So at 470 Ohms and 32 Volts DC drop

This means that (2.17 watts/ 3 watts ) * 100 % = 72.3% of max power dissipation.

Good design practice is to use 50% or less dissipation capacity, so I would use a 5 watter instead, but .... but the 3 watter 'acts' as an EL34 surrogate safety fuse, with a smell that you won't believe! If it cooks, this strange odor varies, depending on what the resistor is made of.

The cathode resistor dissipation decision was probably based on safety for the output tubes, better to lose a resistor than a tube. If the EL34 somehow 'ran away the resistor would fry, open circuit and save the EL34.

A quick calculation will show that the DC current passing through the EL34 will be;

I = V/R

I = 32/470

I = 0.068 Amperes (a.k.a. 68 Milliamps!) now this is strictly Cathode current the sum of Grid and Plate Current.

Calculating the 'Plate Dissipation' will be then be; Power = Voltage x Current

Pd = 390 Volts DC * 0.068 Amperes = 26.5 Watts (Max Pd for EL34 is 25 Watts!) so if I assume that the 'extra' 1.5 watts

comes from the current flowing through the Grid (G2) then I can assume that Mullard 'parked' their EL34's in the 5-20

at the maximum level possible, just prior to the main entry door into 'Red-Plate' land; 25 Watts Plate Dissipation.

Any way you look at this late 50's design, it was obvious that the approach was to put lot's of global feedback and

bias the output tubes hard. This is no longer good design practice, and at that time, the EL34's manufactured were

in my humble opinion probably capable of 30 watts plate dissipation, owing to the dimensions of the internal structure

and physical size of NOS original Mullard EL34's. No current production EL34 is the same physically, the older EL34's

from those days fetch lots of money, now I know why, they can take abuse and work well longer than most

current production EL34 and their variant tubes such as the E34L and also the fat bottle 6CA7's which are Beam Tetrode's and

not true Pentodes. As you can see, in the 5-20, if one does not control the mains DC power supply rail, there will be trouble-ahead,

 just like the Grateful Dead's "Casey Jones".

My conclusion is that the 5-20 was designed back in the Golden Years of Hi-Fi where designers used high plate current's and lots of feedback

to lower distortion and improve the amplifier's full power bandwidth performance, which on the 5-20 is guaranteed to be 20 Watts @ 30 Hz.

Tube amps idle like automobiles, you either get lots of torque, or speed, or a middle combination of both.

The recipe for good sound is where to park the tubes and find the ideal transfer characteristics where Power, Distortion and Frequency Response

all somehow come together at a specific Plate to Plate impedance value, a Push pull sweet spot in other words.

It's difficult to optimize all possible tube parameters but different designs will produce varying combinations of each circuit's merit or problems.

Note that 68 milliamps idle current is close to "no man's land" for any current production EL34. The one's that have proven to work so far are the vintage Tesla EL34, JJ E34L, and Svetlana EL34.

The Sovtek EL34WXT a.k.a. Continental slimmies turn cherry red in my 5-20 after about 70 seconds.

The nipple top Ei EL34 are probably the most dangerous of them all, these tubes will turn red in less than 25 seconds after warm-up.

So many worn-out quads, so many memories of great sound. Now I realize how sweet those dying EL34's sounded, this was before I really knew what

Red Plates were all about.

I suggest that anyone wishing to build a 5-20 Mullard based EL34 amp, consider the use of a 350-0-350 VAC, 180 to 200 ma Secondary with a 120VAC rms primary, 125VAC rms even better.

What to do ?

Well, I plan to find a mains transformer that works at 125VAC rms.

Unfortunately, the 'closest' I could get cheaply were Hammond 278X. This mains transformer has the filament and HV capacity a bit over dimensioned, especially with a primary wound for 115 VAC, not the 120 to 123 VAC typical in today's power grid.

I will have to either spend some real bucks on a Sowter or Electra-Print or ...... re-build on a different chassis and use the Angela universal transformers I purchased some moons ago.

You can follow this link to interesting Mullard 5-20 Schematics plus other SE and Push-Pull amps.

http://www.bonavolta.ch/hobby/en/audio/el34_1.htm

Why Tubes, ... and why D.I.Y. ?

Way back in the late 60's when I was 8 years old and jamming to the Beatles and the Monkey's, little did I realize that most of the music that surrounded me was in fact coming from Vacuum Tube amplifier technology.  When I got around to owning a hand-me down Dictograph Mono System in the mid 70's as a curious Teen-Ager my destiny was defined for me to one day return back to my audio roots as an Electrical Engineer.

Even back then, Hum was always the main problem. Now I know that the Electrolytic Capacitor technology was still in it's infancy at that time, one reason why large chokes and small caps in the Power Supply was the de-facto design standard.

It all began one sunny afternoon in central Virginia looking through some Stereophile magazines that I placed an order for the 'Mullard Tube Circuit for Audio Amplifiers' book.  It took me a while to understand the technical details, not having a real tube background. My degree in Engineering was based on Solid State NPN, PNP, FET, MOSFET and OP-AMPS. Tubes were a similar but different area I had not previously 'academically' traversed and in the 80's were history book technology in college curriculums.

Determined as I was to build the Mullard 5-20 El34 amplifier from the Mullard Book 5-20 Schematic, I began my quest for the ultimate in parts 'scrounging' and minimal investment for pieces, parts, sockets, etc. The nomenclature stands for 5 tubes - 20 Watts. These amps are heavily biased at 68 Milliamps each EL-34 so it's imperative that the EL-34 tubes are able to withstand plate dissipations at their maximum 25 Watt value or else one will eventually see the plates turn a dark red color like a piece of hot charcoal in a BBQ, NOT good.

I recalled that an acquaintance of  mine from a radio project in Volusia County FL, had offered but still not sent to me a paid-for pair of tube amps. After a friendly phone call the mystery $40 amps finally arrived. They happened to be an original pair of completely taken apart and parted-out Leslie Tube amps from Leslie Tone cabinets. One was a Leslie 145 amp, the other a 122 model. Both chassis looked just right for a different kind of amplifier.  So onwards I delved into what was to become my first pair ever of EL-34 Mono-block amplifiers.

This pair of amps took me about 4 month's to build and about 5 years to hone to perfection (or almost there.) These amps are built of original Steel Leslie amp chassis, they did a number on my hole-punches. I finished the pair with some Oak sides and Brass Sheet Metal to cover-up the already punched unused Leslie holes on the chassis.

After extensive listening by the Bros' (my tube buddies) and myself these amps were named 'The Thoroughbreds' by my best friend. After several iterations, tubes and a jump to true GZ-37 rectification from Diodes, their name still stands today as a testament to my first attempt at building some nice mono-block tube amps.

The Mullard schematic on which these were based has some really amazing sound. There are some modifications and extra things that I added to compensate for the less than ideal power transformer I used like an overrated 6.3 Volt filament supply. Each Monoblock uses 2xEL34 Svetlana, 1 x CV378 British Military Rectifier, 1 x ECC83 Groove Tube and 1 x EF86 Svetlana. I boldly took the first two power supply caps to 100 uF each and the CV-378 hasn't complained yet (despite the numerous warnings on spec sheets and tube news sites.

Last night while listening to some music something dawned on me. When one is working or building amplifiers that use Power (Mains) transformers that are rated at 400-0-400 VAC, it's a whole different world out there for the first and second capacitors of the power supply section.

Transformers that provide at least +400 Volts on the secondary will tend to settle down to a rectified B+ DC voltage of 500 volts or higher on the first capacitor. This of course depends on how loaded down the High Voltage section truly is from published Full Load specifications. Therefore I would conclude that capacitors rated at 500 Volts DC are NOT able to safely filter the raw rectifier 120 Hz from 60Hz (or 100 Hz from 50 Hz) without the chance of failure.

Always be safety-aware when designing with 500 Volt tube power supplies that any transformer that provides +400 Volts AC or more on the secondary is an immediate candidate for +600 WV (Working Volts) Electrolytic or Film capacitors as minimum. What I have yet to try is to stack Electrolytic Capacitors for higher voltage handling capabilities. Something about the voltage equalization resistors that doesn't play well into my engineering techy mind. Maybe it's just high voltage phobia playing with good design practices, or the Cabernet I was sipping :)

Today I installed the new power supply parts..... and the amps are once again operational (w/variac). The fundamental problem remains. The Hammond 278X Power Transformer is too much for these Mono-Blocks. 

>Hammond 278X has 200ma, when the original Mullard specification calls for 180 ma. The amp actually draws a steady 147 ma so the mains transformer should not be too large, or else the power supply may need another PI section (Cap and Resistor) to drop the B+ to the acceptable value of 465 VDC. The 278X should be fine, but watch the filament voltage.

>Hammond 278X filament section delivers 6 Amperes AC at 6.3 Volts, this is a bit overkill for a Mono-Block amp that requires 3.5 amps AC. So... the only option was to install some power resistors in parallel with the Filament section to load the darn voltage down to 6.3 VAC from 7.0 VAC. Or light up the amp with enough 0.25A - 6.3 VAC bulbs!

Unfortunately custom wound examples of the required transformer in the USA are as expensive or more than OEM current production models. It would probably be about $300 USD each to have these mains transformers wound. Some people claim that in Europe, custom wound transformers can be found much, much cheaper than in the USA (as stated by another angry rec.audio.tubes forum member), yet I doubt this claim until I can see for myself. Any savings on the product cost is probably offset by the shipping and taxes.

So..... what do I end up doing with my Mullard amps. Running them always on a Variac is not what I really want or the answer to a Home-Brew project. 

After some web surfing I do find that Sowter makes a replacement 5-20 Mains clone to the 'exact' specifications of the Mullard manual. I mean complete with the second 6.3 Volt, 2.5 Ampere winding (for an FM tuner which I do not have.)

I sent a mail to Sowter to inquire about these transformers and the US dollar weakness makes these about a $500 dollar investment, too much for me at the moment.

Finally after much soul and web surfing, Steve and www.angela.com has his Angela Universal transformers that will work well. These should run me about $240 USD the pair including shipping. As soon as these arrive and the amps are upgraded I will let you know what the results are!

4/26/05

These transformers don't really fit these chassis, so I am going to first try to squeeze them onto them and test. If all goes well I will then re-do a new pair of these amps of some bigger chassis and leave these as-is with the Hammonds and the variac. After all these were my first tube amps and the sentimental value is still there. With the Variac I can enjoy the crystal clarity of the Mullard design. Anyone who wants to hear an EL-34 produce some Bass, build a pair, you'll be surprised about common misconceptions on EL-34 and bass reproduction capacities.

5/2/05

The Variac solution works so well that these amps will remain on that device for now. I have other more important projects now and the transformer mod will have to wait.

But I can say that these amps sound totally lush and full with great tone and frequency extension. Despite the feedback level they employ, the sound remains clear-transparent without a hint of grain or veiling. I am using now a quad of new Russian made Mullard EL-34's. These tubes sound marvelous at 62 milliamps each. The JJ E34L's don't sound as good, they are much darker, probably close to being run too hard at 62 milliamps. The Mullard design is taking the output tubes real close to the maximum, yet the new Russian Mullard tubes get the job done in a way that other's have failed, even the Svetlana EL34's. So my recommendation for new production EL34's lies with the Mullard tubes, I purchased at the Tubestore.com. One of these developed an intermitted filament connection. Once again these current production tubes require careful testing and screening beyond what most typical vendors use.

5/18/05

Still using these amp with the Variac. I simply dial-in the correct AC input voltage and put the DC VOM on the first power supply capacitor and match the schematic voltage value. The rest of the amp is 99.9% as the original and the currents and voltage settle-in nicely. At the moment the Mullard re-issues tubes continue to sound totally amazing. If I do anything to these amps, it will be way down the road. But for now my only advice would be to spend the money on a pair of SOWTER Mains Transformers wound to the exact specification of the original Mullard amps in the Mullard Tube Amp book. I can't afford them now but who knows down the road :)

4/4/06

The mains transformer, choke and OPT's are available from Sowter and VVT Transformers. I would highly recommend that at least the mains transformer be sourced from any one of these two places. The Mullard amp draws about 148 milliamps each. Therefore it's imperative that the High Voltage mains section of the transformer, the 410-0-410 VAC be capable of delivering 180 ma or thereabouts. If one uses an after-market mains transformer with the Mullard 5-20, the compromise will be that the DC resistance of the power supply choke will require the mains voltage to be less than 410-0-410VAC. One can probably get away with a choke that has 78 Ohms DCR @ 10H and a mains transformer like the Hammond 374BX. What ends-up happening is that the under-loaded 6.3 VAC @ 6 A section will offset the voltage loss from the HV section. The end result with provide enough voltage and current to meet the requirements for one 5-20 Mono-Block. With the Hammond 374BX one can get away with using a choke that has less DCR than the original design. This improves regulation and also may have some incremental effects of the sound quality vs. a 200 OHM DCR choke as specified in the Mullard Book.

5/12/06

Amazing how so many people are interested in this amplifier design. I plan to re-do these amps as they do sound amazing when working. Unfortunately I will have to modify the original design to 'slow-down' the rate of consumption of the EL-34's. These amps cathode bias the EL-34's at such a high level that a quad will last at most 3-5 month's before burning-out or frying the cathode resistor.

MerryXmas - Happy Hanukah - December 2016 - Happy New Year

12-31-16

I'm back again after a long absence from my website. New Years Eve a fitting day for my return.

My 20th Anniversary Mullard 5-20 Monoblock Amps are playing again.

These are my very first DIY tube amps and as a fact, I had once thought of taking them apart.

My dear Wife told me not to, she told me that I would regret it some day.

Well words of Female wisdom and here they are, revived on Xmas Eve and now playing on New Years Eve into 2017 and beyond. Classic Vintage EL34 High Fidelity from the 1950's; Sweet!

On the 24th I had to order a quad of new Cathode Bias bypass capacitors.

WHAT CHANGED?

The solution at hand was to swap the original Hammond 278X power transformers out for a new Hammond model that made these amps come together like the Beatles! I still have the pair of 278X, e-mail me for a price, I will sell the pair. Note that 115V Primary limits the design center.

I ordered a pair of Hammond 273BX this year (summer) and the project just sat there looking at me every time I walked by, a reminder of how procrastination just sits there in the open, it never hides, it just nags.

There were two separate sessions prior to Dec 24th. One was to take apart all of the small things that I had done to the amps and also to fit the new parts.

NO MORE PROCRASTINATION

On Dec 24th I got some coffee and grabbed the amps after some prior work sessions fitting in the new changed parts and fitting the new power transformers.

A NEW TWIST

The new Hammond Transformers offers an electrical means to select between two AC Mains Voltage primary taps; 115V and 125V.

Being able to select between two primary voltage windings allows for amplifier power correction and the stability over long term use, especially on Cathode Biased amplifiers that have ne means for voltage control.

There are two ways to choose the setting of the AC Primary Switch.

If the DC voltage across the 470 ohm resistor increases past 32V on the 125V setting this means that the AC mains voltage is very, very  high at your Outlet, so if you cannot get anything lower than 32 Volts DC on the 125 Volt AC position I would recommend getting a Variac.

I would never again operate the Mullard 5-20's with anything greater than 32V DC across the Cathode Bias Resistor and more than 25 Watts on the Plate. I prefer standing each EL34 plate dissipation at just 22 watts, not 25 watts.

Leaving a few watts of headroom on the plate and extending tube life. This does somewhat change the output impedance of the EL34 tube pair but the effects are mostly and almost inaudible. Yes one can measure shift of the Mullard operating point but as long as they are less than the maximums we are in the safe zone.

If the DC voltage drops below 32 Volts DC this means that your AC Mains voltage is at or below 125V. I like to save the tubes so I will almost always operate these Mullard 5-20 amps at the 125VAC setting and be done.

Note that running the amp with 115V Mains on the 125V setting would create 'dirty sound', not enough juice from the Power Supply, it starves the amp, but will still play, just lacking fidelity at higher power levels..

The whole amp just relaxes on the 125V tap, like it went from Cardio to Yoga. I will provide the final voltages in a Table below so we can see that using a 350-0-350 VAC vs. 400-0-400 VAC was more about several things than just a high AC voltage.

The 115V Primary of the original Power Transformers made almost 600 VDC with no load!

I needed to tame this down and tested the amp with some spare transformers and found that the best compromise was the Hammond 273BX was the best center design.

Today's transformers are more efficient due to improved wire and materials quality.

ONE LAST POOF!

As I was upgrading and testing the amps on Dec 24th, one of the 47uF/50V Cathode Bypass Capacitors exploded in a dark smelly smoke with lots of fluffy paper pieces. The part was 10 years old so it surprised me to have it fail.

I ordered (4) Nichicon Muse 47uF/100V Electrolytic Axial Capacitors that arrived in record time, 2 days.

MULLARD 5-20 OBSERVATIONS AND CONCLUSIONS

I highly recommend the Hammond 5-20 in stock form despite all of the articles and suggestions to the contrary.

First I like to respect a designers work, so sticking to the original schematic makes this possible, of course with a few small substitutions of equivalent parts for a design from the 50's.

The EF86 input gives the amp tremendous musicality and gain. Yes this is not the ideal to work with Preamps that have more than 15 dB of gain.

Make sure that you use a quality 1 Megohm Audio Taper Volume control to make this another nice feature of adding a Volume Control so a Preamp is not always needed.

These amps are perfect for iPods and Smart Phones, given the correct cable, the EF86 tube recovers the goods and delivers them in clear perfect form. No need for a Preamp here if you want to use a Passive.

The EL34 tube has a sound character that appeals to me, especially on voices and instruments. The design of the 5-20 offers great damping.

You can make a pair of these from parts all available today, and now that I figured out the perfect pair of Hammond Power Transformer and Output Transformer, the build is easy enough. You will need to create the tag boards that Mullard describes in their manual. This makes assembly much easier than the random tag-board point to point method (I also like).

Note that I built these on real Steel Leslie 147 Chassis. Unless you are able to find a pair of gutted Leslie amplifiers, I suggest that you use one of the many powder coated Hammond Steel Chassis. You will need metal hole punches for the Octal, 9-Pin, Capacitor holes and Drilling skills. Two metal reamers help tale each metal hole to the ideal size manually, by fitting the part and reaming until snug. 

Although I like the sound of an amp in a steel chassis, aluminum is much easier to work with.

Note that on my 5-20's the power supply choke is the original 5H, 75 Ohms Leslie 147 Choke. But you can easily order any one of Hammond Chokes from 5H to 10H and 50 Ohms to 100 Ohms. The series resistance of the choke will slightly skew the resting (quiescent) Hi DC+ voltage of the 5-20. Yet with the ability to choose between 115V and 125V taps on the transformer primary, I call the new feature Hi and Lo mode.

ABOUT THE 115V/125V SELECTOR SWITCH

Reviewing what I have previously stated above:

The new Hammond taps empowered Primary SPDT switch ON-ON with AC Power Cord Hot (Black) wire through a 2A Fuse then to the center lug on the switch. The 115V and 125V taps solder onto the outer lugs.

A 20 YEAR JOURNEY AND LEARNING EXPERIENCE; LISTENING TO THE CIRCUITS COMPLAIN!!

This my fellow DIY lovers was the source of my 20 year struggle with these amps, I had started with a Power Transformer that was highly over dimensioned at 115VAC with no 125V tap. Even though the secondary voltages and currents were okay, a combination of using the original specs in the Mullard manual and the suffering of the tubes using this Transformer with 125 VAC on a 115V Primary.

My memory has me recalling quirks like EL34's making physical noises when warming up. Not to forget the many Red Plates on 80% of the EL34's I tried. I killed a few good quads during my steep learning curve.

My troubles are finally over. These 5-20's are playing through the new year, as I sit here at 10:10am on December 31, 2016 mission accomplished.

I set my self the goal and managed to get these amps going on their 20th Anniversary after 10 years asleep.

As I remember, building these amps in my basement and filming the process (video will be posted soon) back in late 1996 at Connecticut Ave. in cool Lynchburg, VA. Yes I actually filmed the build, it brings back lots of good memories when I was learning about Tubes and Amps on my own.

The 5-20 amp, although simple, has lots of complexity. The circuit design is superb and the specifications for music enjoyment are about all one needs with a pair of efficient speakers, an iPod/DAC and a bottle of nice wine.

New for 2021:

I refreshed the amps, changed out the legacy PIO caps and re-did the Cathode Resistor and Electrolytic Capacitor for Hi-Temp ratings.

The pictures and sound speak for themselves... now both amps measure identical with the tubes all tested and matched.

UNDERBELLY OF THE CURRENT MULLARD 5-20 AMPS, THE TAG BOARDS ARE BUILT JUST LIKE THE MULLARD BOOK

A CLOSER LOOK AT EACH AMP

A SHOT FROM THE SIDE AS ONE APPRECIATES MY SIMPLE EARLY WIRING SKILLS, MUCH IMPROVED OVER TIME

       First generation Kismet - still sounding fantastic - Audio Note OPT's are SE-2.6K-20W - VTV Top rated value

I substituted the 6922/6DJ8 for a 6N1P. The 6N1P is a better driver for the 2A3 Input Grid, the Bass is far more refined.

This is how the Kismet looked in the original build from 1999, it is far cleaner and less cluttered now.

Below is the Kismet today in 2021, amazing sound only the 2A3 delivers, the 45 would be in my opinion the 2A3 kissing cousin.

Now the 300B is the showoff bully of the Single Ended cult. Certain speakers just amaze me with the 2A3 but if you need more Body to the music, 300B is King.

The absolute most realistic vocals I have heard was with my Lowther PM6C Minitowers from Classic Audio and the Kismet 2A3, my Dog would Bark...

My Pug would stand-up and look around when people spoke through the Lowthers.

Caveat.... Lowther Driver Cones are so pure, they do not do well in Tropical Climates.

In a matter of 6 month's my PM6C's went from stark paper White to a yellow old Diploma color.

The Lowther surrounds rotted in less than 1.5 years in the Tropics.

I would have to assume that Lowther Drivers are "pure & organic"

Just sharing my decades of Tropical wisdom for those wanting to enjoy Lowthers in the Caribbean.

If you plan to spend on good Stereo gear in the Caribbean, dedicate a Music Room, and buy a De-Humidifier.

The Star of the show: Real Audio Note SE Output Transformers...very special indeed, makes music like very few OPT's can

The Story of the original Kismet Amplifier

Here is the latest Kismet article from Fabio Camorani. I will soon post the schematic for my version above. The topology was based on the original Kismet but the circuit was re-worked to have a 6N1P driver tube and also a different Power Supply scheme. We find the new schematic with the 6N1P Russian input tube to offer much better control in driving the 2A3 than a 6922.

Here's a link to the Kismet amp and the original designer.

http://www.positive-feedback.com/Issue1/kismet.htm

Back in '97-'98 I was reading many things on the web. Hence one of these was the SE amp phenomenon which was destined to become part of my future. My curiosity about those 'flea-powered' SE amplifier web sites drove me to build one for myself. 

So.... after subscribing to Glass Audio, an article arrived in the mail.... The Kismet article suddenly popped into my life and I was very intent on making one for myself. So I decided to build a replica of Fabio's design as best as I could despite my lack of parts.

I ordered a pair of Audio Note 2.6K 20W SE Air Gapped Output Transformers and one Power Transformer from Angela Instruments that was a Horizontal mount N.O.S. Chicago Transformer model. Little was I to know the importance of the quality of the mains transformer in an amplifiers sonic signature. This transformer is still today dead quiet and marvelously black in the background. Too bad Steve and Angela sold out....

The Kismet's name was already decided directly after the article in Glass Audio by Fabio Camorani who as I see now, has already evolved the Kismet into a version 3. My Kismet also evolved, but in a different direction. 

Kismet is Arabic for 'fate', and what fate for me to experience +50 pounds 3 watts RMS!

The sound of a single-ended 2A3 amplifier is very sensuous yet tonally correct. Not for the average person, but for the limited bunch of audio radicals who build 50+ pound 3 watt amps and match them to ridiculously expensive high efficiency speakers like Lowther and Fostex. These full range drivers offer the most 'idiosyncratic' sound there is. Now don't get me wrong but low powered SE amps are not for 95% of the people out there. Even though I read that Tony Robbins built one himself. But those who claim that Lowther and Fostex drivers can be a good match for 100 Watt Solid State or Tube amps are probably in the business of selling repair kits for blown and overheated voice coils.

The photo shown is the Kismet as it is today. It took me 48 hours to assemble and 3 years to really hone this SE amplifier together. The final version has a 6N1P Sovtek Input tube instead of the 6922 Sovtek. With the 6N1P I can have 170 Volts on the plate and 5 milliamps cathode current vs. the 6922 that provided much less drive. I hear the 6N1P as a definite upgrade to the sound over the 6DJ8/6922 types. A 5R4GY NOS rectifier and some Sovtek 2A3 single plate tubes completed the project. This amp will only move speakers that have sensitivities in the +94 dB and higher range. Anything lower and one really has to crank up the volume to get a satisfying soundstage but the music collapses and the definition gets lost.

I committed one sin in that I use Global Negative feedback (10K resistor) in my Kismet. The feedback resistor I believe improved the overall sound quality of the lower bass region and also improved the upper midrange as I now hear less glare.

My hats are off to the designer of the Kismet for having inspired me to pursue this wonderful tube audio hobby armed not only with a soldering gun, but my calculator and graph paper as well!

7/8/04

I now have in front of me (5) ECC99 tubes and the Kismet is ready for the next modification, take out the 6N1P driver and replace with a ECC99 JJ. Now that I have this in front of me, I have on order a pair of Kiwame 820R 5 Watt bias resistors soon to arrive so I can once and for all upgrade, tie-wrap and consolidate this amplifier into the reference 2A3 that it always wanted to be. One of the next mods is to add a Headphone Jack for private single-ended bliss and Balanced Connections on the rear panel for testing with a Ralph Karsten preamp!!!

7/23/04

Last night I opened up the Kismet and replaced the series 500 and 300 (800 Total) Ohm Cathode combo as seen in the 'belly' photo a 'Brown Ceramic Tubular' in series with a '5 watt - 300 Ohm Sand' Resistor. The Kiwame 820 Ohm, 5 Watt precision resistors from Parts Connexion look real 'beefy' and to me, promise to lower any distortion artifacts that the other resistors may have introduced in the cathode circuit. The extra 20 Ohms (800 vs. 820) probably made improved the bias level for a softer (more negative) voltage drop across the Cathode for a Vintage 2A3. I will measure to check the value of the bias and also the plate voltage as well to fix the operating point on graph paper. Some tube rolling also caused me to re-visit my Sovtek 2A3's again. It was obvious after 15 minutes that the Sovtek 2A3's were crying for the 5AR4 rectifier in place of the GE 5R4GY Brown Bases. The 5AR4 radically changes the DC voltage distribution causing the amp to run hotter and the tubes to draw more current. I have designed the center points in this amp to be able to accept any suitable rectifier. My Power Transformer has un-loaded taps so the 5 Volt, 2 ampere rectifier section easily handles 2 and 3 amp current draws. All I can say now with the 5AR4 is that my next report will be the ECC99 mod with the 5AR4. The sound of the Sovtek 2A3's confirmed that these tubes are a bit more robust than standard Vintage 2A3 tubes in both bi and single plate configurations. If I run the Sovtek 2A3 at the normal operating point for a standard 2A3 they tend to sound just a bit glassy and edgy, as confirmed by a tube that is over biased (i.e. running a bit cold). To next drop the ECC99 in place of the 6922 basing (6N1P in my case) I need to re-wire only the heater circuit. There is a need to jumper pins 4 and 5 together and move one wire from either pin 4 or 5 to pin 9 to make the socket a ECC99/12AU7 base. Tonight, I will drop-in the ECC99 biased at 6N1P level to do a first check. Maybe I will need to change Plate and Cathode resistors to optimize for the ECC99, the sound and my VOM meter will indicate just where the ECC99 has settled. I will undertake the mod prior to my first cold Beck's and report back mid next week. I will also post the photographs of the upgrades and just maybe.... the ECC99 will be there as a permanent improvement for a Kismet in it's ever evolving state. As I acquire experience, so do my home made amps also benefit. The more I know, the better they sound.

7/28/04

Oh well, not all that glows glimmers! The ECC99 'upgrade' was attempted without positive results. I adjusted everything from the Cathode, Plate and series dropping resistors to attempt to 'squeeze' the correct conditions for the ECC99 driving a 2A3. If failed due to distortion, noise and a terrible buzzing sound when connected to my system. The only resistor that I did not play with was the 100K 2A3 Grid resistor. I just may eventually place a 500K rheostat linear potentiometer in series with a 47K resistor and tweak the tube into submission. But this is only an assumption on my part that adjusting this resistor should tame the ECC99.

Well to turn a frog into a prince I paid attention to optimizing the 6N1P taking the plate voltage up a notch and replacing the cathode and plate resistors. In the plate I used 24K and the cathode I used a 390 Ohm (old carbon 1 watter that actually measures 500 Ohms) and the results were nothing short of a real nice upgrade. I also replaced the Cathode bypass capacitors for 100 uF Nichicon Muse for a smoother more relaxed presentation. The 6N1P was a 120 uF and the 2A3 was at 220 uF, and they were 'cheapo' electrolytics for transistor stuff.

How does the Kismet sound now, like heaven. The Kiwame bias resistors now come through and it is evident that in a simple design as the Kismet, parts quality is immediately audible. Now that I am on a roll, I will re-do the Kismet front panel in a tasteful way. I want to simplify the panel, remove the VU meters and take it down to bare essentials. I just may add a Cathode bias control (or take the design to Fixed Bias?)

Pictures during the re-build of the Kismet. My last mod will be to change out the front Panel altogether without the VU meters. I want to install a nice Power Switch and a Painted Logo that says "Kismet" in some nice color, probably not the white it came with... or maybe I will just leave it as-is...

4/26/05

I am going to build another set of Kismets. One will be using the new James 8 Watt Orient Hi-B OPT's from Euphonia Audio. The rumor is that the other one will use Tamura or Magnequest. The one with the James Transformers is under way but the other one is pending parts ordering and conformation from the buyer. With not too many days at hand and all my travel its a real challenge to build amps and have time to relax.

Stay tuned as this 2A3 phase promises to be an interesting ride. We will be able to compare the sound of the Audio Note's and the James as well as whatever the other buyer intends to pay for the output iron!!

This Kismet will sport a new front plate and a simple look. New pic's coming soon

Kismet taken from it's original state of parts bin assembly ready to be upgraded with better components and some different value electrolytic capacitors. Much smoother sound was obtained.

Original Kismet above as it was originally built.

Now below is my second generation Kismet 2  - James OPT's Model 6115-HS, sounds.... nice, but not as refined as the Audio Note SE OPT's. Maybe sounds a bit more dynamic? This amplifier was given away to my very close friend Rick Elias. The current status is unknown. If you ever happen to come across this amplifier, you can rest assured that you can get information by sending me an e-mail.

8/21/06

It's been 1-1/2 years from the last report.....

KISMET-2 is working!, last night I completed the project. One thing about living in the tropics, everything here takes more time than when I was in quiet Lynchburg VA. Project's here in Puerto Rico take-on a life and price of their own, and the main topic is a combination of Heat, Humidity, Procrastination, Laziness and the high costs of shipping. Also I lack a workshop, sort of like a Formula 1 Driver without a pit area. Every time I want to work on something, my apartment goes belly-up in wire, parts and cusswords as I step over things. This amp is a keeper for now until my buddy decides to re-prioritize some pending issues. I can knock-em out in a matter of weeks, but tweaking the amps to perfection takes month's and even years. Small projects take me only days to assemble and with a dedicated shop this will be the norm.

Note the James transformers and the gorgeous "Yaeger Audio" chassis that look very good together. I highly recommend http://www.yaegeraudio.com the Yaeger chassis for your next DIY amp. John can even have the chassis pre-punched for convenient assembly. These black Powder-Coated chassis are A#1 in quality, they save lots of time and make lot's of sense for first time DIY enthusiasts. Not even Hammond makes such nice chassis, or a complete solution at that. This chassis comes complete with IEC Cord socket, fuse and removable top and bottom covers. Also the bottom cover is ventilated! 

6/8/05

Never say never to company travel. Now I have another workshop in Central America. It's back from a three country trip only to take off this Sunday to another country. But.... instead of pouting ....last night after reading a RAT post from John Yaeger, it pushed me out of inertia. The post got me going into the assembly mode away from the whining mode. 

Yup, I was able to 'masking-tape' the top cover and began the process of marking the panel for drilling, filing, and reaming, .... heck whatever one calls going at sheet metal with home tools. The pics coming soon after I get my camera charger from the lost and found. I surely hope to have this Kismet 2 amp ready before the end of July. I will focus on this goal and at the same time complete my Dyna-Clones.

7/28/05

Yup I'm back again after travel, vacation and catching-up at work. The process of cutting and punching the holes on the Yaeger Audio chassis has commenced. The chassis aluminum great to work with and very thick, enough to support heavy components. The 2A3 sockets have been a real challenge to mount from below, the hole punch with a proper diameter is hard to find locally. I bought a metal punch locally sourced for 1" conduit (1-11/32" hole), this happened yesterday at Roger Electric in Carolina, PR.  The hole results about 2/64" smaller than ideal, but this is easily machined with my Dremel tool into a glove fit for the 2A3 sockets. My other amp was made by using a caveman hole cutting drill bit approach, what resulted required the 2A3 sockets to mount from the top to cover the mess in my original Kismet.

The through the chassis transformer square cut was amazingly simple to make. The metal cutting jigsaw blade sawed right through the aluminum chassis with amazing precision and a simple wood like feel. Wow! the Yaeger Chassis is a real deviation from all Steel Chassis that are a real nightmare to cut and drill.

I am almost thinking that aluminum may be a better material for Tube Amps. My only aluminum amp is coincidentally the Kismet first generation and it sound smoooothhhhh.

With some hi-temp flat black to match the James Transformers, the Kismet 2 amp should be working in no less than 2 weeks time or less, that is if I am not sent away on business travel again. Stay tuned, I am full steam ahead on this project.

8/1/05

Surely was a productive weekend. On Friday evening I almost completed all of the chassis drilling. The Dremel tool was invaluable for shaving in 64ths of an inch holes that were just a fit too small. Now the 2A3 sockets are mounted below the chassis, and the punched holes were taken to a glove-fit.

On Saturday I took the Power Transformer and Choke over to my best friends house for a paint job. The Power Transformer is an old Chicago Transformer purchased about 7 years ago from www.angela.com, the same as on the original Kismet.

The Choke is a Hammond 8H/150ma and also can use the same paint job. Most of today's Hammond transformers look pretty ugly as the painting and finishing quality is at best 80% there. Unlike a pair of Hammonds purchased 10 years ago that had a much better finish. Well enough with the Hammond bashing, they have good products and a heck of a range of models to choose from.

As soon as the Transformer and Choke are ready, I will post the cosmetic external amplifier snapshots. The internal wiring will take me several days as I plan to make this amp an example for a production model later on in the near future.

8/9/05

It keeps raining, and raining and raining here in Puerto Rico. At over 85% relative humidity getting anything painted is futile. As soon as the weather breaks, the transformers will receive the final coat of paint and new photos will be posted.

4/25/06

A day has 24 hours, a week has 168 hours and a year has 8760 hours. Once the replacement Hammond Choke arrives I will build the amp and tweak it until I can say that it sounds like the Kismet 1. I am very curious as to the James Transformer performance, yet something tells me that the Audio Note's probably sound a bit richer in the Sonics department. My plans are to complete this project no later than end of May-06. My friend is unable to produce a painted choke despite my patience and waiting now that has turned into month's. I will not allow this project to become a white elephant like my 6550/KT-88 amps that took years to complete because I was depending on other people. One common factor on all of my project delay's was my company travel and my dependence on other's to get work done. It's the "Hasta-Mañana" syndrome taken to the next level..... :-)

5/12/06

As soon as the choke arrives, this amps will be sounding in less than 4 hours time. I will pre-wire as much as I can and await my order from Angela Instruments.

5/2/05

Guess what..... I am building a new Kismet using James OPT's. The OPT's are the small James that promise to produce some interesting sound. Coupled to this is the http://www.yaegeraudio.com chassis that are 90% complete, all I need is to punch some holes and get the metal work completed end may. These should be ready soon. Pictures will follow. Another friend of mine wants a Kismet was well. When he gets around to buying the parts I will reciprocate with third version, maybe different than what I currently have and the Kismet 2. It's may very well be a duplicate of Fabio Camorani's Kismet 3 that employs fixed bias and a number of critical improvements that promise to create Single-Ended magic once again. To date no one has ever complained about the sound of the amplifier pictured above. Even when it's not even warmed-up the Kismet has the ability to pull one right into the music, the 2A3 is a tonally correct tube. I have not yet heard a 300B amp that sounds as good as the 2A3, then again I know there has to be an amazing 300B amp out there, I just haven't been lucky enough to listen to one. If one can live without deep bass, the 2A3 SE amps are very sweet sounding.

5/4/05

I replaced the feedback resistors in the Kismet. Instead of 15Kohm I installed 22Kohm. This lowers the level of applied negative feedback and opens-up the sound of the Kismet. I will install a switch for the purist types that believe it's a sin to apply negative feedback to any SE amp design. Yet to my ear a little feedback goes a very long way. I notice the Kismet looses control of the Bass at high volumes without feedback. With the feedback the lower and upper frequency extremes remain very stable until clipping which then makes the Kismet amp sound loose and hard. After comparing the sound of the 300B to the 2A3, I have to say that I prefer the 2A3 sound over the 300B, it's clearer. After the summer, I am may have to build a Stereo 45 amp to have another toy to drive my Lowther speakers with. No name for this amp yet, but It shall be a product of my own design using SE CAD.

2/17/21 report;

I purchased a pair of EBay James Output Transformers just like the Kismet 2 back in the winter in Feb 2021.

Gosh, these parts are getting more difficult to buy and much more expensive.

The pair of James are of a Light Grey Hammertone finish.

Today I have only one Power Transformers left to build another Kismet, and I plan to kickoff the build in Winter 2022.

Also, still have the last Yeager Audio Kismet 2 style chassis, so I will make the Kismet 3 an evolution to version 2.

The Kismet 3 may have a few differences, and I am thinkng to make the Kismet 3 have "fixed bias" instead of Cathode Bias, let's see what happens....

Only time will tell...

SR-91 AURORA 2022 THE FINAL CUT

NO DOUBT, IF YOU PLAN ON BUILDING AN AURORA, REST ASSURED, THIS IS THE CORRECT STEREO POWER AMP PLATE AND FILAMENT POWER TRANSFORMER.

DESPITE THE 115VAC PRIMARY, I ACTUALLY DESIGNED THE AMP AROUND THIS POWER TRANSFORMER TO WORK GREAT AT 120-122VAC.

IT IS THE LUXURY OF CONTROLLING THE DESIGN AROUND WHAT IS CLOSE ENOUGH.

COMPROMISE IS GOOD AS LONG AS LARGE AMOUNTS OF SPECIFICATIONS ARE NOT DEGRADED

THEN YOU CHECK THE FINAL DESIGN!

ALL PART OF LEARNING TO "PARK" THE PARTS ON-HAND.

POWER SUPPLIES AND THEIR LOAD SETTLE AT A QUIESCENT VALUE

MANY TIMES IT TAKES SOME FINAL ADJUSTMENTS TO MAKE IT PERFECT.

Below is Gen 1.0 Aurora with Green Triad S-42A Opt's!

This version lasted a few years........Enjoy the Launch, Apex and Splashdown.

 

Original Aurora with Vintage NOS Magnetek-Triad S-42A output transformers, good iron, but not quite Hi-Fi. This was version 1.0, I was learning how to design from scratch...

Circa 2014 improved Aurora Version 2.0 with Hammond 1645 output transformers, better sound, musical and detailed. I also installed some Hammond Secondary Wiring Switches so I have on the fly 4-8-16-70V Taps all at the turn of a switch. Also used better value Power Supply Chokes that give the amp a nice boost as I had parked the 6F6 tubes is a conservative zone. In the photos below the impedance selector swithces are shown in the 'bellu-up' photo.

THIS IS THE FUN PART, LOOKING AT THE UNDERBELLY THIS PHOTO IS FROM 2021

I installed the Hammond Transformer Output Impedance Selector Swiches

SR-91 Aurora Power Supply sketch - Updated from a prior revision new 2020 revision from 2006:

Update Feb 3, 2019

After many years of enjoyment, I re-visited the design while looking at the ratings of the Russian 6F6 Tubes. I determined that I really could drop the series resistance of the Power Supply Chokes down and squeeze a few more volts out of the DC supply. I went from Hammond 159M to 156M that meant a reduction from 256 Ohms down to 86 Ohms DCR. This allows more headroom to the amplifier circuitry. The fidelity improved. I have not measured the output power but my last measurements were 10 Watts per channel into a 100 Watt 8 Ohm Dummy Load.

I now use 5V4 and 5Y3 tubes, as sonically they are a better match for my ears. The 5Y3 I use now is the SOVTEK... robust indeed. The original 5Y3 has a 125mA Max. The SOVTEK can handle 135mA no problem.

The only difference in this sketch, the 5AR4 don't sound as good as 5Y3 so I am using the Aurora with 5Y3 and 5V4. The parallel series impedance of the 5AR4 do not match well with the power supply topology. Also the Power Supply chokes were also updated to lower ESR chokes, allowing the 6F6 tubes more headroom. I pulled the 159M and replace with 156M. I still have the 159M's in case anyone needs them for a project.

THE FINAL POWER SUPPLY WORKS BEST WITH 5Y3 RECTIFIERS, AND LOWERING THE DCR OF THE CHOKES DID MARVELS FOR THE HEADROOM, WOKE THE 6F6S TUBES UP, THE SOUNDSTAGE JUST GOT WIDER AND DEEPER. THIS IS AN AMP WITH IT'S OWN OPINION OF HOW MUSIC SHOULD BE AMPLIFIED. MOST FRIENDS WHO HAVE BORROWED MY AURORA CLAIM THIS IS MY BEST SOUNDING AMPLIFIER ? SO THE NO-FEEDBACK CLAN MAY HAVE A POINT.

Now enter the original Aurora build experience >>>>>

MENTALLY YOU MUST TRAVEL BACK IN TIME TO EARLY 2000 PUERTO RICO, HOT HUMID, EXCITING, BEACHES, MOLD, HURRICANES... THE TROPICS.

http://www.bonavolta.ch/hobby/en/audio/6f6.htm

Now for my third home brew project I had purchased a clean empty aluminum "aluminium for those from the UK" onto which I wanted to blend art and science into what was to become one of the most interesting projects in my life.

The only positive thing to come out of REC.AUDIO.TUBES.

So back in 1995 I visited my mother back in San Juan, Puerto Rico. Due to the fact that vintage parts and tube stores were already disappearing in '95 I decided to visit trusty old 'Robert's TV Parts' on De Diego Ave (still open for business) in the Puerto Nuevo Metro area. I managed to buy a NOS pair of Magnetek-Triad S42A 4.5K 50 Watt 4-8-16 Non-Ultra linear output transformers triode 'three wire primary.' Now that I had the iron, I needed a schematic. What was I to build with this iron ? after spending 120 dollars for the pair!

These transformers went totally dormant at that time as I was building the Mullard amp as I needed 6.6K Primary OPT, so the 4.5K did not inspire me to experiment so I saved them for a rainy day. Plus the Mullard amp needed an ultra-linear transformer (five vs. three wire primary.) So these transformers traveled all the way back to Virginia where they remained and returned back to Puerto Rico in December of 1996.

Eventually, in late 1998 sometime after Hurricane George I surfed across a schematic on the Claudio Bonavolta web site called the 'Olson Amplifier'. And guess what, it required a 4.5K primary, non ultra linear OPT, just like my Magnetek. At first I was taken back by the use of 4 x 6F6 tubes in the output, knowing quite well that the Glass Version 6F6G and 6F6GT were hard to source and not sure whether I wanted to build a metal tube amp.

But I endeavored and voila, I built the Aurora Amplifier and it was aptly named the 'Aurora' after a classified High-Tech Pulse Propulsion Plane that some say does not exist. Well the my Aurora does exist and here it is in all its 14 tubes of glory.

The amplifier uses Hammond Transformers and Chokes, the S-42A Magnetek Output Transformers and the following tube lineup:

8 x 6F6G (Russian 6F6 glass version), 2 x 6SN7 Tung-Sol's, 2 x 6J5 Fivre Italy and to finish things off 2 x GZ34 German RSD. 

How does Aurora sound, well I can only say that going from 6F6 Metal Tubes to the Russian 6F6G was a revelation in clarity, the glass tubes taking the upper hand. The last upgrade was to install dual 15H, 100 ma, 262 Ohm DCR chokes to really smooth things out. These chokes added a level of dimensionality to the sound that I find hard to describe in words.

12/22/04

Last night I decided to fire-up the Aurora again after a period of calm dormancy. The first thing that I did different was to replace the GZ34 rectifiers with 5Y3. My original design was based on dual 5Y3 so out came the GZ's and in went the 5Y's.

I did not measure the voltages, but I can surely tell you that the 5Y3 rectifiers in this amp provide a far more textured and layered sonic presentation. With GZ34's installed the rectifier section runs at 50% capacity. But.... with 5Y3 the rectifiers are working at their designed capacity of about 110 milliamps each, max is I believe 125 ma for 1 tube. With two 5Y3 in parallel the Voltage Drop must be about 30 volts across the rectifiers instead of the usual 60 Volts for one tube.

So here is the Aurora. As you can see I spared no expense in using top quality parts for a real no-costs-barred approach. All that is left is to have a custom cage built and complete the project by installing the Bass Contour and Volume Controls that were on the original schematic.

4/22/05

Well time to improve the Aurora. After extensive listening over the past several years I have decided to improve the Aurora. These Magnetek-Triad S-42A output transformers are beefy, yet only provide 30Hz to 15 KHz performance. I know what you are thinking, that it should not make a difference to put a 30 KHz capable transformer, but I think it does. So I ordered a pair of Hammond 1645 5000 Ohm 30 Watt transformers. The S-42A transformers may go up for sale to interested parties who want to buy a pair of "Greenies" and re-paint them to suit the application.

4/26/05

Basically in two separate sessions, one mechanical and the other electrical, I completed the upgrade to the Aurora last night at 11:30 pm. Initial listening tests confirm a bit less output power from the new 5000 Ohms Center Taped Hammond', yet this was fully expected. But the improvement of sonic inner detail and pure 'listen-ability' was simply superb, the noise floor went straight down to the basement. 

Opening cut of Keiko Matsui's 'A drop of water' was as dynamic as I have ever heard, and the lushness of the opening of Acoustic Alchemy's new CD release American/English made me smile like an idiot at 11:45 pm after a session with the soldering iron and a cup of warm Earl Grey and Honey. 

I am very satisfied with the Hammond output transformer line, but cannot say the same about their Plate/Filament products. 

Hammond OPT's are consistent products and perform very well. It's a real pity that their line of standard, classic and plate only power transformers do not have practical secondary voltages and capacities for Stereo amps, but very odd combinations of Plate and Filament sections that either require one to compensate or design around them. Extra's such as filament loading resistors and voltage dropping PSU sections may be required to pad down the typical High Voltages that Hammonds provide.

Furthermore the Hammond power transformer line does not sell anything that can be used to create a practical Stereo EL34, 6550 or 5881 Tube amp on a single chassis. Either the H.V. is way under or over-dimensioned for mono-block operation, or the filament current capacity is way over dimensioned. One can end up cooking tubes for as an un-suspecting DIY enthusiast. 

Despite this a strange amp like the Aurora was made a reality by a Hammond power transformer I picked that was almost a custom fit design, owing this to the eccentric nature of the Hammond designers and their current production line of Plate and Filament Transformers. I have sent several mails to Hammond about this but no response has ever been received.

5/2/05

After an extensive listening period I do conclude that the Hammond OPT was a success. I would recommend that you give this amp a spin, but try and design the amp with current production tubes, not the rare 6F6 like I did. Yet if you can get your hands on a quantity of the Russian 6F6's go ahead. This amp sounds neutral and un-colored, flat is the word I use. It works well with and without global feedback. At the moment I am using a Brown-Blue-Orange 1/2 watter bypassed by a 330pf mica cap. The feedback tames the upper frequencies that can be very bright with no feedback. But i think that I need to reduce the feedback level by increasing the resistor in the loop. Maybe I will change it to 22K vs. what I have currently installed. Or maybe I will put a potentiometer and have variable feedback. The final mods will be to install the Volume and Tone Control that were on the original schematic.

5/1/07

Two years later and the Aurora continues to play well. I decided to completely eliminate the Global Feedback. The amp did not need it and originally, the designer did not implement this. What I can say about this amplifier is the following. Such a platform would make an interesting amp that uses 6V6 tubes instead of 6F6G which are hard to find today.

Left Channel Mono-Block

Right Channel Mono-Block

What to do next? I asked myself this question many times before engaging my next home-brew project. After having struggled with so many tag-boards and swapped parts, I decided to go all out on a pair of 6550/KT88/KT90 Monoblocks with the Triode Electronics MKIII upgrade circuit board.

The name Tornado comes from the pair of British Pilots who were shot down due to friendly fire in the recent Iraq conflict. After the Kismet these amps already have names before their launch date. I chose to honor these fallen warrior pilots as they were willing to give the ultimate sacrifice.

As these Monoblocks will be based around the Dynaco MK-III Upgrade Boards from Triode Electronics. I expect to save time in wiring by using these flexible upgrade boards. In addition, I am also using the MQ-782 Dynaco Replacement Magnequest Transformers! I expect these replacements to be superior to other equivalent transformers. There was a specific Hammond model that I could have used that sported a 50V vs. 60V Bias Tap, but I feared a restricted bias range. In a pinch I am sure that the Hammond's would have worked fine with the proper adaptations.

The center piece of these amplifiers will be the output transformers. A pair of real Potted M-Double C-Core Bartolucci Model V 4.3K 60 Watt Ultra-linear Microcrystalline impregnated transformers. Wow! I can't wait to bias these up with some KT-90's and letter-rip.

As these amps are currently under construction, I will be adding pictures of the whole process from parts to my planned Chrome Plating of the chassis. If the chroming place permits I'll be taking some pictures there as well.

As you can see I started by placing all of the parts on my workbench and went straight into the Masking Tape process to simplify drilling and help guard against most scratches. If you follow the sequence of pictures, it will give you an idea of my approach to putting together some tube amps from scratch.

7/16/03

I decided to solder the 9-pin Ceramic Tube sockets directly to the PC boards. The original strategy was to mount standard 9-pin sockets to the chassis and to run cables to the PC boards. This was because I plan to do allot of tube rolling. These MKIII boards can accept, with a special filament switch design (worked this out already) either 6N1P, 12AU7, 6CG7 and 12BH7 tubes in the V2 position.

This requires that I install the PC board under the chassis with metal standoffs that are 0.625" long so that the board under the chassis and the sockets line-up flush with the surface of the amp base. This I believe is a better solution in the long run, keeps wiring down to a minimum as originally designed.

Visiting my friendly local New Electronics Center Store on Fernandez Juncos Ave. "BTW -The place is for Sale" also picked up a pair of Shurite VU Meters identical to the one's I used on the Kismet amp. I am real tempted to 'add' the tube based low level driver circuit shown on the Shurite VU Meter instruction sheet. This keeps the VU meter out of the secondary side of the transformer. This is still under consideration at this moment.

In addition, as I plan to install a 'dual-bias' configuration on each Mono-Block, I ordered today from Allied Electronics four Model 3307 Shurite Panel Milliammeters. This will allow me to install a DC current bias meter per KT88 (6550) so that I can read the bias current directly from the meters. It's far more 'real-time' than having to fumble with calculators and volt-meters. I can always install a meter shorting switch to take it out of the circuit, besides the Shurite specification is 1 Ohm DC Resistance for the meter. Does not hurt to leave them permanently part of the Power Tube cathode circuit.

Once the parts arrive I will continue the construction process. Thanks for visiting The Music Room!

8/6/03

Unfortunately 'the company' that sent me the 1-3/4" Sheet metal punch sent it Fedex 'Ground' to Puerto Rico... duhhhh! Did they think that Puerto Rico was driving distance from Kansas? Due to this, I have the project on-hold until the sheet metal punch arrives. I cannot continue the project without knowing how the (4) large metal can caps will fit prior to doing anything else. One must not indiscriminately make holes in any chassis unless the complete picture of how the parts will fit is at hand! Stay Tuned..........

8/11/03

Still waiting on the Hole Punch vendor!! Apparently the company moved to another state and the new 'operation' is not as efficient as the older one. So much confusion to send one Hole-Punch, geezzz. I had placed several days earlier, two orders from other vendors that were received just days later. Seems like the company that I buy my Sheet Metal punches from has lost the 'edge', let's see if they can get the part to me soon. 

I will be away on travel until early September so the Tornados will face a hiatus for now. In the meantime, one piece of good news. My friend has a plasma metal cutting system. This means that I will be able to make the 'square' holes required for the Shurite 100ma meters. 

As I mentioned before, I plan to install Edgewise 100 ma DC meters, one per power tube. This way I can have a visual indication of cathode current while I measure the DC voltage drop across 1 Ohm resistors in the cathodes. Note that I say 'Cathode' current as it's the sum of the Plate and Grid currents. Some folks don't realize that on Fixed Bias amps the grids will draw some current often making the amplifier operate in class AB2 vs. AB1

I may just install the meters in 'series' with the Plate leads from the output transformers to the plates of the tubes. But.... floating milliammeter's at such high voltages does not give me the 'warm-and-fuzzy' feelings that I like to have when I build stuff. Let me investigate this and I will get back to you right here in 'The Music Room!'

8/18/03

Unbelievable, still waiting on the 1-3/4" Hole Punch! Heck, if Greenlee made that specific size I would have gone to Grainger weeks ago! Now I am stuck again waiting on a 'phantom' Fedex delivery. The vendor finds it impossible to send to me the Fedex Airway-bill number unless I ask repeatedly. I am about to 'cancel' this order and get the punch directly from the EOM in the U.K.! This is one example of an order that has gone seriously wrong! I am on 3 weeks travel so the Tornado delays continue.  As some people believe ' Good Things Take Time.' I did snatch a quad of KT-90 Type III on Ebay in the meantime! Thanks again for visiting the 'Music Room!'

9/3/03

The 1-3/4" sheet metal punch finally arrived!!  Seems that 'The Company' (I won't order from them again) insisted on Fedex ground from Kansas to P.R.? This meant that Fedex does 'not' do the local delivery, another company takes this role?.?.? How confusing can they make things! Anyhow, I have been away for 3 weeks now on company travel and arrive back home this Friday the 5th of September. 

Current plans are: Complete the physical assembly of the chassis, then go to my buddy's "Plasma Metal Cutter." I want the square holes for the DC Milliammeters to be as sharp as possible. Whether I install VU meters is still up for debate. But probably not, as they require 2" round holes on the front of the chassis inevitably weakening the already 'more-than-twice' perforated chassis.  Besides, I can use the VU meters for some other Preamp project down the road!

Will post more photos after the next round of metal work! Thanks again for checking in with the 'Music Room!'

1/7/04

Signs of life!!! I'm back after such a prolonged hiatus. As you may recall the 1-3/4" Hole punch fiasco took so much time to get here that it threw the whole project out of schedule. Over the holiday's I have managed to continue the chassis metal work assembly of the Tournados. 

From the pictures you can see that I managed to install the Oil PSU capacitors from www.angela.com which are actually motor start capacitors converted into a DC filtering application.  I have to believe that these capacitors have to be a marked improvement over the standard Electrolytic types, and over twice the size at that!

The PSU caps were so big indeed that I chose to mount two of them thru-the-chassis and the other two under the chassis. They lined-up quite well underneath. In addition, I also aligned the Octal tube sockets also from www.angela.com after having securely mounted the PSU caps. It is always better to go step-by step, from the larger to the smallest components in any amplifier project. First mount the Transformers, then the caps and the terminals and finally the Octal Tube sockets. One then finishes with the tag and turret boards located strategically for under chassis wiring layout purposes.

This time around, I believe that I hit a bulls-eye as the Power Tubes and the Rectifier Tubes have very good clearance between themselves allowing for much cooler operation and prolonged tube life.

Now I will be concentrating on getting the rectangular holes for the Shurite 0-100 ma Milliammeteres (one per power tube) machined to exact specifications on the front panel of the chassis. This amplifier will feature one meter per power tube so I can read and adjust the bias idle current on each Power Tube individually without having to fuss with Tip-Jacks or DC Voltmeter voltage drop readings across known power resistors in the Cathode. By installing permanent bias meters I can always 'see' the bias current and will immediately know if there is any problem developing as the Power Tubes age and the bias begins to drift.

I have included the latest pictures of my project. The bottom received some rubber feet and the top cages were also drilled and fitted as well. I will post these pictures and the larger versions of the newer series as soon as I get the chassis back from the machine shop.

Until the next report, keep jamming and enjoying the Music Room!

1/11/04

Update..... Today is a national holiday in Puerto Rico, Eugenio Maria de Hostos. I called the machine shop and they were open.... Hooray! 

I took both Hammond chassis and one single Shurite 0-100 milliammeter into my favorite machine shop a bit after lunch time. The name of the place is "RO-MA Welding and Machine Shop, Inc. / (787) 767-1406." 

Mr. Rodolfo Mayol's machine shop is located at the end of the 'golden-mile' in Hato Rey.  Many a time I took to Mayol's raised floor tiles from communications rooms for drilling 2" to 3" round holes. If you are familiar with these types of tiles then are double heavy gauge metal with a cement filled interior. Not the job for the average drill-press!

I spent a good 30 minutes with Mr. Mayol explaining exactly what I expected. Basically the rectangular holes I need machined need to measure 1-43/64" wide x 33/64" tall (1.672" x 0.5157"). 

Mr. Mayol said that he would have to manually make the holes and finish them with a file. Let's see how they come-out. He promised them to be ready next Saturday the 17th. Heck I could have gone at this with my saber-saw and saved some $, but I know that the finish would have been rather rough. Ideally these types of rectangular holes should be 'punched' out by walking a rectangular punch machine across the hole and finishing the burr's off with a file. Mayol did not avail of such a machine, and Sescom is in Kansas, too far and expensive to send the chassis out for this task.

In the meantime, I plan to begin to paint the DC Chokes and Power Transformers the same 'Volvo Silver-Grey' Inboard-Outboard Motor paint to match the chassis. On the Bartolucci transformers, my plan is to simply apply some elbow grease and wax it up with some high quality wax. 

There are some 'cheesy' cursive Black-Gold labels on the Bartolucci transformers that I plan to hopefully remove if I can do so without damage to the Gloss black paint finish. If not they stay put.

Enjoy the Music Room..... see you soon!

1/19/04

On Saturday the Machine Shop was closed....., I should have called before driving out there. Today is Martin Luther King holiday so I am not sure whether they will open or not. Let's see,,,,,

1/23/04

Having been raised in Puerto Rico, sometimes we may get a feeling that our personal priorities do not match other's priorities. Today I stopped by the shop, nothing, nada.

The chassis and meter are still on the table where I left them.

Patience Richard, lots of patience, 12 day's worth of patience! This is what we Puerto Ricans refer to as the "Ay Bendito!" clause, a sad story about how one is so busy that the work is late.

2/4/04

Well, I picked-up the chassis as nothing had been done to them. Guess it's me, my drill, files and the Dremel tool.  Stay tuned until further notice on my progress!

3/8/04

Due to my ongoing move and living out of cardboard boxes I must say that the project is now on Hold until after I move into my new house. This will give me the extra time to have the chassis machined properly for the rectangular holes needed by the milliammeters.

5/19/04

Wow, I'm back from a world of distractions. All of my things were boxed-up since late February. I have since moved into my new condominium and have now started the process of un-packing. My first order of business will be to make space for a work area to continue the project. With my current travel situation, it will challenge me to finish this project by midsummer.

7/28/04

Heck, I have to be honest, the chassis are at my friend's house now. My buddy has a plasma cutting system. With this he plans to slice-out the rectangular holes so that the Milliammeters fit snugly. Once these holes are cut it's a simple matter if soldering and wiring time before I fire these-up!

12/16/04

I am a bit embarrassed by the lack of progress on this, my latest project. But nevertheless I'm back again. After going through my EL34 Monoblocks and revamping them to near perfection, my gaze is turned towards my second home brew mono-block set. The chassis are the same as before. My friend got caught-up in FEMA work (it's been a busy year for those people) and now I am focusing on getting the square meter holes machined and the chassis chromed or maybe gold anodized.

My week of vacation starts on 12/25/04. Maybe by then I will have the chassis ready for the chrome job. Once again, stay tuned.... The Music Room!

1/11/05

Just a bit of insomnia tonight.... (it's 4:45 am, Tuesday).

The chassis were taken to the premier machine shop in PR, TEMSCO.

The owner and two machinists spent about 15 minutes going over my requirements. All looks AOK for these chassis to be ready soon.

Also spoke to Caribbean Electroplating and once the chassis are ready to be plated, the owner promised to show me their complete line of electroplated finishes.

I think that these amps should be ready by end of February the latest.... but this has been one long ordeal. As soon as I deviate from an all home-brew project, delays are introduced. If it was not for my being so critical about the electronic meter holes, these amps may very well have been built with Tip-Jacks and some calibration resistors in the cathode.

My patience is at the very end now, but I do see some light (music) at the end of the tunnel.

I just may put this pair up for sale..... or they just may be keepers. It's coffee time!

1/12/05

Voila, called and they are ready to be picked-up. Friday is Pay-Day so I will wait until then as I don't know how much this job is going to cost me. Next stop is Caribbean Electroplating. My plans are to have several items electroplated as well so I can get a better cost/work/price ratio. I will post photos of the machined chassis for documentation purposes. I ordered an extra 10 MB of web space as I am already close to 19 MB/20 MB and often receive warning messages from my ISP to delete some files or PAY!

KT-88-6550-KT90-MONOBLOCKS...... COMING REAL SOON RIGHT HERE AT "THE MUSIC ROOM!"

1/13/05

Couldn't wait (you probably guessed that already.) I picked up the chassis this morning at 9:30 am sharp. TEMSCO did a very professional machining job. The masking tape is even intact, this must have been done with a special sheet metal cutting tool.

Anyhow, tonight I am putting the amps back together physically (as in the photos above) and am going to sketch the preliminary wiring plan. This will enable me to install the final tag boards and bias potentiometers to complete the chassis metal cutting.

My next stop will be to Caribbean Electroplating in Cataño (Barrio Palmas), Puerto Rico. Over the phone the owner was very nice to me. He spoke at length about the electroplating process, which went pretty much over my head. Hints at several types of finishes in different colors makes me very curious as to what this would look like in the end.

At the same time I will also drill and punch some ventilation holes in the bottom covers. The metal cages I plan to paint with a matte-black BBQ paint which looks very smart and resists heat.

It's amazing why I did not take these chassis to the best Machine Shop in Puerto Rico in the first place. My gratitude is extended to Ing. Cegre for understanding the needs of an eccentric-eclectic hobbyist. I am sure that TEMSCO enjoyed working these Hammond Chassis as much as anything that they have done lately. I even had to take all 4 Milliammeters so they could custom fit each one to the chassis in case variations in the dimensions of the meters would cause mis-alignment of the mounting holes. If they ever knew how loud I can crank-up "Reise Reise" by Rammstein, they just might have sent me home.

I am on my way to Bartolucci Heaven! My friend has several Quads of KT-88's, one of these if a JJ Blue Glass type. With so much riding on these amps, it's only natural that my anticipation for how the Triode Electronics boards sound as compared to a real Dynaco MK-III is killing me!

1/18/05

The photo is posted above showing the Machining of the chassis for the Shurite 0-100 ma edgewise meters. Each 6550/KT-88 will be fused with a 100 ma fast acting fuse. In case the bias ever climbs past 100 ma so I don't ruin the meters. Project under way again, soon to be more photos!

4/26/05

As soon as I return from my next business trip, I'm diving head first into these amps!

5/2/05

I leave to Sweden next week so I begin this project when I get back towards mid-May.

HAPPY NEW YEAR!!!

3/15/06

Wow!!! I say Wow!!!

It's been waaaayy too long, +10 month's to be exact. My last update was last year. Time flies when we hit middle age!

I had lost my Web design SW so I finally have Front Page 2003 loaded and I am happy to be back.

The KT88/6550 Mono-block project is sounding! I am pleased to say that the amps are 100% complete.

Somehow over the Xmas holiday's I managed to pull myself together, plug the soldering iron in and after a series of decisions on paint and inner layout of wires, tag boards and other goodies, this set the stage for final assembly.

I left the original Hammond Grey Powder Coated finish alone, messing with this meant a questionable spray paint job in tropical humidity.

By masking taping the chassis for the drilling and holes, I inadvertently saved the original paint job. When I pulled off the masking tape, lo and behold a practically scratch free coat lie underneath. Just a bit of Goof-off and they were as good as new.

Next the decision was to lightly sand and paint all the transformers with BBQ Hi-Temp paint a flat black. I used Krylon paint. The results were OK.

The amps were to be put together with the parts at hand, no more orders (so I thought.)

Needless to mention now, when I opened-up the 4 x Shurite 0-100 ma Edgewise meters from their boxes, to my dismay the Machine Shop had somehow damaged all four of them probably through some rough handling, my best guess. One meter looked like it has been opened-up and repaired, it simply fell apart in my hands. I assume that this particular meter had fallen from a height not kind to analog meters. This is probably the point when I received a phone call to take in the other three meters as they argued that they were necessary to complete the work, huummmm... now I know why.

As all four meters were broken, it was then a matter of calling Allied Electronics with my Credit Card for another 4 pieces. The total cost of machining 4 square holes and one of the crooked was now over $250 USD. It's a sad scene here in San Juan. Lot's of talk, very poor quality.

Once I assembled and wired the amps another 3+ weeks of troubleshooting followed. There were strange noises from the speakers, Svetlana Red Plates, and those small quirks such as loose wires, cold solders, loose speaker and RCA connectors plus a 'fried' 10K AC Splitter Balance pot. I am happy to say that all these issues are now resolved.

These amps are heavy enough to limit my moving them around. Each time I have to pick one-up, I breath heavy and hope I don't throw out my back. Not sure about their weight, but they must be about 40 lbs. each.

These Mono-blocks sound absolutely amazing. It's nice to step-up to the 60 watt/ch category after years of 35 watts/ch.

The Dynaco MK3 Triode Electronics PC board, and some good quality parts the project have come to their proper conclusion. I must mention that in my amps the only electrolytic capacitors are in the dual bias supply kit, also purchased from Triode Electronics. The main P.S.U. capacitor values are identical to the Vintage Dynaco MK-3, but these are Oil types ASC 30uf-20uf-20uf-20uF motor start caps (I think they are for Motor starting) purchased from www.angela.com.

With my ear flush to the tweeter, I can't hear the stereo-typical Tube Amp hiss characteristic of my other Vintage tube amps. The only other amp I own that is quieter is my Stereo 2A3 Kismet amplifier.

The front panel layout consists of a Red Pilot light,  AC ON (Radio Shack), a green LED light (Radio Shack) is connected to B+ via a 150K 2 Watt Resistor to indicate PSU cap charge and discharge. It also acts as a Bleeder for the PSU when the amps are powered down off. An internal 6.3 VAC/.25A lamp and lamp base (Radio Shack) illuminates the meters.

The two Shurite meters display direct Cathode Current. Each meter is bypassed by a toggle Switch (Radio Shack) to effectively remove the meter from the Cathode circuit when listening to music. Each small toggle switch places a short across the meter, thus connecting the Cathode's direct to DC ground.

The Bias controls are located in front of each power tube. By rotating these CCW the cathode current increases, CW decreases this current. These controls are a rather intuitive way to wire the pots, the rotation of the control follows the meter movement.

If you want to build a pair, just let me know and I can help with any advice and tips. You can save money by using all Hammond transformers. Yet I highly recommend spending extra on using the Triode Electronics Dynaco MK-3 Power Transformer and the best Output Iron you can afford.

This amp is a foul-proof unit and works very well. The PC board saves lot's of hassles and headaches.

My only regret...... not using Digital Milliammeters on the front panel. Yes the Analog meters are nostalgic, but they have some issues, especially when mounted on steel chassis. This brings me to another point, I would build these amps again on Aluminum Hammond Chassis or have Jon Yaeger build and machine some ready-to-go chassis. Aluminum material is easier to machine and is a non-magnetic.  But I doubt that the Aluminum Chassis from Hammond would have the gauge to properly support the weight of the Transformers and Choke. Jon's products do have the thickness, especially the top panel, believe me they are beefy.

Preamplifier Unit

For the curious about what that toggle switch in the rear does, here's the Aikido's grounding scheme with the Pin 1 problem solved.

 

Power Supply Unit

Below is my experimental Power Supply. I designed this around the Power Transformer Secondaries. I replaced this circuit so it was a phase in my experimentation.

What I did learn was that Power Supply Regulation plays a major role in the sound of the equipment.

This Aikido power supply came about due to the Plate and Filament Transformer. The 10V Secondary Windings was a non-standard voltage, so I used this to light up 12X4 tubes. I enjoyed this for years as I was able to flip the switch and go from Regulated to Un-Regulated. It swas this capability that allowed me to realize how impactful the power supply was on the sound of the preamplifier. I decided to replace this with a dual choke, unregulated design. This was in my mind an experimental thing that was part of my journey into Tube Power Supply design. The power supply was replaced in 2021. So a 13 year run was not a bad thing.

As you can tell, my Electrical Engineering skills Gone-Wild. I learned that simple is better...... I took the Power Supply apart and re-did it with Dual Chokes and a NOS Plate-Filament Transformer.

Power Supply Upgrade in 2021

Working from the momentum of my Guitar Amp, I upgraded the Aikido Power Supply. Once I get into the flow, I always manage to pull projects from the queue.

This queue is years deep, so I may pull something that has been waiting for 15 years or 6 month's. Me, I always have projects in my agenda, having things to do keeps Me active.

I gutted the original power supply and decided for sheer simplicity and added a second Power Supply Choke.

Removed the UTC Transformer and replaced with a Triad NOS I was saving for some 6227/E80L Mono-Blocks that never happened.

I also removed all of the wiring related to the Regulation and just made the Power Supply a Dual-Choke 5Y3.

In the Preamp itself I swapped out the previous 1uF Signal Caps and now have a pair of 0.22uF PIO Caps (they are almost like VitaminQ) and the music just flows.

Then eventually I splurged for a pair of 0.33uF TFTP VCaps, and OMG, these VCaps are the cats meow.

The Preamp sounds great now and I can hear less background noise than before. Simplicity has plenty of virtues and I will always be leaning towards less parts and less wiring.

The Power Supply settled down at a tad over 300 Volts DC, like 308 VDC, so good enough. I went to Hobby Lobby to purchase a aluminum plate to cover all of the holes I had made, it worked perfectly.

The 300-0-300 Triad has extra headroom so I added a second Choke to the Power supply and settled on am 1800 Ohm 10 Watt resistor to finish it off, but ideally 1900 Ohms would have shaved off those extra few volts.

I also replaced the old DC cabling umbilical with an Octal setup and have better gauge wiring for AC Filaments and DC B+, I remanufactured the umbilical cord with good THHN Stranded 18 Gauge Wire, sweet stuff.

See the results below, cleaner, better, simpler and sonically superior.

When connected to my Kismet 2A3, the sound is exotic, holographic, and really stunning.

Amazing what 3 Watts of SE Power delivers with the Zu Druid speakers, they literally disappear into a tapestry of Class A goodness....

POWER SUPPLY RECONFIGURATION IN 2021, FOREST VA.

WENT TO A TRADITIONAL 5Y3 POWER SUPPLY WITH "DUAL FILTERING" AND A OCTAL PLUG/SOCKET FOR THE UMBILICAL CORD. SIMPLE IS BETTER, AND THAT IS THE RULE THAT MAKES ELECTRONICS RELIABLE OVER TIME.

KISS = KEEP-IT-SIMPLE-STUPID.

PREAMP UPGRADE AND CHANGES 2021

 

AIKIDO UPGRADE REPORT 2022

8/13/22 10:30am

Vcap installation day wohoooo..... the V-Cap box arrived at my doorstep yesterday afternoon.

I scored a pair of TFTP at 40% discount, people this is a once in a lifetime opportunity to buy TFTP Vcaps at these last time buy prices.

Once they are gone, they are gone and you will have to buy the Copper Foil versions that are costlier (better but more expensive).

LINK TO V-CAP SALE: https://www.v-cap.com/tftf-capacitors.php

I went from a 0.22uF NOS PIO inherited from a Cary 300B repair, upgraded to a pair of V-Cap 0.33uF/600V TFTP

Sound check later today, I have errands to run, will be back with a report.

Photo below just installed the Vcaps and cleaned up the wiring on the PC board.

I am driving today to Buffalo NY to tour the Martin House - Frank Lloyd Wright's 1907 Masterpiece of modern turn of the Century design

8/13/22 4:45pm

After closing my jaw, and taking a first sip of a Kendall Jackson Merlot, the sound with the V-Caps is much, much better.

There is now zero grain on the music, the purity of the sound rivals all of my preamplifiers.

No going back, these V-Caps will stay put. I have one thing to say about V-Caps, they put an end to Capacitor 'rolling'

Once I budget for V-Caps and install them, I have never felt any reason to remove them from the circuit.

I have spent hundreds of dollars on other competitive brands, and nothing to date over the last decade compares to V-Caps, zero hype.

Mr. Venhaus is a humble genius, and our world needs to place immediate orders for a dozen of these gifted Engineers whose talents and vision

inspire us to do better.

The photo below also shows the relocation of the +300VDC and 6.3VAC braided cables to "under" the PC board, something I wanted to do for a long time.

Yes I fixed that broken RCA Input 3 Wire, but I haven't taken a new Photo.

ALL I CAN SAY IS THAT VCAPS ARE THE BEST VALUE FOR THE MONEY.

The answer to the troubleshooting question from my Home Page:

Left #3 channel RCA Jack Center Pin input wire broke off, and was dangling behind the second 6SN7 from left to right, this happened when I worked installing the V-Caps.

Also the V-Caps are reversed, the Outer Foil is (Green Lead) connected to the High Impedance side (Output 250K Potentiometer), even the best make errors... :)

The Outer Foil should be connected to the Low Impedance side and on this PC Board, it is the 6SN7 Tube Outputs (150V).

Now the Inner Foil (Red Lead) is connected to the Preamplifier 250K Volume Control, thus Preamp Output. Did it make a difference, Yes, the Preamp is a bit quieter...

My point here is this, troubleshooting is most of all, a visual exercise first, before diving into anything that is not working, look, look and look again.

So many times, the equipment is telling us where the fault lies, and we can often hone in on the problem visually before taking things apart.

THE JOHN BROSKIE AIKIDO PREAMPLIFIER

The best kept secret in DIY Line Stage Amplification

My Aikido is a truly modern 6SN7 Line Stage, built on the older John Broskie Stereo 4x6SN7 PC Board

You just can't go wrong with an AIKIDO Line Stage, it is Neutral, it does not get "in the way"

Below is the latest awesome "all in one" Broskie Aikido PC Board.

You can build one of your own super easy.....

Just get a good Metal Box with some good parts and voila!!!

https://glass-ware.stores.yahoo.net/ailiam.html

My single PC Board version has the following design features:

Separate 5Y3 "Dual Choke" Power Supply w/Vintage Triad Transformer

Just recently a major 0.33uF TFTP Vcap upgrade, major... indeed, jaw dropping.

VCaps are worth the money, after 100 hours they just disappear...

I liken them to removing the front door or your house, they let every single nuance enter

the House. I also have VCaps 0.22uF in my Dynaco PAS3x and I cannot say that I have ever heard

a PAS like mine, completely fresh, totally original, modern parts and exact values.

 

A PC Board "Lesson Learned" from a Dynaco PAS-4

I have a story about a B-Stock Dynaco PAS-4 Preamp. The Preamp was purchased new by me as a B-Stock from Audio Advisor back in 1998, most likely someone returned the unit and the factory worked on it to sell as B-Stock. Well that PAS-4 was a Tube Gobbler, the 6DJ8 were operated a bit over their Plate Dissipation Limit so I was rolling 6DJ8/6922 every 6 month's. Also the Right Channel was intermittent and it would come and go as it pleased. The PAS-4 had great Sonics, and awesome controls, it was dead quiet.

Well 'lo and behold', after weeks of measuring, tube rolling and heating solder pads on the PC Board, I decided by pure luck, to inspect the full PC Board with a 100 Watt Bulb that was placed behind the PC Board so I could look for anything out of place. THERE IT WAS, a shiny bright light I was looking at.... a mini white beacon.

It turned out to be a Plate Resistor on the Right Channel that had one PC board resistor lead completely bone DRY, No Solder.

The Resistor lead was just floating in the PC board hole with no Solder, barely making contact with the PC Board eyelet surface.

Very small vibrations would cause the high voltage to intermittently connect to the Resistor lead by pressure and hence the channel drop-out.

So out came my Soldering Iron and problem solved. I sold the PAS-4 to an Italian guy, and in "true-to-form" Italian style, totally nickel and dimed me on the Shipping Costs. In the end I lost money and He thanked me for being a Gentleman. In reality I just wanted to get Him off my back. I even re-wired the Transfomer Primary for 240V, and He did not undestand me when I told him that I was going to modify the preamp for 240V and include a Euro Cord.

When He received the Preamp, He was so glad to suddenly discover that the Preamp worked on 240V, when all along I was e-mailing Him that it was a modification I needed to make.

Oh well.... English/Italian & E-mail, mafungul!!!

In troubleshooting, experience plays a role, and nothing can substitute actual hand-on.

-ROZENBLIT GLASS AUDIO PREAMP BUILD - This one was a weird project usind Radio Shack (R.I.P) parts for the Power Supply. It worked OK, but I would not implement a back-to-back Transformer configuration again for permanent use.

This is what I love about the DIY audio community, there are plenty of good designs and PC boards to stuff.

With this Tube preamp project I wanted to achieve a level of success that my first attempt didn't.

My first DIY preamp project had a great Line and Phono Stage circuit but a bare bones power supply.

Coupled to that, the aluminum boxes in which they were built resulted in many compromises as they were too small.

As you can see, I rummaged through my parts bin for this project. I can start by saying that this was fun,,,, well maybe, more of a learning experience as you can see by the photos and schematics of my first foray into Preamp land....

Rozenblit SRPP married to the classic RCA RIAA Phono Circuit.... worked.. yes, noisy, yes, power supply CHEAP...

I learned my lesson, never skimp on a power supply. Below is my 2007 Preamp project. Somehow it worked, but the performance was not there.

Preamps are about the most frustrating projects as noise is everywhere. Building a preamp one learns about wiring topologies, hum, component placement and all the extras.

As you can see from these photos, I also installed a BENT AUDIO 50K Alps Stereo Remote Control unit on the Preamp. Any couch potato will vouch for this option. The Aikido is a great design.

Mr. John Broskie who designed the Aikido circuit is a very clever designer. Building on existing topologies, John will see things and is able to come up with upgrades to and positive changes on existing circuits and topologies.

Where I find the Aikido a good Preamp baseline is in it's ability to present a relatively neutral sonic character, with low noise and high performance.

I would put most of the effort into building the best Power Supply possible, as the Aikido design speaks for itself. As far as board stuffing, I feel that nothing short of best premium components is a good idea. Heck now that one is spending money on a Aikido PC board, why not put in the best stuff.

In my Aikido board I have 100% Tantalum Resistors, Mundorf Silver/Gold capacitors and top of the line NOS JAN 6SN7WGTA tubes for  a marvelous sound and musical texture.

Here is the Aikido Power Supply which was mostly defined by the power transformer I had on hand, a NOS Military Encapsulated UTC.

After several weeks of tweaking, I had to install a separate filament transformer as the winding section of the NOS UTC simply did not have enough extra capacity and the filaments were running

starved at 5.5 VAC. Now that I put in a TRIAD 4amp model, the filaments are operating from 6 to 6.2 VAC.

Project Parts List

THIS WAS, AND STILL IS, THE ABSOLUTE BEST TUBE KIT PHONO STAGE, MINE HAS ALL MY UPGRADES:

THE 6C45P TUBE, SIMPLY LEAVES MOST TUBE PHONO STAGES DUST IN THE WIND.

This amazing Phono Stage was discontinued. Yet, I am holding on to mine like NRA members hold their AR15's. This is an underrated product, and our Audio world seems to ignore non-mainstream companies such as Transcendent Sound. I am a huge fan of Bruce, He is a clever Engineer with a knack for Tube design. Bruce gets tubes and spins out amazing new products, not just re-creations of past designs.

Now when great products like these, lack the marketing power, hype and budgets, they go unnoticed and un-reviewed.

So I built this Kit back in 2005 and have upgraded a few things.

  1. Poly Coupling Capacitors, low cost and super musical. The kit came with Orange Drop caps.

  2. Phono Loading Resistor Barrier Strip.

  3. Updated Phono Cable Ground Lug, the kit came with a bare bones screw and nut.

  4. Dual Bourns 100K Audio Taper - Output Level controls. When using MM Cartridges, this preamp has such tremendous headroom that these allow optimization of output levels.

The magic in this Phono Stage is in the design, and the use of the 6C45P tubes and the 12AX7 output stage. The output stage can drive any interconnects at even ridiculous lengths.

I have kept a pair of Sovtek 12AX7LPS since the day I first turned this on, and they are on duty until they wear down.

The Noise floor level in this Phono Preamp is likely among the lowest in the world, for an all tube phono preamp, where Tube noise in the RIAA stage is always a challenge.

This this is remarkable coming from a designer, who lacks a huge budget, and does Kit sales as His side Business (Mr. Bruce Rozenblit - Tube Audio Wizard).

If Iron Chef had a Tube Designer version, Bruce would be the Bobby Flay to Beat!!!

The only thing that I will eventually change, is to design and fit inside, a Tube Rectified HV Tube DC Power Supply, that would elevate this unit as musical as it could ever be.

Over the years I have grown to prefer Tube Power Supplies with Tube Circuits, there is an 'elasticity' in the DC rail that makes it far more musical than dry Diodes.

The resistor loading barrier strip allows me to adjust the cartridge damping for best performance.

You would be amazed at what a difference the value of the loading resistor the cartridge coils are connected in parallel makes.

I can transform a bright Moving Magnet Cartridge, and drop the 47,000 Ohms resistor down to 39K, 33K or even 22K and make the top end smooth and sweet.

My last mod, I added a pair of Bourns 100K Output Level Pots to be able to adjust the Output Gain to better match the Preamp input level. I believe that sonically the ability to set the output levels on this Phono Stage is absolutely necessary when using MM Cartridges. If the Cartridge has 2mV or less, then the gain of this Phono Stage is Ok. But when using Grado, Audio Technica, etc.that offer 4mV or greater, having the ability to adjust the gain allows for proper gain scaling into the preamp or line stage.

I just love this Phono Stage, it runs circles around all of my current phono stages and I have let all of them go. This is my reference RIAA Phono Preamp. I cannot imagine more for the money than this unit. It is a shame that it was discontinued. If Bruce could sell the boards from his discontinued products, it would be a good additional source of revenue.

The Transcendent Phono Stage is quiet, musical, relaxed, dynamic, detailed and powerful.

It whispers, then shouts, and sometimes I get startled when the Orchestra jumps from Mezzo Piano, to Forte... in the movement of the conductor's baton.

Tympani (Kettle Drums) get their full body and weight, and if you gave them 15" woofers, they would sound absolutely thrilling.

My killer Kettle Drum recording is Mythodea - Vangelis.

If you can watch this concert, the musicians, orchestra and theme make for an unforgettable cup of Tea.

You just have to get the sountrack on Vinyl to use your Turntable, or just buy the DVD and sit back for a super show, from the master Vangelis.

From Vocals to Jazz, from Rock to Salsa, this Transcendent Phono Stage delivers the goods.

Bruce Rozenblit knocked this one clear out of the park, but nobody was in the bleachers.

Transcendent Sound has great products and some real innovation in an audio market that thrives on repeating stuff.

Transcendent Sound actually innovates, offering kit products that have value and features not found in the mainstream.

www.transcendentsound.com

Unfortunately I did not have a pair of Metal Snippers so the chassis got scratched up when I drillled and filed the hole for the barrier strip.

The Transcendent Phono Preamp elevates even the most mundane Cartridge into a real, palpable, analog presentation. This Phono Preamp breathes life, and plays with astounding musicality. These are out of production so when you can grab one of these on the used market, RUN... don't walk. This Phono Stage is simply the most outrageous out there.

ON THE ART OF D.I.Y. AUDIO

The art, of making your own amps at Home, is quite nuanced, and rewarding

it requires skills in the Mechanical, Electrical and Bravery departments

You need to challenge Yourself, and embrace failures.

Unlike Kits, making your own Amps, at Home

is how you really learn Electricity and Electronics.

My Dear Mother (RIP) would buy patterns at JC Penney

She would Sew Her own Dresses for Work, She looked amazing.

Mom was blessed with many Talents and Hobbies.

Out of the four Daughters, Mom was the Rebel and so am I

My comments are always out of left field, I insert new perspectives

and thrive to stand corrected, and often do and thank the person.

I inherited my Mothers gifts, Her sense of Humor and Her distaste for feeble minds.

If someone feeble approaches, I don't have to do anything.

Their feeble senses will repel Me, saving Me time, money and stress.

But those who are awake, somehow resonate with my inner light

They bask in the breeze of a cool conversation or topic.

In Jason Isbell's song "Elephant" one line really hits home.

"Surrounded by Her familiy I saw that She was dying alone"

I also have Family members, whom I have stood close to physically

but never Met. Some stare at me like some animal in a Zoo they

would rather avoid, and this is how the Spiritual 101 world operates.

THE B.S. FACTOR

When someone spoke to my Mom who was a bit off, exuded bad vibes

or was simply obnoxious, Mom would utter the word...

"Interesting"

In Mom's language, She was calling out

Mr. Paul Klipsch's BS lapel Pin

SO WHY TUBES?

So I get this question, most of the time, when the subject of Tubes

moves into a conversation, and the listener usually has a smirk when asking,

Why Tubes?

Well my answer is simple, Music, not sound effects.

No shaking walls

No rattling license plates.

No massive Subwoofers.

No cutting off Midrange

No boosting of Bass or Treble.

Maybe, just maybe a touch of Loudness

after all, Mr. Fletcher & Mr.Munson would agree.

Just..... Music, not sound effects

Tubes are Musical

Tubes are imperfect.

Tubes are from an age, when Recorded media was mostly Music.

When people started to discover new Musical genres through LP recordings.

Yet, some "Music" today.. is only entertainment, by entertainers, not Musicians.

Tubes are Music, borne of human innovation

Tubes are also fun to work with, you can build stuff yourself, at Home.

Tubes are historic, organic, an aspect of old traditional electronics.

Tubes are easy to work with, and they wear out, just like Us.

Creating Equipment with Tubes

No PC Boards required, just maybe a few here and there

after all it's 2024, not 1948.

Most DIY Tube Amps, are constructed from Natural, organic

Point-to-Point Wiring

Artisanal wiring techniques that are still empowering Tube equipment, today

with the construction techniques of yesterday.

Classic Tube Amps, to Me they transcend Time and Space.

But I am biased to mechanically and electrically sound connections.

Just cover your mechanically and electrically correct connections with Solder

Solder locks out corrosion that would affect the connection over time.

Solder is never Glue.... ever-never.

"God made only a few perfect Electrical connections

the rest, God covered with Solder"

Yes!

Solder it is not a "mechanical connection" or "an electrical glue"

This narrative, creates intermittency and future ghosting problems.

I have corrected the "touch a wire to a metal" many times over

the untrained use solder like a Welder would, like a Metal Glue.

A wire needs to be mechanically twisted and fastened to a clean surface.

Except for PC Boards where Wited/Leads are Tack Soldered through an Eyelet

(This is called a "solder bridge").

Note that PC Boards are "solder bridges" that degrade over time.

Tagboard Connecions, after 50 years, could also use a cleaning & solder re-flow.

I have solved a few Hammond Organ "sonic flu" with a Solder Re-flow.

The Organ just does not sound right, then BAM, the floodgates open.

Modern surface mount components

they use a special solder that is much better than 60/40

Even surface mount components are tack-soldered with pure heat

their contacts, eventually become resistive over time, inevitable.

PC board electronics are not designed to last forever.

Only maybe 10-15 years, if lucky 20-30 years.

When your old Plasma Flat Panel TV starts to act-up with Gremlins

Your CD Player might lose Panel Brightness, or that old trusty Laptop starts to act-up

a Cold Solder joint may be lurking inside of the appliance.

Sometimes Bean Counting Managers decide to derate components

and they eventually fail due to repeated overheating.

Cold Solder joints, are frequently to blame for lack of longevity, and some ghost faults.

Simple, but effective Point to Point Wiring lasts much longer

over 100 years longer.

Solder exists, to keep out the detrimental effects of moisture

Protect from Salt air and moisture exposure.

Solder, is the final protection cover

of an electrically and mechanically sound connection.

Solder protects against moisture, corrosion and time.

The true measure of a Master Tube Builder

Is for the Amp, to work, without a single drop of Solder.

Then, all the connections are covered-up, with Solder.

Yet most builders, like myself, solder we go for practical reasons of course.

I used a highlighter to mark off one-by-one the Solder Connections.

This is so as I do not miss one by mistake.

I am just making a point here, practical & factual.

Now back to Tubes from Solder

Yes Tubes can sound awful and also very, very good

Most of the time magical.

But they have to be operated at their proper Quiescent state.

Tubes are not always quiet, and as reliable and repeatable as Solid State.

But... Tubes are still available for online purchase

Unlike Solid State, that has proven to go quickly

"out of production"

The narrative still seems to linger on about Tubes:

"Can you still find Tubes"

"with a cynical smile?"

My response:

"Of course, far more than Solid State parts, that go out of production quicker than some Marriages"

This illustrates just how successful negative marketing has been

on the Human psyche.

Just try and order a red dot SONY NPN/PNP Transistor from 1973

GOOD LUCK, no hay.

You replace that component with an NTE/ECG generic

the Music will never perform the same.

Tubes are robust, tough

But can be also be fragile to "boosted" operating conditions

It is much harder to ruin Tube Equipment than Solid State when repairing.

With Solid State, a simple Oscilloscope probe slip, poof.

the death puff of smoke

 rises from the PC board Chip, Regulator, or Transistor

as the Music dies

A scorched Regulator, Chip, Diode, Transistor is an easy costly mistake

With Solid State Electronics

Are Tubes Different, heck yeah?

TUBE ROLLING

So all in all, Tubes can be "rolled and compared"

Tube circuits are simpler, require less parts.

Audio signals is less affected, by cumulative the "sonic imprints"

from the surrounding components, generally so.

Tubes use very high performing, much lower value Signal Capacitors that

do less damage to the delicate audio signals that we call Music.

Also lots of OEM parts are available today for Hobbyists when building with Tubes.

The list is long, yet I don't intend to cover all of the reasons why I enjoy Tube Amps.

My Website should be enough proof of how my Tube Hobby has enhanced my Life.

Tubes do wear out, and require replacement, this is one down side.

But when an out of production Solid State component dies

 an exact replacement is usually unavailable.

Sometimes due to lack of production.

But mostly due to Tax Laws on Inventory

and the dwindling parts stores we used to have as our

Society shifts from actually being somewhere physically

to an Online paradign. Just like old parts can fail

We are today an approximation, with an online existence.

Substiture Solid State parts may result in degraded performance

This is the detriment of the price we pay for

Generic Solid State replacement parts.

But how much longer does ECG and NTE have? Not much...

People pay good money for real Burr-Brown OP Amps, and for a reason, Music.

Ask any Electric Guitar player if they want a Tube Amp?

Yet I cannot see how Tube Amps will survive when Amp modeling

is just as close to the real thing. But the tragic truth is evident.

The majority of people don't care to feed their ears well.

About Tubes and Bass Amplification

Electric Bass players, umm, my humble opinion with Electric Bass

is where Solid State makes the electric Bass Guitar sound best

(Tube heresy?, naaah, just a reality as we pluck 40.1 Hz)

My Tube vs. Solid State short list

For Music, Musical Instruments, and Human Vocals; TUBES.

If you need to make your ears bleed, SOLID STATE.

If you need Jurassic Park or Cars Low Frequency thrills, SOLID STATE.

If you obsess over Power Supply ripple and slight buzzing; SOLID STATE.

If you want instant gratification; SOLID STATE.

If you want super low noise and high specifications; SOLID STATE.

If you seek convenience and ease of ownership; SOLID STATE.

If you are obsessive/compulsive to minute buzzing sounds; STAY AWAY FROM TUBES.

Tubes cannot easily out spec Solid State in Damping factor.

SOLID STATE is the Damping Factor Dictator.

ARE PEOPLE IMPRESSED?

Can you make bleeding ears & impress audiences with Tubes?

Typically NOT... people are in too much of a HURRY these days...

Addicted to Bass & Sugar

People don't have any time or patience, or interest to sit down

to discover NOS Music like Bill Evans, Ralph Towner or Jean-Luc Ponty

How many people have heard of Gene Krupa, Max Roach, or Peter Green?

As Tubes are not show offs, or brazenly LOUD devices.

Making Tubes brash and loud, at home, gets expensive...


I consider High Powered Tube amps to be in a separate class.

These are the kind of Tube Amps that offer 100 Watts per channel or more.

Most commercially available Tube Amps top out at 60 Watts

Some 80 Watts per channel but rare indeed.

More than 80 Watts, you need a "deep wallet".

If you have very difficult inefficient loudspeakers

a 200 Watt Tube Amp may work.

200 Tube Watts will definitely move Low efficiency Speakers

How well... until you try, you will not know.

I heard 200 Watts at the Capital Audio Festival

And I will put some Videos to post here of my visit to the Jolida Room.

Capital Audio Festival and Rocky Mountain Audio Festival I have Hi8 Video.

Power and Headroom

Are needed, so that Music does not sound harsh when cranked-up

especially with Mid to Low efficiency speakers.

High damping factors help Woofers rapidly recover from transients.

And these types of high quality speakers cost a Home Down Payment.

Also, Tubes love certain companion speakers, so they are finicky in this regard...

This would make for an interesting

Tinder for Tube Amps

Looking for an 85dB Transmission line, with sweet tweeters and large woofers.

An E-Harmony or OurTime for Tube Amps seeking ideal Speaker companions.

Still curious about building a 60W or less powered DIY Tube Amplifier?

Be my guest, and enjoy the journey and my stories.

Since 1996 when I made my Mullard 5-20's sound

I have now logged over 23 years of DIY work and close

to 50 years of Audio Systems enjoyment, and 45 years of collecting LP's.

My Engineering Career spans 39 amazing years.

Twinkle Twinkle Little Star, V = IR.

Tubes: are for Music, not Sound Effects

Kicking off a Tube Amp build from Scratch?

These are the basic elements required

Purpose-built workbench

Proper lighting

 Proper tools

 Test equipment

Safe and abundant work/storage space

 Good lighting

Don't confuse a simple folding table, with a proper Workbench.

One false kick of the leg, there goes your Hobby

to the floor, I know, as I have been there.

The do-it-yourself 'DIY' - Caveats

Some boomers easily recall those days when Electronic Kits were commonplace

Heathkit, Scott Kits, Dynaco, EICO, etc. and saved money.

What most forgot, were the well meaning people, who spent good money

but could not solder, or follow/interpret or understand step-by-step instructions

Manual skills lacking, they may have tried to build a Kit and failed.

Sometimes, they never were able to fix a failed kit attempt.

Then put it away in frustration, or sold it off for parts.

The problem with building a Kit Amp, you have to follow instructions meticulously

if you do not understand electronics, else you will fail.

People who do not know why a connection is being made, need to use a highlighter to

mark each and every small step in the instructions. Just one careless deviation and

you will have created a problem that will be complicated to find.

So make sure, that you are perfectly clear, in this reality.

Yes I have built a few kits, and they are awesome time savers.

Kits are time savers as they give you a head start, saving labor and special tools.

Rest assured that a Kit, is a better path for first timers than D.I.Y.

Unless one plans to build many amps, a Kit is the best way forward.

Why spend thousands on tools you will only use sparingly.

Also I read on DIY Kit Forums people who have created wiring errors.

They struggle to get help from the Sellers, and the other Forum Members

cannot help from poorly taken Photos.

Avoid this, buy Tube Amps already built.

Be honest with yourself. If you have two left thumbs

Have never held a Soldering Iron or know

what a Resistor does and how it works.

Buy an already built Tube Amp....

A great YouTUBE channel

I really enjoy, and also learn from

https://www.youtube.com/@SkunkieDesignsElectronics

Sit back, relax and get nothing but the truth

Great tips for the improvement of bad construction techniques,

Also awesome DIY amplifiers.

She is the epitomy of pragmatism and electronics

Smart Lady, and very skilled.

SOME ONLINE KITS FOR THE BRAVE

Mr. Bob Latino is a Subject Matter Expert with decades of experience

only the finest kits available.

http://www.tubes4hifi.com/ST70.htm

This link opens the door to the Dynaco heyday of the 60's.

https://www.dynakitparts.com/?

US Patent holder Bruce Rozenblit offers superior sound at a great price.

The purity and air of an OTL Tube Amplifier is worth exploring.

The challenge is getting a Subwoofer that can keep up with an OTL Amplifier.

https://www.transcendentsound.com/products-.html

I have been ordering from Triode Electronics since the 90's.

http://www.triodeelectronics.com/hifikits.html

These products are fine hand crafted instruments, you are literally along for the ride when listening.

Seatbelts suggested in a quiet zone.

https://bottlehead.com/bottlehead-products/

Fine Japanese Kits and Products, high quality and true craftsmanship

https://www.elekit.co.jp/en/product/?type=category&q=Amplifier+kits

More fine kits to build with Musical Instrument and Hi-Fidelity Kits

https://www.tubedepot.com/t/diy-central/kits-tube-amp

 

TIME, IS THE CURRENCY OF THE WISE

EACH MOMENT IN LIFE, ONLY HAPPENS ONCE

WE LIVE THIS GIFT EVERY DAY, BUT DIE ONCE, SOME TWICE

MEDICARE AND SOCIAL SECURITY

FOR SOME MAYBE?

 

EARLY CONCEPTUAL DRAWING OF WHAT BECAME THE

NeoClassic30

THE FIRST DIY GUITAR AMPLIFIER HEAD IN MY

HAND MADE AMPLIFIER PORTFOLIO

SO THE STORY GOES SOMETHING LIKE THIS.....

Hobbies and also Professions often experience 'crossover' moments

Artists can 'crossover' to a different audience/genre/language.

This was my Tube Amp crossover build.

Since 1996 building Hi-Fi amps, in 2021 my first Tube Guitar amplifier

Although I was already building Heathkits back in 1979.

I departed my comfort zone, to explore the "Musical Instrument" genre of Tube Amplifiers

YES ALL TUBE from the Rectifier to the 12AX7 Preamp/Tone Control

Not even one Silicon Diode, all tube, all TONE.

This Amp implements the Olson Amplifier using "weird but cool" classic Tubes of yesterday.

Imagine using the 6J5 & 6F6 that were very popular in the 40's and 50's, now on a new amp, unheard of.

My motivation for the NeoClassic 30 started, in conversations with my Guitar Mentor and good Friend.

The Story behind the NeoClassic30...

I started a new position at Codan Communications, amazing product the MT-4E

it is a design built in the old way, completely free of planned obsolescence.

I wish more companies would have Noble people creating designs that last decades.

I DIGRESS.....

At Codan I collaborated with superbly wonderful people;

Ben P., Paul M., Caitlin J., Sara E., Andrea, Wayne F., John M., Rick L. and Mark M.

Among these great people was my Yoda

Clif

(thats Clif, with one F not 2, you flunkies)

Clif planted the creational seed of the NeoClassic30

A great Guitarist, Clif and I spoke about Tube Amps, related subjects.

After years of neglecting my three Guitars

playing the same 5 songs from High School/College

I was stuck in a Guitar rut

Common for many amateur Guitar players who don't practice.

But even worse

I was facing the Sad loss of my once High School/College

Campfire Guitar skills

Reality whispered into my ears

"You suck"

So one evening, by invitation

I carried my old 1974 Giannini Student Acoustic Guitar

to visit my "soon to be" Guitar mentor.

We played a few tunes, and I realized that there still might be hope.

Soon after that, we began to play, as often as we could together

in His basement.

My Tube Amp hobby, became part of our conversation.

In these talks, I imagined a Tube Amp Guitar project

for Clif, that became very real

whose results of my vision are evident below.

It took me close to one Year to draw, think, order and accumulate parts

the results are proof that I can build a nice "Tube Amplifier Head"

Learning how to make stuff from Concept to Final Testing is a skill that I

honed for over 20 years of bench time

metal hole punches, metal reamers, metal nibblers, cuts, burns...

Tube Sockets, Switches

and all kind of Frankenstein experiments

that taught me how to make a dream reality....

And also what does not work out...

On the subject of Dreams

DREAMS, TO ME ARE INPUTS FOR FUTURE ACCOMPLISHMENTS

BLOOD, SWEAT & TEARS MATERIALZE DREAMS

ALSO DREAMS REMAIN DREAMS UNTIL WE MAKE THEM HAPPEN IN REAL LIFE

UNLESS DREAMS ARE FORCED OUT OF THE IMAGINATION INTO REALITY

THEY REMAIN DREAMS IN A GARDEN OF STATIC IDEAS AND SOME SENSE OF HOPE

MAKE YOUR DREAMS COME TRUE

FEED YOUR BODY WELL,

TAKE CARE OF YOUR HEALTH,

MANAGE YOUR STRESS AND ANXIETY,

WALK MILES EVERY WEEK,

GET SUN ON YOUR SKIN,

SEEK HELP AND ADVICE

REMEMBER ALWAYS, QUALITY OVER QUANTITY

BETTER TO WALK 1 MILE AT A GOOD PACE

THAN JUST LIMP ALONG.

The "NeoClassic30" 6F6 - Triode

Cathode Bias, clear as a Bell

 The NeoClassic 30

A musical instrument amplifier - for general M.I. amplification

Proven with both Guitar and Bass

Road Tested, capable of delivering consistent performance

The Neo30 is about going back to the basics

Clean retro look with simple controls

No thumps, no Hum, pure artisanal P.T.P. wiring

Hand Crafted, and most important 100% Tube

DOES THE NEO30 SOUND COOL?

I would say different... than the usual 10-15 Watt all Tube Amp Head

First off, the Tube lineup is "a-typical" think old style retro

Honestly I really have not heard this amp much myself

as Clif fetched it as soon as it was built and sounding.

Clif began using it daily, loving the sound as I got reports back on a regular basis.

The little that I heard, places this amp into a CLEAN and LEAN sound.

Usually, Guitar Amps are Pentode Connected, this Neo30 is Triode, iconoclastic Push Pull

Most Guitar Amps are Fixed Bias, the Neo is Cathode Bias.

What it lacks in Crunch it makes up for in Tone & Clarity.

Just ignore YouTube videos that claim Tube Amps don't have Tone....

The 6F6S, Triode Strapped w/100 Ohm Metal Film Resistors phenomenal...

Push-pull 4x6F6S Tubes, in a 2+2 Dual Triode configuration.

Output Transformer is a super high quality Hammond Fender replacement.

A Hammond 1750JA that offers 4 or 8 Ohms, impeccable Hammond sound

There are a few more tricks I can do to make my next amp design more exciting.

Maybe "Variable Feedback" Control plus a "Bass Boost" with SPST switch

to maybe replace the Loudness Control with a single SPST Switch..... ?

So many different things to try.... my friend picked this up so I did not have

my usual soak and tweak period.

Neo30 Features/Characteristics:

Studio & Road "Compact" Tube Amplifier Head

Dual Push-Pull 6F6 Power Tubes, Triode Mode

(Future versions will have 6V6, EL80/6227, 6AQ5 variants)

Pure - Cathode Bias Amplifier Platform

Requires Matched Power Tubes

Universal AC Transformer 100vac, 120vac, 240vac, 50/60 Hz

Works in any country, the primary can be wired according to the mains standard

Hammond 1750JA Fender "Hot Rod Deluxe" Output Transformer

Hammond Filtering Choke

JJ Electrolytic Capacitors - Low Impedance & ESR

Hammond Chassis & Ventilated protective cover

"Locking" 4 and 8 Ohm Speaker Jacks

Premium PURETONE Nickel Input Jack

2 Amp Slo Blo Fuse & Internal Spare Fuse

Power Tubes - 6F6S Pentode x 4 (6V6GT version in the plan for 2022)

Phase Splitter - 6SN7GT x 1

Driver Tube - 6J5 Triode x 1

Tone Control Triode - 12AX7A (½)

Gain Stage Triode - 12AX7A (½)

Tube Rectifier - Sovtek 5Y3GT (150ma rated*) x 1

*Use of NOS 5Y3 requires VARIAC set to 117 VAC on AC line voltage

LIVE FROM A GUITAR SESSION WITH MY 2x12 EBay PROJECT

ABOUT THE "EBAY" PINE SPEAKER CABINET

PRE-NEO SIDE PROJECT

DUAL JENSEN P12R-16 2x12" ALNICO

Before the NeoClassic30 I had a pair of leftover Jensen Alnico 12" Guitar Speakers

These were from my Pilot PSV-2 Woofer problem.

I was eventually able to buy a single PSV-2 speaker for a spare Woofer

 and now the PSV-2 are 100% they both have original 16 Ohm Drivers

intact, they sound terrific and have been gifted to my Cousin Ed.

So with the awesome Jensen speakers leftover what else but a 2x12

 I decided my Guitar Instructor Clif could use an Alnico Cabinet

and also for his pocket sized ORANGE Micro Amplifier..... great for traveling light

This EBay Cabinet became Dual 12" Vertical stuffed with Jensen Alnico Drivers!!!

The Drivers were barely used....

These drivers have an incredibly saturated midrange capability.

it really helps the Electric Guitar ring like a Bell and Clean Bites, like a Barracuda

This 2x12 allows sounds quite unlike a traditional Guitar Amp 2x12 due to the clarity

of the drivers, even though the NeoClassic30 Tubes are being operated at 75% of Max.

I decided to operate the 6F6S a bit Hotter than my HiFi Stereo version AURORA.

With rational Power Headroom, you can enable and create a Musical Garden of sound.

I can hear the difference between a Tube that is pushed close to or past the limits.

Designing for Tube Life is one of my favorite asks..... the results are always

the same, early breakup with plenty of rich overtones and grit.

It sure does have a nice bite to it when pushed!!!

Great Head for Guitar Solo's, Vocals and also Acoustic Instruments.

The NeoClassic30 came later, and proved to be a match for this 2x12 Alnico Speaker

NeoClassic 30 after the Front Panel arrived

 Amplifier Update on 7/3/21:

Amp in service from March, and a few tweaks were necessary...

Changed Loudness Capacitor, 0.0022uF to 0.01uF, Loudness now musically textured, lush & present

Adds more body to the lower registers, Loudness is perfectly controlled at full setting, no distortion

THE ACTUAL BUILD

of the NeoClassic30

CONSTRUCTION KICKOFF JANUARY 2021 - CHILLY AND SUNNY DAY

Here are some photos during the construction, my lovely wife is the coolest, she just cheered me on and kept me sane during the build

I simply invaded Her kitchen space, She was so, so patient and cooperative, and when parts fell on the floor, there She came to the rescue

As always, build time calls for Coffee, Tea, Juice or Water Bottles, Beer and Wine after the soldering iron is OFF and I am done for the day.

The metalwork kickoff day was a full out assault of my Wife's Kitchen Table area,

my garage shop bench was January cold.. brrrrr.

 Always have "Band-Aids" and "Neosporin", I always cut myself on the sharp metal edges.

Every Amp I have made, draws a few drops of my blood, must be a Spiritual blessing

Before drilling the first hole, month's of planning and deciding how the topology fits is needed.

I just did not order parts, the process of creating a amplifier from scratch is slow and deliberately tedious.

A bit more progress, the tubes are now set in their places, this lineup took me a few month's to figure out

I made at least 10 different combinations of how to mount the parts on the chassis

Note from the photo above that the front panel control positions come later in the build

Their final locations on the front panel are a result of the internal wiring progress

One note from my build, once you have many potentiometers on a panel, the wiring becomes critical to eliminating hum

IT'S ALIVE, MARCH 2021

Here we have the morning after Power was applied & my Guitar connected, YES I GOT MUSIC plus A SUPER HUGE GRIN

I was speechless, my Wife shot a video, dumbfounded it worked and as well as it did, I was not expecting such bliss.

The Front Panel design.

Just download the SW & design your own panels

Then upload the design file, it is that simple, the tedious part consists of all

the Caliper measurements, you need a Caliper

The panel arrived in less that 10 days

Awesome quality, a professional finish

https://www.frontpanelexpress.com/

SO WHAT IS MY NEXT GUITAR AMP PROJECT?

I am currently scheming on my next Guitar Tube Head

Design targets;

5 Watts Push Pull Triode, lower power.

Adjustable Cathode Bias or Fixed Bias

Smaller than the NeoClassic30 as small as I can build it!

Compact as possible......

Call it the NeoClassic10

Thinking about the next smaller Hammond Chassis...

Pondering Power Tubes Pair.....

Looking at 6V6, 6AQ5, E80L/6227, EL84/6BQ5

I want to add an effect loop as well....

More to follow in 2023.

HOW ABOUT A BASS GUITAR TUBE AMP?

I am also scheming a Bass Guitar Tube Head

Design targets;

50 Watts using Magnetek-Triad S42A Output Transformer (from my private stash)

Fixed Bias so that the Tubes can be adjusted

Adjustable AC Balance for Lowest Distortion...

Compact as possible......

Call it the Bass50

The Power Tubes .....

 Got to be 6L6 or 6550 ....

More to follow in late 2023/2024

THE HEART OF ANY TUBE AMPLIFIER

THE UN-REGULATED POWER SUPPLY

"THE ENGINE ROOM BLOCK DIAGRAM"

A typical "Un-Regulated" Tube Amp DC Supply Schematic

The Blue Box can be a Rectifier Tube or (2) Diodes

If the Plate Transformer does not have a Center Tap

You then need to use a Bridge Rectifier and this is

99% of the time Diodes. Although one can make a Bridge

Rectifier with Tubes, it is not a desirable effort.

You must learn how to explain the Block Diagram schematic above, and how it works

When you do, and you look at your Neighborhood Power Poles

and see the Cans hanging on the Poles... a light will go on in your head.

When you look at your Home Breaker Panel, You will understand it.

By golly, those are Utility Step-Down Transformers, now I can explain what

the difference is between and Step Up (Plate for Tubes Transformer)

and a Step Down (Filament Transformer).

When you look at your Home Breaker Panel, bingo!

That one is a Step Down to 240VAC with a Ground Rod on the Center Tap.

You measure 120VAC between the Neutral and L1/L2 Hot Lines.

Between L1 and L2 you measure 240VAC.

You will know then what Split-Phase Balanced Power is

and how to evenly distribute Circuit Breakers when you Wire a new Home.

Many more cool things come, when we have Hobbies we love and learn

about the Homes we pay mortgages for. After all, you are paying good money for your House

so it is to your benefit to learn how it works? Same goes for your Car, Boat, Motorcycle, Bicycle, Plane, etc.

I got a STEM Degree 1986 and what I learned changed my life forever.

Pull away from those Apps that make you think you are Smart.

Then break out the wires and meters, it's time to ROCK.

NOW, BACK TO THE UN-REGULATED TUBE AMP POWER SUPPLY

 Power Supplies are the Engine Room of any Tube Amplifier or Preamplifier project

Every aspect of the circuit above, is key to best overall success of your DIY Amplifier

Yes I have made my 30+ years of mistakes, so you don't have to.

From the rectified High Voltage DC, to the proper AC Filament Loading, it all converges

A multi-section Plate and Filament Transformer is not a static device.

Each secondary winding section loads the Transformer primary, thus there is a total load

If you do not load all of the secondary sections, the resulting voltages will be different than when you do.

Transformer AC voltages and currents are empirically determined by testing and simulating, of course respecting Max values.

But what you need to look at are the F.L and N.L. voltages

F.L - Full Load, N.L. - No Load

For an unknown transformer you can use a 60 Hz AC signal generator on the primary and measure the AC Voltages on all of the sections

including the primary section, and calculate the voltages using Transformer Mathematics.

As far as their respective Current Capacities, that requires empirical load testing and this can get expensive to have

the proper loading resistors to plot the Load Curve of each Transformer Secondary section.

What I am saying here is the difficult specification to determine if you lack the transformer datasheet is

the Current capacity of the Transformer Secondary's as this

is not something you can easily calculate, you would need to disassemble the Transformer and

reverse Engineer (unwind) and note down the number of Turns, the Geometry of the Core and the gauge

of each wire to calculate the Current capacities, so when this specification is missing

the only way to estimate is empirically by loading the Transformer and plotting a loading curve for each

section on the Secondary simultaneously, a tough job for even the best equipped workbench.

Manufacturers sometimes print this data on the Transformer Case with a Label, but

when you purchase a Tube Amp, this information is often eliminated so the products

holds secret sauces and the "copycats" cannot clone the products.

Makes sense for intellectual property.

The other way to determine the loading is to connect DC supply to each part of the Tube Amp

with the correct DC voltage and measure the current draw, then work in reverse to calculate the

necessary AC Transformer Secondary Voltage and Current, again no easy task.

All of these measurements must be done in "Steady State Operation".

So..... back to the Power Supply topic from a 1000 ft. level.

Every single Amplifier or Preamplifier I have built from scratch

always starts with the Power Supply.

You model the Power Supply first, then the rest of the project.

Below is my Power Supply Simulator, I built around 1998

0-500 VDC, 0-150ma DC or 0-500ma by swapping out the DC Ammeters

I sanded the hole on the 1x3 to perfectly fit the Shurite Meters, silky smooth.

(Explanation on how It works - is Under Construction)

HERE IS A USEFUL JIG

MY DIY TUBE POWER SUPPLY SIMULATOR

Here I load, test & measure Plate/Filament Transformers

Before I drill any holes on any chassis

 High Voltage -  DC Voltage Load "Sag"

 High Voltage - DC Total Current Load

5V or 6V Rectifier Tube AC Filament Loading

(High Power Load Resistors simulate 6.3 VAC Filament Loads separately)

Important Design Note:

To get the correct loading, you have to load all of the Transformer Secondary Sections, not just one.

 

 

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