Tube Amp Spa
THIS IS THE SHERMAN WATERING HOLE
WHERE TECHNICAL AUDIO LOVERS JUST HANG OUT
AND READ ABOUT COOL STUFF RELATED TO ME
MY HOBBY AND MY LEGACY YEARS
BUILT ON CUTS, SWEAT & A FEW SHOCKS
IT GOES SOMETHING LIKE THIS
MY MEMORY, AS MUCH AS I CAN MAKE IT PRODUCE
In the late 80's to the early 2000's,
I must confess,
I was subscribed to both Stereophile & The Absolute Sound.
Now, I am just a Jazziz subscriber, and own a remarkable
Jazziz CD Collection with wonderful new artists
that often Shazam, has no clue about, Nice!
AI is powerful, until it cannot even produce
an Output for a totally unknown Input.
If AI does not have it in their database, AI will be clueless.
The algorithms needed for AI to calculate a prediction of
what it is processing may eventually be a reality.
But we are A LONG ROAD away from that.
Bob Marley would have sang:
"Don't you fear AI technology, for none of them can stop the Time"
I read these Audio Magazines, cover to cover
with a Tea/Beer/Wine Light Classical Music
Audio publications, taught about who were the Masters who made
today's Audio Scene possible.
I honor here a few of the visionaries by their names;
David Hafler
Ed Laurent
Stan Warren
Nelson Pass
Saul Marantz
Walt Jung
Sidney Harman
Bernard Kardon
Avery Fisher
H.H. Scott
Stuart Hegeman, and many, many more...
THE END OF THE DYNACO AGE
In the 1980's
Dynaco, by then PANOR CORP
and Panor
had just re-released the Stereo 70 in the Late 90's
and a Version II in 2004, to mixed reviews.
Probably using the wrong Speakers for the review (just my hunch).
Still, these Dynaco Tube amps were $995-1100 or more, even back then "Ouch"
I was a young Engineer making mid 50's and
that was a chunk of Cash,
I just did not
have to spend off on a luxury.
AUDIO MAGAZINE HEROES
My heroes in Audio publications in my early Audio journey.
Most of these amazing people, are already with Harvey listening
to some 300H Tubes (H = Heaven).
J. Gordon-Holt
Corey Greenberg
Harvey Rosenberg
Harry Pearson
Charlie Kittleson
and a few more....
MY FIRST SERIOUS AUDIO PURCHASE
My Wife and I drove to Roanoke VA
as we were invited to a Klipsch Factory presentation
of the Klipsch Sub-Sat System. Back in 1991 Home Theater was in full Bloom back then.
I did finance an ADCOM GTP-400/GFA-535
at Audiotronics. That evening I drove Home to Lynchburg
with two Boxes of Goodies
and a loan from AVCO, that was paid in less than 1 year.
That Credit allowed me to borrow more later for an Emergency. I learned
that
Good Credit is important for recent College Graduates.
ADCOM was at that time, the HOT Stereophile Class D brand.
It was entry level Hi-Fi, for budget conscious Music lovers.
Cary Audio ads were the Beverly Hills of Audio, as still is McIntosh.
The Cary Audio Lady, listening in bliss, to
DHT TUBES, what?
Eventually, I would order a copy of "The Mullard Book"
and the seeds that sprouted into ShermanAudio were planted.
EL-34 Push Pull plots of Output Impedance, Power vs. Frequency Response
It was incredible information for an Me as an EE.
I now fully understood how a Tube Push Pull amplifier
Output Transformer section works.
I never took Tubes in College, they were already obsolete.
Tubes are "Non-Complementary" no NPN/PNP with Tubes.
I read about optimizing EL-34's
creating clean Power, through an Output Transformer.
A pair of Mullard EL-34's provided 20W of Peak Power.
I noticed the EF86, a midget Pentode?
The EF86 taught me to be careful with Tube Substitution Books.
The EF86 was listed as an EL-84 sub, hence I made
my First Monoblocks with EL-84 in the input, worked, but sounded
BOLD, BRASH, OVER THE TOP
Learning and Education are hard things, but the energy is worth it.
This Mullard 5-20 amp was
"Low distortion" for 1959.
So,
I decided to create my own Mullard 5-20 Monoblocks from parts.
The Mullard book presented the 5-20 and all of their designs like
Engineers, for Engineers. I am always accused of talking too
much detail, of being over the top when I answer questions.
Well I do not just answer questions, I inform and educate.
A skill that I use in Public Speaking with a high degree of success.
WHEN DID THE MULLARD'S FIRST SOUND?
This started back in Mid 1996.
They 5-20's first sounded in the Summer of '96 at 3am.
I had about 5 Miller Light's on me and when I threw the switch
I finally got music with no motor-boating.
Music that made my heart skip a
beat and my Hairs stand up, goosebumps.
No recent experience can surpass the Joy of hearing your FIRST AMP
sound.
I remember going back to the bedroom at 4am and
whispering to my wife
THEY WORKED
It was Spring of 96 and I was already infested with Tube Audio.
Now these 5-20 Amps, took 25 years to debug and perfect, no joke.
The Mullard 5-20's are not an easy build, for non-intuitive reasons.
And following the specs for the Power Transformer and Choke in the Manual
taught me a serious lesson, they just were not relevant 60 years later.
The Mains Transformer was specified as 400-0-400 Volts, a huge mistake
when using modern, Lower Iron and Copper Loss Hammond Transformers.
The correct Hammond is in my Website and has 115/125V AC Switching.
Today's Mains transformers are more efficient and wound to tighter tolerances.
Hence they will perform the Vintage Mains types.
But... old Output Transformers, it is here where modern types
might not sound as good. They may measure better, but the music seems
to lose some air, they do not breathe like a Freed, Fisher, Scott,
Knight...
So in the Mullard Book, the level of Rectified DC Voltage was sheer suicide for the EL34's.
Aggravated by a 115V Primary, I struggled to understand while
my EL-34 Red Plates
screamed and died and early $death$, so did my bank account.
Note that
5-20's are Plate Voltage sensitive
as are most Cathode
Biased Power Amps.
After many Red Plates, and Worn Quads of premium EL-34's
I finally perfected these Amplifiers in 2018-2019 in Ashburm VA.
The 5-20's are very nice, especially with a quiet Preamp.
The 5-20's are dead quiet now and Musical.
What they lack in inner detail, they have in midrange bloom.
It has to be partly the EL-34 sound, each Pentode can do
some things well, and the EL-34 is a Midrange King.
I would state the 5-20's Sound is clear, unlike what tubes do.
Fast, Present and Harmonically Rich, but never bloated in the Bass.
I have all of the parts defined now, so if You decide to build
a pair of 5-20's, so You can avoid all of My pitfalls with
none of the hassles I faced, I suffered the build so You don't have to.
The full 5-20 story is in my Website.
For every
Amp, Preamp, Speaker and Test Jig I have created
a story unfolds in my Journey and Logs, here are those stories.
Sit back and enjoy the electrons flowing inside of
a Glass Vacuum.
TUBE NIRVANA?
Ultimately, my final destination is Tube Nirvana so BTW
I have been close, but not YET arrived.
I think my closest to Nirvana, was a pair of
Jolida 211 - 200 Watt/Ch Monoblocks
A pair of Omnidirectional MB-Quart Speakers.
I was in the lobby of Tube Heaven, but the door was still locked.
This happened at the
Capital Audio Fest, Sheraton - Silver Spring MD.
Sometime back in 2011 maybe? I have to check my Video Camera.
Now that was knocking on Heaven's door
I took a video of this, so will post here soon.
A DIY TUBE HOBBY IS NOT AN EASY STREET
IT IS THE HOOD OF AUDIO.
AS ALL GOOD THINGS IN LIFE ARE NOT EASY.
THE COSTS HAVE NOW TRIPLED FROM THE 90'S
AND LOTS OF WHAT WAS ONCE AVAILABLE IS
NOW OUT OF PRODUCTION, EXCEPT THE TUBES
THESE ARE STILL ORDERABLE.
GETTING PARTS
IT TAKES MORE EFFORT NOW TO HUNT FOR PARTS
THAN TO BUY FOREIGN CHINESE TUBE AMPS
EBAY IS STILL AWESOME
BUT GREEDY PEOPLE SELL THEIR GREED, NOT ITEMS.
AND THE FREE SHIPPING THAT CHINA GETS,
TO SEND US STUFF, MAKES CHINA THE GO-TO FOR PARTS
AMAZON IS NOT FAR BEHIND EITHER, THEY DELIVER!
IF YOU EVER ASKED YOURSELF, WHY IT COSTS MORE
TO MAIL A PACKAGE TO THE NEXT U.S. TOWN,
WHILE A LARGE BOX FROM BEIJING COSTS THE SENDER CLOSE TO NOTHING
THANK THE INTERNATIONAL POSTAL UNION AND OUR
TAX DOLLARS, AS WE ARE NOT ONLY PAYING FOR THIS,
WE ALSO PAY FOR WARS, NATO, ETC. "UNITED WE FUND" IS OUR NEW MOTTO.
THIS ARTICLE EXPLAINS THE CHINA ADVANTAGE
AS A SUPPOSED 'TRANSITIONAL COUNTRY'
TRANSITION TO WHERE? TAIWAN?
https://www.scmp.com/news/china/diplomacy/article/2169144/chinas-cheap-shipping-advantage-explained
MY
TROUBLESHOOTING TIPS
On "Close Encounters" of the "Humming" kind
HOW TO DIAGNOSE THE UBIQUITOUS "UN-MOLESTED" CLASSIC EBay TUBE AMP
AND WHY USING 60 YEAR OLD TUBE AMPS IN 100% ORIGINAL STATE IS DOGMATICALLY
FOOLISH
YES YOU CAN ASSEMBLE A CURRENT LIMITER
OR MAYBE ACQUIRE A USEFUL VARIAC
PLEASE DON'T JUST PLUG THAT OLD EBAY AMP INTO THE WALL
HOPE AND AUDIO DOGMA ARE NOT SAFETY PROTOCOLS
ONE RISKS BLOWING UP SOMETHING OF IRREPLACEABLE VALUE
FACTORY ORIGINAL OUTPUT TRANSFORMERS ARE "TREASURES"
YOU NEED TO PRESERVE AND PROTECT THEM
LOSING A POWER TRANSFORMER, THAT CAN BE REPLACED OR RE-WOUND
BUT FACTORY ORIGINAL OUTPUT TRANSFORMERS CANNOT!
YES OUTPUT TRANSFORMEFRS CAN BE RE-WOUND
BUT YOU CANNOT DUPLICATE THE ORIGINAL WIND
WINDING TECHNIQUES ARE NOW ALMOST TOTALY LOST IN TIME
AND THE SOUND OF A TUBE AMP IS DEFINED BY THE OUTPUT TRANSFORMERS
NOT THE TUBES, IMAGINE WHAT YOU MAY.
ROLLING POWER TUBES IS 20% OF THE TUBE AMP CHARACTER
THE REST IS IN THE OUTPUT TRANSFORMERS
LAMP CURRENT LIMITER
(BUY SPARE 75 TO 100 WATT INCANDESCENT BULBS, BEFORE THE GOVERNMENT BANS THEM)
STEP1: MEASURE AND TEST ALL TUBES,
REPLACE WITH GOOD TUBES, THIS IS CRITICAL TO START WITH GOOD TUBES. IF YOU DON'T
OWN A TUBE TESTER THEN CONSIDER RETURNING TO SOLID STATE, NO HARD FEELINGS, JUST
THE TRUTH.
STEP2: REPLACE FUSE WITH CORRECT
VALUE, THIS IS CRITICAL ALSO. USUALLY YOU WILL FIND THE WRONG FUSE OR A BYPASS.
STEP3: REPLACE ALL ELECTROLYTIC
CAPACITORS WITH FRESH NEW STOCK. FORGET
TALES OF REFORMING CAPACITORS, REFORMING OLD ELECTROLYTICS IS LIKE REFORMING CAREER
CRIMINALS, THEY JUST DON'T REFORM.
STEP4: MEASURE/REPLACE ALL OUT OF
TOLERANCE VOLTAGE DROPPING RESISTORS
IN THE POWER SUPPLY. JUST AS WELL REPLACE ALL CATHODE, GRID AND PLATE RESISTORS
WITH FRESH 2% TYPES, DON'T BE CHEAP, SPEND THE $15-20 DOLLARS
STEP5: REPLACE SIGNAL COUPLING
CAPACITORS WITH FRESH NEW CAPS, DON'T RISK LEAKY CAPACITORS, ORANGE DROPS
ARE FINE.
COUPLING CAPS, CAN DESTROY NEW TUBES IN A FEW WEEKS/MONTHS. THOSE 50+ YEAR OLD
CAPACITORS
AND CARBON COMP RESISTORS ARE BEYOND USEFUL SERVICE LIFE.
BREATHE NEW LIFE INTO OLD TUBE AMPS
DON'T ACCEPT THE MUFFLED, ROLLED-OFF, FUZZY
SOUND PEOPLE ASSOCIATE WITH TUBES.
BRAND NEW POTENTIOMETERS ALDO MAKE A DRAMATIC DIFFERENCE, AND ONE WOULD NEVER
KNOW.....
WOULD YOU KEEP YOUR 20 YEAR OLD SHOCK ABSORBERS, SO YOUR CAR WOULD REMAIN
"ALL ORIGINAL"?
STEP6: CONNECT TO A PAIR OF CHEAP SPEAKERS,
IMPORTANT SO YOU CAN TURN OFF THE POWER IF THE AMP MAKES WEIRD NOISES
STEP7: CONNECT
A RELIABLE SOURCE TO THE INPUT, THEN SET THE VOLUME AT ZERO AND ALL AMP CONTROLS TO
CENTER POSITIONS
STEP8: POWER
ON AMP - PRESS PLAY ON YOUR SOURCE - THEN AFTER 5 TO 8 SECONDS, START TO SLOWLY INCREASE
AMP/SOURCE VOLUME, IF AMP PLAYS WITH NO HUM/NOISES
GREAT.....
LEAVE IT ON FOR A BIT AND LOOK FOR ANY RED PLATES, SMELLS, ETC.
IF
YOUR AMP HUMS, POWER OFF. TIME TO TROUBLESHOOT THE HUM. IF IT SOUNDS LIKE A BUZZ
ITS 120HZ HUM
IF IT SOUNDS LIKE THE WORLD IS ENDING THAT IS 60 HZ HUM, MORE SERIOUS.
IF THE AMP BUZZES...
This Buzz is 120 Hz Ripple, and this is not all that bad, and hope is knocking
at the door.
The Buzz can also be Heater to Cathode Leakage noise and this is more like a
hard Buzz, and worst case 60 Hz Hum.
AC Filaments operate a 60 Hz (or DC).
STEP9:
IF THE AMP PLAYS WELL FOR 15 MINUTES, ADJUST THE BIAS (IF BIAS IS ADJUSTABLE) THEN LOOK FOR RED PLATES ON POWER TUBES
AGAIN IN A DARK ROOM.
YOU MAY NOW HAVE AN AMP TO BE MONITORED FOR A FEW DAYS
NEVER LEAVE A TUBE AMP ON
AT HOME "ALONE", TURN IT OFF
THE SUBJECT OF AMP AND PREAMP NOISE, BUZZ & HUM
Now I want to get this one off my chest, silent idling classic Tube Amps are a
Myth.
All classic tube amps make some type of noise when idle, but the goal, to
address and reduce these noises.
Tubes are great at amplifying the last minute signal or unwanted noise.
So when your speakers are buzzing or humming, check your sources.
More often than not those small Streaming Boxes will send a noisy signal to that
first Vacuum Tube in the amplification gain stage, so try to isolate this first
before blaming your Tube Preamp or Amplifier(s).
60 HZ HUM? IS THERE SUCH A THING? YES! BUT NOT WHAT YOU BELIEVE...
I hear this term all across YouTUBE Channels, and really wonder if anyone has ever
really heard 60 Hz Hum?
Highly unlikely....
My friends, 60 Hz Hum is a catastrophic noise, if you ever hear it, the next thing you want to DO IS PUSH the OFF switch.
60 Hz Hum is a rare occurrence something is off in the Power Supply or a AC Power
Like leakage into the DC Supply.
The Law of Superposition allows both AC and DC to coexist on the same wire,
node, pin, etc.
60 Hz Hum is when
Rectifiers may fail, Filter Caps conduct DC current
Or a less than ideal Vacuum Tube might
be leaking 60 Hz; from Heater to Cathode
60 Hz Hum is what you hear when AC Power line 60 Hz (or 50 Hz) sinusoidal alternating current and voltage
from the Transformer Secondary (or far more sinister the Primary) makes it to
your Woofer Cone.
60 Hz is a fault when leaking or passing through AC made it to the DC Power Supply rail
It somehow is sneaking past the
Power Supply rectifier and/or filtering sections, or both.
60 Hz Hum
this will make it to your Woofers and WOW.
They do shake, and sometimes, the Voice Coil melts, Ouch.
60 Hz is a low, very low frequency, it is not a Buzz, but a very deep HUM.
Imagine that the low string on a Bass Guitar goes down to 41 Hz... pluck
this and listen.
Now think about a frequency some 20 Hz above that, and you can find this on the
Bass guitar fret board
by examining the chart below;
On the Bass Guitar E string, go to the 6th Fret and that is 58 Hz, while the 7th Fret is 62 Hz.
In 50 Hz Countries that Bass Note is on the 3rd Fret on the E string at 49 Hz
practically 50 Hz.
Pluck those and see if you hear a Buzzing Sound?
So the next time YouTUBE Musicians or Buzzword slingers are in a studio or
creating content,
complaining about their Single Coil Pickup 60 Hz Noise and their Tube Amps 60 Hz
Hum... hummmmm.
60 Hz Hum is not a buzzing noise, it is not your Single Coil Guitar Pickups.
Single Coil Pickups are prone to amplifying Common Mode Noise and inductively
couple to stray Electromagnetic fields.
So 99% of Musical Instrument Cables are Single Ended, not Balanced, prone to
picking up garbage.
This is why a good Wireless Guitar Transmitter de-couples the instrument from
the Amplifier
and hence protects from these kinds of things we refer to as Hum or a more
accurate and correct Buzzzz...
60 Hz Hum is a defect somewhere in the Electronics, mostly from the Power Supply or
even wiring mistakes.
It can also be due to improper, but well meaning introduction of a 3 prong AC
Power Cord in a Classic Amplifier.
People hope that Grounding a 2 Prong Classic Amp with that 3rd Safety Ground
bonded to the chassis
is a great upgrade.... not always, unless the DC Grounds are isolated from the
Chassis... huh?
Therefore
60 Hz Hum is a Power Supply failure where the Rectifier Short Circuits,
the
Filter Caps fail or there
is a major malfunction of the Power Transformer or a Tube.
Some Plate and Filament Transformers do fail and this is pure 60 Hz madness, and
also a shock safety issue.
What people miss-label 60 Hz Hum mostly "ripple" of 120 Hz Rectified DC.
Generally
Hum can be created by induction between improperly routed wires, especially in DIY builds (I
know).
If you don't know what a Rectifier or Rectification is, or does, what it means, read
up.
A strong 120 Hz ripple is what we hear when the equipment is not properly DC
Grounded
Or the Power Supply Filter Capacitors are struggling to do their job.
Yes aging Power Supply filter capacitors, these are toxic.
In fact Power Supply Buzz is far more
common than you know.
The we then have a situation called a Ground Loop, especially with Turntables.
Tube Amps will ALWAYS have some residual 120 Hz ripple, it is almost impossible to
extinguish.
As long as you cannot hear it from your listening chair, you are covered.
But it your Woofer vibrates, something if wrong. A light buzzing sound is normal
for Vintage Tube Amps
and also Preamplifiers, where the Tubes may be past their prime. Hum can also
come from bad New Tubes.
Believe Me I have had my share of Bad New Tubes and Hummy NOS Tubes.
Unless you own a Tube Tester that tests for Noise, the acid test is in the
equipment.
Eliminating 100% of Buzz in Classis Old Tube Amps is a worthy but unattainable
goal.
Unless you power your whole Tube Amp System from DC batteries.... you replace
the Ripple with Battery noise...
120 Hz Buzz (Hum) happens with all kinds of Audio Gear and its not limited to
just Amplifiers.
Preamplifiers also suffer from 120 Hz Hum (ripple) and it is very annoying.
Electric Guitars pick up 120 Hz ripple from their Cables and Amplifier and
Pedals....
The solution here is to troubleshoot and isolate the culprit, there is no other
way.
We can only reduce 120 Hz ripple, as every DC Power Supply always has some
ripple.
The less ripple, the quieter the DC rail.
If you want to know more about Grounding, pick up a text and read.
Grounding is one of the most misunderstood topics in Electricity.
Just as people still to this day speak of 110 VAC, another misunderstanding.
Only experience and learning provide the basis for understanding.
CALLING
60 HZ HUM, 120HZ RIPPLE OR GROUND LOOP NOISE
IS LIKE CALLING APES,
MONKEYS
No matter how many times we try, people still call Orangutan, Gorilla and
Chimpanzee - Monkeys.
My answer here, open a Book and Read, swipe that iPhone and get your facts straight.
Don't rack up $200K in student loans, before you understand the fine print.
A College Degree, is what you make of it, while some Degrees opens Doors, others
cannot.
A College Degree should be a version of what
You
Love to do, but be very pragmatic.
Trades are a great alternative to a College Degree
Ask yourself the difficult questions, before signing a Government Student Loan.
If you love Marine Life, and have has a passion for it from Childhood, and have
self educated
and participated in local Marine Biology related activities
Yes go for the Marine Biology or Oceanography Degree.
If you have never been to a Beach, imagine what Marine life is about, think again....
Also and unfortunately, College Degrees are mostly over priced
They are also "over sold" at Name Brand Universities &
through Government Loan programs.
The Student Loan is nothing more than a "Weaponized" Monetary Instrument.
Government sponsored Student Loans are just like a Time Share contract.
It can end up like a Scam turned into a Government Monetary instrument for some.
NOBODY can guarantee a job, NOBODY.
Entitlement is not a skill......
If you ever heard of a Time Share, then the Student Loan weaponizes loans,
like a Time Share does.
What do I study?
Just like betting on a Snail or a Rabbit in a race, today the STEM degree is the Rabbit.
It is a shame that today, Humanities do not pay bills or give a decent living
Even Teaching is a broken profession now, a crying shame.
The same de-humanization is
progressing at an advanced pace...
rapidly escalating into Opioid and Alcohol addictions
How can any educated person think that Cocaine is safe?
I am dumbfounded by the level of ignorance of reality these days.
THIS MY FRIENDS IS AN TUTORIAL ON 60 HZ HUM
AN EXAMPLE OF SLINGING BUZZWORDS
JUST LIKE 110VAC, ANOTHER MISNOMER BUZZWORD
EVEN ELECTRICAL ENGINEERS WITH DEGREES STILL UTTER 110VAC
WHY? THEY DO NOT MASTER THE SUBJECTS, JUST PASSED TESTS
THEY NEVER HELD A VOM AFTER COLLEGE.
THEY JUST REPEAT THINGS.....
MY
TUBE AMP JOURNEY - EARLY TO PRESENT
The photo below was developed and enlarged by Me.
I was really into B&W film photography and probably Tri-X judging from the
Grain of the photo below.
I developed and enlarged the photos at home.
A hobby my Grandfather enjoyed with Me.
My Camera was an
Olympus OM-1 Black Body SLR, Zuiko 1.7 Lens
My Enlarger was a Bogen T-35
Boy... I miss that OM-1 w/Zuiko 1.7 Lens
That Camera was awesome until it was stolen from my house.
I also miss B&W Photography
It gave me a manual ability that Digital does not
offer to express myself.
Then I also used to set my Shutter and Aperture manually, as real Photographers
develop
a special sense of how best to set the Camera for amazing Negatives
Microdol for Film, Dektol for Paper, then every now and then experimenting with
boosting the film speed with special chemicals called ACCUFINE, tons of fun.
B&W PHOTOS CIRCA SUMMER of 1975
i was into elton john, black sabbath & alice cooper
led zeppelin, aerosmith, pink floyd, the who, YES, BOB WELCH, STEVE MILLER,
foreigner
camel, elo and more of those old bands we boomers grew up with
yet ATTITUDES HAVE NOT CHANGED MUCH I CAN SEE......
Then, i went on the HF BANDS
WITH CW - morse code in the 1980'S
DOZENS OF CONTACTS AROUND THE WORLD
"In The Beginning"; Yoda created the LP once
Edison proved it worked...
It all began....., in a Neighborhood....., far....., far away
On a lush tropical island, back in 1973 A.D. when I owned and enjoyed my first
1950's Tube Amp
ironically I was not impressed when comparing that old 50's Tube Amp
to the fabulous Solid State of those times, yet I was lucky to have an
Amp at all.
#1 - My very first Tube Amp from the late 50's - Mono
in 1973
So here is my very First Tube Amp - was a
used "Dictograph" Mono-6V6
my only known B&W photo is shown below
the nice color photos.
If I ever find the Negatives, I may have more Pics from that day.
These Color Photos, are from a Reverb posting, great pictures, brings back lots
of memories.
This Tube Amp lover, made a nice wood/formica front panel, preserving the original
Faceplate/Knobs
Now that is creativity, I recall the threaded shafts were quite long.
The
original cabinet
was made of plywood and a nice dark oak veneer.
The cover was removable.
My Cousin, deliberately left the amp ON when we went to the Mall
I specifically asked Him if He powered the amp down... He said YES.
I was around 13, He was just 11.
My cousin was a rascal.
When we returned Home, the room was full of Smoke, the fuse did not Blow
and the Power Transformer melted......
He thought it was funny, I was upset.
NOTE THE OLD ELECTROLYTIC CAPACITORS - THESE REALLY GOTTA GO!
BUT IT LOOKS SUPER CLEAN.
THESE RECEPTACLES WERE MOTOROLA TYPE F
I WOULD REPLACE THE METAL CAN CAPS RIGHT AWAY
THE AMP IS IN GREAT SHAPE, OBVIOUSLY NOT IN HUMIDITY
Current status - some unknown Landfill in Puerto Rico
The Amp was thrown in a dumpster in 1975... a sad day, I was young and
careless.
Then I had a Solid State Youth, until I turned 35, when Tubes became my
paradigm
I would
Play Billion Dollar Babies until my Neighbor complained
I had a 45 rpm of "You won't get fooled again" and we used to scream
along with Roger
"Night's in White Satin" 45, with "Cities" on the flip side.
The Monkees, and lots of 60's LP's were played, the Age of Aquarius was
finally here.
I was very young, and just starting to open my eyes to the 73' Arab Oil
Embargo.
The Americans would ask me; "What is Hay Gas?" alluding to the signs at
the Gas Stations.
Hay Gas were the signs posted at Gas Stations, the Non-Spanish readers
would ask me
"What is Hay Gas?", I would tell them Hay in Spanish is "we have" or
"there is"
So much for Gas made of Hay :) hahaha
Too many Gas stations would run out and the lines of Cars were long
Overnight, Gasoline went from 0.35 Cents per Gallon to 0.78 Cents.
Mom could no longer fill up our 1971 Chevy Nova with a $5 bill with change
leftover
We entered the new Petro Dollar OPEC backstab, when we make shady deals
with Shady folks.
#2 - Philco Stereo (Grandpa's) - 10 wpch, 1975
Current status - Same unknown landfill in Puerto Rico
The next Stereo was a Philco that came with a separate Turntable and
Speakers all of the same brand.
After I threw out my Mono Tube Amp I was amp less for probably 5 month's.
This was Grandpa's Stereo, I asked Him for it as it was sitting on His
shelf for at least 5 years, abandoned.
The photo above is the next model in the line, as I don't find a photo of
the actual amplifier.
This was typical of those times in the late 60's and early 70's when folks
purchased
$200 Stereo's with Speakers, Turntable and Amplifier, speakers that a
"breeze" could Blow Over
I wired a Headphone Adapter into the RCA Speaker Outputs and basically
used a pair of SONY DR-5 Headphones
on the Amplifier Output, awesome sound, but I could not turn up the volume
past 2 O'clock as I would have gone deaf.
This amp saw my Zeppelin, A.Cooper, B.Sabbath, The Who, etc. Rock formative
years, as I started to smoke Marlboro's
This amp was at my first Beach House pre-drive's license party,
Charlie had a Red Toyota SR-5, and was old enough to drive.
We went out there with Charlie, David, Derek and Howard for some "under-age" Brown
Glass
Heinekens and some fine Colombian
We played Dark Side of the Moon, about 20x, and a few other Rock Albums,
we goofed around and had a blast
at midnight we went across the street to the Beach, enjoyed the Moon
and the Cool Water
We had a blast, as I was initiated into a new realm of zero parental
supervision
We were free, appreciative and super responsible
We left the Beach House sparkling clean and took the trash with us.
Unforgettable weekend, and many more Beach House events that unfolded.
#3 - Pioneer SX-450, 15 wpch, Ft. Buchanan PX - 1976
Current status unknown - a thief stole this one from my house
Speakers were my friends Olson's from Texas a popular Japanese US Audio
Chain store
Pioneer was purchased new at the Ft. Buchanan PX in probably late '76
The amp lasted about 5-6 month's, then
my Home was broken into, so this Amp and the Pioneer PL12 Turntable were stolen
along with the Kentucky Fried Olson's (victims of a CYGNUS X1 overload)
I toasted the Olson's by pushing CYGNUS X-1 to insane levels.
The Rocket Audio did them in.
If I recall correctly, this Amp had a
cost of about $150.00
The PX used to get the Japanese products, way before the local market, they
came direct via AFEES from a Far East Warehouse.
Sadly, I did not own or enjoy the Pioneer long enough but I do
recall the following
My friend's father's face when I played "Fly By Night" for Him, on my
Sennheisers, His smile was unforgettable.
The other Memory was when Fico came over, with a brand new "Wish you were
here", with that dark-blue plastic covering.
I recall the cold Bottle of Blue Nun White, and some Swiss Cheese.
Fico laughed himself out of the room as soon as the Band came in
after that long intro to "Shine On You Crazy Diamond".
I was left alone, with the rest of that album, it literally altered my
perception on Music with Sound effects.
He asked me to return it, after I made a Cassette for our 1973 Civic....
played it over and over.
Actually I took the LP to High School, and remember Nick Matos making fun
of the cover and inner sleeve art.
My memory is both a Curse and a Blessing.
Technically I am able to recall specs, numbers and details from 50 years
ago.
But, I cannot seem to remember people's names unless I call them a few
times.
Yet I never forget a face or a piece of equipment that came across my
life.
#4 - Technics SU-7300, 41 wpch, Ft. Buchanan PX - 1977
Current status - gifted to my Cousin whose Son Marcus, kept it playing
As I went through a few rounds of my Lawnmower/House
painting money
I paid $175.00 brand new in 1977.
This amp lived with me for many, many years and never gave up!
As a HS student, buying a Technics SU-7300, 41wpch & Bose 501 Series II phase
from '77 to '86
That was big news in my small circle of friends, this is my RUSH
amplifier 2112 and Xanadu
The Bose 501 speakers, I purchased @ the Sabana Seca PX, because the Ft.
Buchanan, did not have Bose.
The story of the Bose 501's, I actually had purchased Technics SBX-50 3
ways 1 month prior.
The Bose, I purchased at the PX for Mom's cousin Angel.
But when Angel heard my Technics SBX-50's, He just fell
in love.
Current status unknown - Traded for Bose 501's
So I traded out the Technics BSX-50's, for the Bose 501's.
Bose 501's were gifted to Gary Bonderenko and
I had replaced both 6 Ohm 10" Woofers
Angel was into Sibelius, I
was into Deep Purple, 501's offered a more realistic Rock user experience
Today I would have wanted the SBX-50's as my Musical fortitude for High
Decibel Music has waned
Then many, many, too many of Vega Baja Parties - if you remember being
there, you were
definitely not present :)
This Technics SU-7300 amp went from P.R. to FIT, then back to P.R.
when I graduated
I mailed it and the Technics Turntable to my Cousin Jorge
in Tampa, when I got an Onkyo.
Jorge was awesome as He sent me by Air Freight a ton of my College
things like a SHARP Color TV, etc.
He was a trooper, and did me the Huge Favor as I had left my stuff at
His house in Melbourne when I graduated FIT.
The SU-7300 was with me during my full 4 years of FIT College, I found a photo below of my
Southgate 1985 dorm.
This amp would just Blow Fuses if pushed hard, but always worked.
If my memory is
correct this amplifier used a "Current-Mirror" circuit topology.
GRISSOM HALL, THIRD FLOOR DORM 1982
FIT APARTMENT 105B SOUTHGATE 1985-86
BELOW AFTER I GRADUATED COLLEGE AT MOM'S HOUSE IN PR
JUST PRIOR TO MY ONKYO 105 WATTER
HECTOR ALEMAN GAVE ME THE TECHNICS EQUALIZER ON PHOTO ON LEFT
AND THE OLD CASSETTE DECK THIS WAS 1987
THAT DECK RAN SLOW, BUT WAS FREE!
#5 - Onkyo Integrated, 105 wpch, '87 w/Tuner
ordered by
phone; Stereo Discounters, MD.
(Stereo Discounters had a healthy Mail
Order business in the 80's, BUT closed the year after I ordered my Onkyo)
https://www.mcall.com/news/mc-xpm-1988-03-11-2613214-story.html
Current status unknown, gifted to Len Elias who used it well
Also purchased a pair of Infinity RS-101, 2 way speakers from Plaza Las Americas.
The Stereo Shop that was across from La Esquina Famosa, next to the
Gorbea Eye Center
I just cannot remember the name of the Store, but they sold all types
of Stylus and Phono Cartridges
Gifted to Chris Fauser in 1992 in Lynchburg, VA
When I worked at Rosy Roads, used my Paycheck, no
more Mowing Lawns.
On Base I almost doubled my Pay, by leaving Motorola, but would return
to Moto one last time until 1991.
This amp was the highest power I had or have even owned.
I fried my Bose 501's
Tweeters with Yes songs, cranked up' to insanity levels.
These Infinity Speakers were the replacements to the Bose 501's.
this Amp eventually got the
Tropical Salt-Air Blues so I gifted it to Lenny
before I departed Puerto Rico for the Mainland in 1991
Lenny who
got it going, enjoyed it, until again.
We took it out to Vega Baja and I blew out my JBL LS500 tweeters on Alan
Parsons "Instrumentals"
so the hearing protection was
optional, and recommended.
The JBL LX-500's were from Circuit City, Lynchburg, VA and I had brought
them back Home in 1996.
Prior
the JBL's I had
Cerwin Vega VS-120's that were okay sounding.
But I was never impressed,
the JBL's were a far more refined sound.
Circuit City had a no questions asked trade-in policy for Speakers
So I took the Cerwin's in after 4 month's and walked out with the JBL' 3 Ways...
Man those JBL's really sounded musical, and lasted until I replace the
Tweeters with an EBay find
and gave them to Lenny who I hope is still enjoying them today after a few
Woofer Re-Foams.
Note that Foam and Rubber Woofer surrounds only last 5 year in the tropics
if lucky.
Rubber Belts turn into Goo and sometimes become Green with fungus
My Linn LP12 Belts would last about 5 years before succumbing to the Salt
Air
This Onkyo was amazing and I loved the Remote Control....
#6
ADCOM GTP-400 and GFA-545, 100 wpch - Audiotronics Roanoke, VA.
Financed with AVCO; close to $1100 USD for both w/ VA Taxes
Current status SOLD on EBay, GTP-400's do not age well
Current status OPERATIONAL. ADCOM made awesome Power Amps
Tuned-up at Audiotronics in 2011-12 and still pushing out 100 Watts/Ch
in 2023
Financed at Audiotronics, Roanoke in 1992, I still have the GFA-545 Amp, I sold the Preamp
years ago...
These were used initially with the Cerwin Vega's then settled with the
JBL's.
The FM section on the GTP's are notoriously bad, mine was no exception,
the factory could not fix the FM.
Sensitivity was so bad, FM local stations would barely register on the
signal meter.
In 1997 the GTP-400 Source selector switch, developed an intermittent Right Channel
Not even an Authorized ADCOM factory service in New Jersey could fix.
The GFA
Amp returned to the US in 2010, and I took it into
Audiotronics, in 2017 for a tune-up, still works like a champion
The GFA rocks my Zu Druid speakers as my ROKU-NETFLIX/YouTube basement
setup
The GFA is driven by an Onkyo Solid State Preamp from EBay, it is musical
as can be for $99.00
So I can suggest a old Solid State Preamp with a Tube Power Amp is a great
"Entry Level" combination.
Unless one can get a not-so-noisy Tube Preamp, a Solid State Preamp is a
cleaner entry level pathway to Tubes.
I use my Transcendent Sound Phono Stage into the $99 Onkyo Preamp,
bypassing the "On-Board" RIAA
What I love about the Onkyo, the Bass Loudness Control is variable, and
I can dial-in the heft for Movies and Sound Tracks.
For sound effects, nothing is belter than Solid State; THX, Dolby, etc. all synergize well with Movies.
Also Multi-Channel Home Theater is almost always the exclusive realm of
Solid State.
I can unequivocally state that ADCOM GFA amps are a quality product,
ADCOM Preamps, mostly so-so.
The ADCOM GTP-400 Preamps are victims of the "large single PC board" syndrome....
My humble opinion is that
separate PC Boards would have improved the ADCOM Preamp reliability, but
driven up cost
The GFA series Amps are tough as nails, even used it once to amplify a Band
at my Beach House...
ADCOM GFA's are great for bright - edgy Speakers, these amps are very
smooth and relaxed
Some even describe them as 'dark sounding', I just love them for being
smooth and refined, laid-back.
I began in 1992 with the Infinity Speakers, but then I went for the Cerwin
Vega VS-120's
Traded back to Circuit City in 1992 for JBL LX500's
These could Rock, but were far from refined, actually they were not a good
match with the ADCOM GFA amplifier.
The sound was edgy and bright, maybe they just needed to break-in. After
about 3 month's I grew tired of them, and
they would blow their Fuses when I cranked them up with my Thorens TD-280
Turntable so...
I went back to Circuit City and the Salesperson told me that they had a
no-questions asked Speaker Trade Policy.
I took these back and left with a Pair of JBL LX-500's, now I had the
Music I was missing.
The salesman at Circuit City in Lynchburg VA was actually a Sales Woman
Unusual for Hi-Fi Stores, but very cool indeed, She knew her stuff well.
Traded-in the Cerwin Vegas for the LX-500's
Now these JBL's delivered great music
#6
BOSE 901 Series IV - Lynchburg, VA.
From these speakers I moved back home to Puerto Rico and did two things.
I made my Oak 2 Way AUDAX Bookshelf Speakers and also bought a pair of
Lowther 1.3's
These JBL's lived with me for many years until I got a pair of Zu Audio
Druid MK4's in 2006.
that are my main speakers to this day. Apart from Pilot PSV-2 and Bose
301's.
My High School Algebra teacher and Soccer Coach gave me a Pair of Bose
901's that I eventually
gave away to my Friend Joe for His Birthday.
I enjoyed the Bose 901's but
thought that Joe could make better use of them.
Bose 901's are best for DVD and BluRAY Live Concerts, they just make
it seem real in bare walled rooms.
LYNCHBURG VA BOSE 901'S
I have not purchased any new or used Speakers since 2016 and I don't plan
to until maybe 2026 when I
plan to lay down Cash, or Finance a pair of $5000-10,000 speakers, the sweet spot
between elegance, forgiveness and freedom
to play lots of recordings both Good, Not so Good and just plain raunchy
but tolerable.
IF THERE WAS ONE SINGLE INSIGHT TO NOTE ABOUT OLD
TUBE EQUIPMENT
WHEN THEY ARE
OVER 50+ YEARS
OLD, THEY ARE NO LONGER REPAIRS
THESE ARE ACTUALLY
RESTORATION PROJECTS
Stromberg Carlson AV-39 Mixing Preamps
- In the queue for a restoration
NOTE: This manual was prior to ZIP Codes
Dallas 1, TEXAS..... that's old time
before this stamp 4 sure...
MY "MOLESTED" MARANTZ EPISODE
EXORCISING "EVIL" UNCLEAN LEAKY POWER SUPPLY FILTER CAPACITORS
My last fix before moving
away from my Puerto Rico in 2010
It's been 12 years and counting, since these Marantz
came across my workbench, rare pieces indeed
MacArthur once said it well "I shall return"
The older they are, the better to "Molest"
and Upgrade...
The Marantz Tube Preamp and Marantz 9's needed a few oozing/leaky/crusty
Electrolytic Capacitors replaced
These arrived at my home virgin, Un-Molested. I popped the bottom covers and
found electrolytic capacitor goo on the bottom plates
Rule #1: With old classic amps, NEVER JUST PLUG THEM IN AND TURN THEM ON.
Always perform a visual inspection and don't believe in Santa Claus or Reforming Electrolytic Caps.
When Electrolytic Caps are more than +40 years old.. OUT THEY GO.
And Yes, I am of the school of thought that Amplifier
Molesters are innocent of all charges, most of the time.
Just changing parts and components, for the heck of it, to please the 'imaginary' goal
of 'sounds so much better'
that is not my game. But I do not doubt that a $110.00 Vcap sounds great, they
do, i use them sparingly with awesome results
But the magic, the real art is knowing if the Classic can be improved with
just simple things.
I change parts only when necessary, by inspection and measurement, not imagination.
There are a staggering number of YouTube videos that claim to show how to reform
old capacitors
The
famous Marantz 9 Tube Monoblock Amplifiers
Yes I actually worked on these and enjoyed every
last minute
The Marantz 7 Preamp was in better electrical shape.
The Marantz 7 Tube Preamplifier
THE AMOUNT OF MONEY PEOPLE PAY FOR THESE CLASSIC MARANTZ IS BEYOND ME.
I GET THAT THESE ARE RARE, BUT AS FAR AS PERFORMANCE, AT 1/2 THE PRICE ONE
CAN DO MUCH BETTER
IF WOULD RATHER BUY A BRAND NEW SOLID STATE PREAMPLIFIER WITH
ALL THE BELLS AND WHISTLES
AND LEAVE THE TUBES FOR THE POWER AMP DUTY.
VACUUM TUBES IN PREAMPS ARE GREAT, BUT THE NOSTALGIA SOON FADES
WHEN
YOU START TO SPEND MONEY ON LOW NOISE TUBES INSTEAD OF WHERE
IT'S REALLY NEEDED.
TUBE PREAMPS ARE INHERENTLY NOISY CREATURES, AND I SOLVED
THIS ISSUE BY BUILDING A FEW AND REALIZING I WAS ALQWAYS
FIGHTING THE NOISE.
NOW I USE A $99 DOLLAR EBAY ONKYO PREAMP AND THE NOISE IS GONE.
I AM SAVING UP FOR A BETTER QUALITY SOLID STATE PREAMPLIFIER
AND MY TARGET IS GOING TO BE AN ACCUPHASE SOLID STATE
PREAMPLIFIER, THAT MY FRIENDS IS MY HOLY GRAIL.
My special version DYNACO SA-35 Stereo Amplifier
Sweet, sooo, SOOOOO sweet.
If this one had real Z-565 OPT's OMG!!!
But these newbies OPT from DynakitParts are awesome.
I do miss not having a 16 Ohm tap as I don't own of like
4 Ohm speakers, I avoid them unless I have to own a pair.
My Audio Speakers are all 8 Ohms or higher.
How's that, for an opinionated 62 year old geezer.
6.12.22
Great musicality
The sweet sounds of the classic ST-35 circuitry, very polite Bass
Quite musical, non fatiguing sound, marathon listening capable
Secrets shhhhh: I have a pair of real NOS Acrosound 4-8-16 OPT's lined up for a future
SA-35 Build
I may offload the SA-35 below, if you are interested just e-mail me, I am open
for trades.
MULLARD 5/20 MONOBLOCK AMPLIFIERS
THESE ARE REALLY WORTH BUILDING
I SHOULD MAKE SOME PC BOARDS.
7.11.22
Sharp, nimble, detailed & precise, good satisfying tight Bass
The EL34 optimized for 6600 Ohm Push-Pull Primary
Design Circa 1959
This is the amp I would recommend for all around listening
8.13.22
My AIKIDO now has V-Caps....
OMG, the detail, the dynamics and the clarity
Just like Legally Blonde - "Bend & Snap"
As soon as I pushed Play on my NjoeTjoeb CD player
the world suddenly became a better place
SR-91
AURORA 6F6 STEREO NFB PUSH PULL AMPLIFIER
Loving the 6F6G Tubes from Ikraine
I ordered a fresh Octet of Russian 6F6S from Kyiv
on EBay, I hope this senseless War ends.
I have been ordering Tubes from this Ukrainian seller for at least 15 years
Top Shelf Tubes, zero BS, well packed and super reliable.
Packages are taking 30 days from Kyiv now so be patient.
YES WE HAVE ANOTHER WAR, NOT THE EAGLE BUT THE BEAR
I write these words as V.Putin keeps throwing influential people out of
Windows.
V.Putin is in a very expensive, self-delusional, KGB, Stasi-Nazi-Hunting
Safari Special Operation
He needs some Tube Amplifiers, and Music to calm His mind down.
It makes no sense to be in a Demographic Cliff and then send your Young Men to
Die.
Wars really screw up the Gene Pool, we lose good Men, often for nothing worthy
other than a Dictator's whim
This has been true for as long as Men (and Women) die in Battle.
We never send the Weak and Feeble to War, until now, so the
new Battlefield is de-evolving right in front of our very Eyes.
When older Men defend their Nation, the more able Soldiers can be more
effective.
The invader must be very careful to volatile sovereign nations
Unless you wipe it all out and kill them all, Guerilla Warfare will be the
invading nation's downfall.
In our Country, we use Prisoners to make License Plates and to Weed the Highways
V.Putin uses Prisoners to do His dirty work, and they could not GAF.
Hey V.Putin, give me a Call, I can suggest a few Tube Amps for your
Tchaikovsky Collection....and your Warmongering obsession.
TELARC 1812 Overture can soothe your anxieties...
Now back to the Aurora...
The Octet of Russian 6F6S have arrived to Rochester
The
Parcels from Ukraine are slow moving.... as expected
But the fresh 6F6S have arrived.
I will Tube-Up and place the Aurora in Service
with my Focal 706V's at 8 Ohms
I have my collection of Jazziz CD's all lined up
My Pilot PSV-2's will be on duty at my Cousin's home
They will look great I am sure.
BEFORE THE NEW TUBES, PRIOR DUTIES IN VIRGINIA
6F6 METALS ARE GETTING SCARSE..... THEY WORK WELL.
This is the amp above that inspired me to build my first all Tube Guitar Amplifier...
The NeoClassic30 is 1/2 of this amp with a 12AX7 Preamp in front of the 6J5.
My September Amp Rotation
ROTATION
START DATE (September-October, TBD)
AFTER THE NEW RE-TUBE ON 9/10/22 IN ROCHESTER
The 6J5 are Italian FIVRE with the Italian Government Stamp
The Rectifiers are 5Y3 from www.angela.com
(the prior had 5V4) SOVTEK badass tubes
The 6F6S Tubes are from Dmytro in Kyiv
The 6SN7's are Chinese SINO, wonderful and musical, they need plenty of
break-in to smooth out.
I plan to fire this up soon with the Focal's and also the Focal 706V.
HERE IS THE LATE SEPTEMBER AMP ROTATION FROM 9/23/22
BUT MY CAMERA BATTERY WENT OUT SO I TOOK THE PIC TODAY
Photo - Rochester NY
7AM
The Ukrainian/Russian 6F6S Tubes are on-duty
All Glass, NFB Push Pull Stereo Amplifier
When was the last time you heard a Push Pull Triode Amp
with no Feedback?
My FM Tuner is picking up Listener Supported Jazz 90.1 Rochester NY
The station is very near my QTH so I barely need an FM Antenna
The new item in the photo is the D'Addario Power Center
It's the best $50 you can spend for AC Noise Filtering, cheapskate alert!!!!!
(myself included)
https://www.daddario.com/products/accessories/power-solutions/power-cables/tour-grade-power-base/
FALL IS HERE!
THE LEAVES ARE STARTING TO CHANGE
9/26/22
UPDATE... SINGLE TUBE FAILURE
ONE OF THE NOS 6F6S TUBES LOST A FILAMENT
IT OPEN CIRCUITED, WENT DARK.
I had 3 spares so I dropped one into the amp and done.
When buying large groups of Tubes, I often expect some fails.
11/12/22
Winter has arrived in Rochester!
The cold weather has me playing Guitar in my Basement, and I am going
ELECTRIC.
So far I have not had the motivation to build something, but....
THE CATHODE FOLLOWER AMP IS CALLING MY NAME
ALSO THE CAT-1 PREAMP KIT IS YELLING AT ME.....
During the Holidays, I will make one or both...
Future Amplifier Audio Schedule:
KISMET 1.0, ShermanAudio Dynaco MK3's , Atma-Sphere M60 MK2.3
Owning multiple Amps requires using them all
Leaving an Amp sitting idle for more than 6 month's is not suggested
I also am building the CAT-1 Kit and the Cathode Follower from Bruce
Rozenblit
I want to ask Bruce for a Front Panel... I will send Him a message to see if
He has one
for Sale...
Q4/23 Office Audio status report
Smooth Operator, Multi-format Music inside of the Wireless Age, the clash of
formats!
ONKYO P-301 Preamp, SA-35 Tube Amplifier, TEAC Cassette, OPTONICA FM/AM, Njoe
Tjoeb CD
Bluetooth Stereo Receiver, Denon DCM-360 HDCD Changer, Focal 706V, Balanced
Power AC Transformer
Current -
Q2/24 Office Audio status report
Now this got interesting. I managed to get my Olson AM-240 operational after
20 years. This amp was super problematic, it had a bad Power Switch that
finally failed 8 years back. I tried to get it working smoothly but it kicked
me back. So the culprit was that when I was recapping this in San Juan in 2003
I left a Left Channel Phase Splitter wire disconnected! It was always
distorting on the Left Channel.
So now after a few hours on the Bench, I have it working with all good Tubes,
especially the 7189 Russian version 6p23pEB that are amazing at 430 Volts on
the plates. This amp puts out 23 watts solid just before clipping.
The sound is quite nice, and I am glad that in the past, some owner did not use
this amp with
normal regular 6BQ5/EL84 Tubes. Despite popular Lore, the EL-84 will not work in Amps that
need real 7189. But on the contrary 7189 will work perfectly in EL84 amps.
If a 7189 amp operates the plates under 400 VDC then a 6BQ5/EL84 might be a
suitable sub. But why risk the Output Transformer primaries. When a
6BQ5/EL-84 tube decides to run-away, it can often melt the Output
Transformer primary bobbin wire, causing a catastrophic failure of the
Primary, and an expensive re-wind if you can find a place that does a good
rewind.
If you use EL-84 Tubes in an amp that has more than 400 Volts on the Plates, I
wish you a long life, as neither the Output Transformers, and Power Tubes will
last long. And if the Primaries of the OPT don't burn, You got lucky. I had an
AM-240 that was roasted that I traded for the Top and Bottom Covers. I traded
for my old Harman Kardon A-300 and 8x 12AT7 Telefunken Tubes.
Good trades, meh. But I am glad this AM-240 is kicking A again.
I replaced the loose Volume and Balance knobs with Black/Silver Radio Shackers
and now I canm actually see their
adjustment from my Chair. The original skinny knobs are had to see where they
are in their rotation.
One thing, this amp uses the hard on RCA cable input jacks like old Pioneer
and Sansui. So you are best using normal RCA Cables, the good stuff does not
fit and usually hums
The Phono Stage is great as well, it had an open 100K Voltage Droppinf
resistor that I finally found, as
the Phono stage was broken since I bought this on EBay back in the early
2000's.
I also have my old ADCOM ACE-1 AC Enhancer that saved my System in a 1999
Y2K Party.
New AC Power Switch installed, I had to snip off some metal so that the
switch could just push into the existing rectangular
front panel opening. The AM-240 is amazing, the factory Output Transformers
have terrific Bass.
Now all I am waiting for is the replacement ALPS Stereo Volume 500K
w/Loudness Tap
plus the 0.047uF/600V MPW Illinios Capacitor Poly Caps to replace the
Brownie 0.047uF NTE's
that are not known for being the ultimate in musical prowess. My strategy
with restoring
old amps like the one below, is not knowing in advance whether it will ever
be a reliable daily player,
I prefer to use standard economy 600V Signal Caps until I know for a fact
that the Amp will play. In this case I ordered the (4) Replacements and
changing
them will take me no more than 30-45 Minutes depending on the Oscilloscope
test for inner and outer foil orientation, that I always try to respect with
signal caps.
The Headphone Jack is next and I also plan to re-wire the Tape Head input to
a normal
Tape Mon input as nobody today uses Tape Decks that just has the Head
connected to the RCA
jacks with no internal Tape Head stage to correct the curve, similar to RIAA
but for Tape Heads.
The Tape Head input is one that went obsolete many decades back, and in this
AM-240
is just a Wasted Input. I will have to bypass the Tape Head equalization and
connect the RCA
directly to the rear of the Phono-Tape HD switch, easy enough for Me.
MULLARD
In the book below, you cannot purchase any of these designs, they
all just plans to be
made by hand.
This book is full of wonderful schematics just
waiting to be discovered and assembled.
There are som many secrets in this Book, about Push
Pull amplifiers that most
readers will gloss over them.
The few who have actually built Mullard Amps,
have likely faced adversity, then pure sonic bliss
The Mullard sound is unlike any "Push-Pull EL34".
These are authoritative, direct, and have
rock solid
stable performance with lots of musicality
It is evident from the Mullard Book, that the
designs, were optimized around the EL34, EL-84, ECC-83 and EF-86.
These amps have excellent amplification
measurements, and require very little drive
In fact I would advise NOT to
use a 1 Meg Volume Control, go to 500K or even 250K.
I dropped the 1 Meg Input Potentiometer to
500K, and it dropped the noise floor, 500K it is.
My Mullard 5-20 were built on discarded Leslie 147/122 "Rescue" Steel Chassis
they dulled by Hole Punches, and were difficult to
work with.
Thick gauge Steel is not friendly, and in 1996 this
was my first Tube Amp build.
These are in fact my very first hand made Tube Amps and took
years to perfect.
I learned so many things by iterating on these, they
were a School in Tubes
My layout screams Cary Audio
as
I used to enjoy their brochures in the 90's
also by reading lots of Stereophile when the magazines were the
size of a Readers Digest
Then I so loved the NeoClassic30 knobs, so I put them on the
5-20's, they match the Brass plates.
I have enjoyed these amps more than any other, and
have upgraded them
dozens of times. I have fried Tubes, Resistors and
Popped Capacitors.
Yet, now these are my true first DIY loves, an
almost 30 year relationship.
Cathode Bias, 20 Watts, Pure & Dynamic, fast and open
Ultra-Linear, Push-Pull 6.6K Primary
Designed by Engineers at MULLARD LTD. in 1959
A WORTHY DIY PROJECT TO CONSIDER, PHENOMENALLY MUSICAL
EXQUISITELY CLEAR
PRESENTATION, IF YOU WANT TO GO 'ALL THE WAY'
THEN CONSIDER SOWTER TRANSFORMERS
THESE AMPS HAVE GRACE, BUT ARE NOT POLITE, THEY ARE "IN-YOUR-FACE"
NOTE THAT KT-77's WILL PUSH THE SOUNDSTAGE BACK A BIT WITH SMOOTHER
SOUND
IF I GET ENOUGH INTEREST, I WOULD PROBABLY HAVE THE MULLARD CHASSIS
BUILT AND
MACHINED WHILE ALSO USING SOWTER OUTPUT TRANSFORMERS.
THIS WOULD BE MY FIRST COMMERCIALLY AVAILABLE AMPLIFIER.
MY TAKE ON
CLASSIC TUBE AMP HYPERTENSION
"Un-Regulated" DC Power Supplies on most Classic
Tube Amps built in 1950's and 60's and earlier
These Power Supplies do not work as well today
When you home voltage climbs past 120VAC
Now for the practical explanation that anyone can relate to...
HOW CAN YOU TELL
THAT YOUR TUBE AMP IS SUFFERING
FROM POWER SUPPLY HYPERTENSION?
VERY LITTLE, OR NO DEEP BASS
EDGY SHOUTY MIDRANGE
STRAINED UPPER FREQUENCIES
LISTENER FATIGUE
AUDIBLE
BUZZING AT YOUR CHAIR
POWER
TUBE FILAMENTS LIGHT UP A DARK ROOM
THE PLATE/FILAMENT TRANSFORMER OPERATES VERY, VERY HOT
YOU CAN FEEL THE TRANSFORMER VIBRATE
YOU CANNOT HOLD YOUR HAND ON THE POWER TRANSFORMER
Now read on....... and enjoy valuable Tube Saving insights
Not a keyboard jockey, but a real Engineer.
Electrical Engineering Degree 1986
Professional Engineering license, PE. 2004
FCC General Radiotelephone with Ship Radar Endorsement
Member of IEEE since 1982
Amateur Radio Extra Class since 1988
I am not an influencer
I actually make things happen
110 VAC, 115 VAC, 117 VAC, 120 VAC, 125 VAC
What is the insight here?
Residential AC Power has changed, as the years
have passed us by
We live today in a Solid State Modern Electronics Age.
Power Supplies are now Primary Voltage agnostic
they all (and I mean 95%) have
some form of DC Voltage Regulation.
By implementing DC Voltage Regulation the DC Power Supply is primary agnostic.
Power supplies today are pretty much agnostic, to the Primary AC Mains at your Home
receptacles.
When that piece of equipment, is connected to 120 VAC
the DC supply
regulator produces a
steady 15 VDC.
When connected to 115 VAC the Power Supply still produces a steady 15 VDC
When connected to 117 VAC, you still get 15 VDC.
And when the Mains rises to 125 VAC, you still get 15 VDC.
If the primary voltage goes above 130VAC, the MOV will fire and the fuse will
blow
This is called :DC Voltage Regulation:
But thus is also absent in 97% absent from Classic Tube Preamps and Tube Power
Amp
Power Supplies.
Some Classic Amps like a Grommes 260, used a Gas Regulator Tube to regulate the
Screen Supply.
So when the AC Voltage feeding the Primary of your Tube Amp increases past the
design specification
of the Primary Voltage tested at Full Load on the Secondaries, the AC and DC
voltages rise and fall.
Hence there is no :Regulation:
If the AC Mains voltage rises to 125 VAC; a regulator would control this, and
produce 15 VDC
as in my previous example.
But regulators have a lower limit and when the AC voltage drops down below this lower limit
the regulator stops wlorking, and the electronic device it is powering will
stop working.
When a
Voltage Regulator circuit is not getting enough Voltage to be able to regulate
it.
or if the Regulator gets too much DC Voltage, it can burn out, there are upper
and lower limits.
Have you ever had a brown-out at home when the AC Mains drops?
Your Solid State Electronics will stop working while your Incandescent Lamps
dim.
This is exactly the analogue to your Tube Amp, the amps in effect Dim out until
the Music sounds crappy.
Just as well, if there is a excess current draw, same, the Regulator can fail
when the AC Voltage rises past 130 VAC
of the Metal Oxide Varistor will fiire and short, protecting the equipment from
burn out.
The MOV commits electrical Hara-Kiri all in the name of blowing the Fuse.
With Classic Tube Amps, this does not happen, but if you drop the AC Mains let's
say below
110 VAC, you will starve the Tubes and it will sound "wonky", until you drop
down to 90VAC or less
it will start to sound raspy and distorted.
If the Classic Amp is connected to 130 VAC, it will slowly burn out and this is
a fire hazard as the
mains Fuse may not work in time. This is the part where some people refuse to
swap out their 60 year
old Power Supply Capacitors, melting the Power Transformer Secondary while the
Fuse does not blow.
Tragic ending to a system of beliefs in keeping old amps 100% stock.
Every belief system carries a price to pay.
UN-REGULATED DC POWER SUPPLIES
With newer Tube amps from the mid to late 1970's, no worries.
Boosted DC is generally not a factor on late 1970's Tube Amps, but there are
exceptions.
Some 1970's amps may operate their best on
117 VAC, with 120VAC the upper limit
Tube Amps made prior to 1969..... well they don't typically operate well at 123-125 VAC.
A Tube Amp fact: Tube Amps are designed to operate with their Un-Regulated AC
and DC
Voltages.
When the Mains goes up, so do the DC Voltages.
When the mains drops, the DC Voltages drop as well.
But the Tube Amp keeps working until the AC voltage drops below a lower limit,
and the amp sounds fuzzy.
or the AC Voltage rises above an upper limit, creating electrical stress on the
Tubes and Components.
Boosted DC and Filaments is all a case by case thing.
So when in doubt, measure your AC/DC Voltages, you might be
surprised or not, depends on the values that you measure.
Note that DC Voltages 10% different from nominal are usually OK
Filaments, they should always be connected to AC/DC voltages within 5% of
published spec.
Finally manufacturers have always cut corners for profit
so Mains Transformers could be victims of the "less capacity" for
less price, meaning a Hotter operating Mains Transformer with little
or no headroom for current delivery capacity.
FILAMENTS EXAMPLE:
I have a good proven Tube amp schematic that I want to build from scratch.
"Never use schematics that were never actually built and tested, I learned the
hard way"
Stereo Tube amp uses four EL34, two 6SN7 and two 12AU7, with a 5V Tube Rectifier
The 6.3V filament currenty draw will be calculated as:
[(1.5A) x 4] + [(0.6A) x 2] + [(0.3A) x 2] = Total Filament Current Load
(6A) + (1.2A) + (0.6A) = 7.8A
So the correct sizing for this filament load is 8 amps as it is unlikely
to find a 6.3VAC, 7.8Ampere Transformer.
The usual "more is better" does not work here, as the filament voltages are
almost always "Un-Regulated"
So you need to have a Filament Voltage that is +/- 5% of 6.3V.
If you use a much larger Transformer capacity, the AC Filament Voltage will not
settle
at 6.3 VAC, that is not how Transformers work.
Transformer Specifications have a N.L. (No Load) & F.L. (Full Load)
What you want is to look at: the Full Load Current and size your Transformer for
exactly that.
Headroom on Filaments is not cool, Headroom is beneficial for the High
Voltage
Winding of the Power Transformer. Here one really wants to use a Transformer
with enough capacity to operate at 70% to 80% of Max HV Load.
Straining a Power Transformer does not usually make a good sounding amp...
usually get buzzing and hum.
RECTIFIER TUBE:
This is easy: 5AR4/GZ34 so that one will use a 5V/2A Filament Winding.
Here the good design practice is the same as 6.3VAC, design the load to match
the winding capacity. So the answer here is simple.
Tube Rectifier Tube Filaments are best connected to the exact same Transformer
Current Capacity so if you have two 5AR4 in Parallel, that would be 5V,4Amps.
You really can use a 5 Volt, 5Amp transformer, but that is about the limit.
When you over dimension a Filament Transformer section, you will have boosted
Filament voltages
and these can be damaging to Tubes, not the Transformer.
I read a book published in the late 1930;s that provided empirical data in
shortened tube life
when Filaments are fed by a voltage more than 10% above spec.
On the other hand "under-dimensioning" can lead to long term Transformer damage.
The rule is to always design your Filaments to match the Transformer winding
for 6.3V, 12.6V and 5V which are 95% of the voltages we deal with on Filaments.
HIGH VOLTAGE:
The High Voltage section, you can add some Headroom here and compensate
with Choke DCR and the correct Voltage Dropping Resistors.
In fact the amps that I build always start with the Power Supply Design.
If our Stereo Tube Amp needs 350 Volts DC at 230 milliamps we need to
look for a Power Transformer with 375-0-375VAC at 250 milliamps.
It is much easier to drop a few tens of volts by using a 375V Center Tapped
Section
with 20 milliamps headroom, maybe even 30 milliamps.
It is never wise to use a HV Section that is exactly the full load value
as this will eventually burn out the HV Transformer Section.
The best way I know on how to introduce the correct value Choke and Voltage
Dropping Resistors
is to experiment with power resistors and empirically load the Transformer so
that
when connected to 120 VAC the Amplifier Voltages measured are within 5% of
nominal.
WHY?
All of the Amplifiers that I have built, all of them do noty require a VARIAC,
these amp
can all be plugged into 120-125VAC and work very well.
So the goal here is to build Tube Amps that do not require any Voltage Control
and can universally connect to any mains voltage between 117-123 VAC.
CONCLUSION and PREFACE....
Just because the rear panel of your 1959 Tube Amp claims that it can connect
to 125 VAC, believe me, this is usually not the case.
SO WHEN WE THINK ABOUT POWER?
Also when you look at the back of an old Tube Amplifier and read 117 VAC, 200
Watts.
This does not mean 200 Watts of Audio Power!
This means that 200 Watts of AC Power are consumed when operating the amplifier.
P = V * I
200W = 120V * I
I = 200W/120V = 1.67 amps
So the Fuse to protect this amp will be a 2 Amp Fuse.
I really have never seen Audio Output Power indicated on the amplifier itself
but there are exceptions to the rule.
Audio Output Power specifications are usually in the Manuals or Datasheets.
Just enjoy the Music.
This page is a mix of my past, where I spent years of Bench Time at work, then learned by making many mistakes.
Here you can benefit from my real Classic Tube Amp experiences.
This page is about my Tube Amp journey and how I came to realize that some Classic Tube Amps
from the 50's, 60's and early 70's
might have a hidden disease
the slow & silent "Power Tube
Red Hot-Rod Zone"
I went on many "Deep Dives" on Vintage amps (for newer Tube
amps, just skip this page)
and noticed a pattern
with many of the older amps from the early to mid 60's when
you plug them into 123 VAC, they can run quite hotter than necessary.
It does not always happen, but one always has to look for the signs of
Amp stress and recognize it.
When I gathered my test sheets/restoration notes where I wrote down the various
voltages across the amps
on their respective schematics, I saw that for each one, there was a repeating theme.
my DC Voltmeter was whispering at me, but I was not paying the proper attention.
Neither was I looking at the Power Tubes, in a very dark room when they
were operating
when I was new to the Tube Hobby, who knew, I was into Tubes and had no
real experience?
After 2 years, 1996-1997 I realized what was happening, as I saw Power Tube
Plates Red quite quickly indeed
when I put the light out at night. The dark ember glow of Red Plates....
OMG!
A few Doctors describe their discovered diseases, by their own names.
But I was not going to call this anything with my name, just call it
what it is,
Quads of expensive EL34 matched tubes, kept piling-up on me, way too
soon
And the Power Tubes would actually make noises as they warmed-up and
cooled down
Like small tingling sounds, such as softly tapping on a Wine Glass with
a metal object.
One Caveat;
if your Home Mains is always 120V or less, say 117-119 disregard this
topic altogether
You should always check ANY Power Tubes in a dark room to look for Red
Plates.
This applies for Homes that have AC voltages greater than 120VAC most or
all of the time.
There is a reason why some Homes will consistently have 123-125 VAC from
the Outlets.
The reasons why are the subject of a more interesting but separate
subject.
LAYMANS EXPLANATION
Power Company Sending End & Receiving End Voltages
In electricity, Power is Generated and also Power is Lost.
Like the efficiency of a Car Motor, only a % of the Heat/Power/Torque
Generated
goes to the Drivetrain. Same for Electrical Power Distribution.
The higher the sending end Voltage, the less power is lost across the
transmission lines.
Simple Plost = I2 x R
As you increase the Voltage, the losses across the transmission line
decrease as the
square of the Current. The Line resistances are steady, so by lowering the
current you lose less power to heat.
But lowering the current means boosting the voltage to keep the Power
constant.
Hence, Tube Amps that use un-regulated
power supplies can be, (and I caveat this) affected by the Voltage Boost.
Especially Power Transformers with Primary Voltages in the 115VAC Range,
wound to meet a standard
that was once okay, but take that amplifier from the late 50's or mid 60's,
plug that into
125VAC and you will measure BOOSTED voltages on the DC and also the AC
Filaments.
Hence like High Blood Pressure, it is the silent killer....
Note: The only sounds Power and Rectifier Tubes should produce, are out of your
Speakers!
If the tubes make noises when warming-up or cooling down, you probably have
an issue with the Amplifier.
Vintage Classic Tube Amplifier
"Hypertension Syndrome"
This is the silent
Tube Killer,
but why Sherman, why do you say this and most Audio Forums disagree?
Why do people come at you with hate and derision when you try to explain
Science?
A Wise Man once stated "Ignorance is daring"....
Answer: my Pro-Bono Webpages are my refuge. I am a
Science refugee and avoid the world of beliefs and hobby dogma.
I
treat all subjects with
tons of detail, and mathematical fact. Even at my job I am responsible for
minute technical details that can have a catastrophic result if glossed-over.
But again, as I think this is very
important to the Vintage Tube Amp Equipment enthusiast (especially on old Tube Power Amps), I will go
into electrical jargon, a language that is like learning a new roadmap.
While most of the folks on Audio Forums have
great interest, but no
idea or 'feel' for what is happening inside their old
amps, I hope this will help them understand why their power tubes seem not to
last more than a few month's.
So what I am
to explain here, relates to all of the precious ST-70's,
ST-35's, Mk4's and Mk3 Dynaco's, Scott's, Fisher's,
EICOS's, Marantz's, Pioneer's, Sansui's, Kenwood's, Grundig's, McIntosh,
Luxman's. etc.
Any old 1950's to 1970's Tube Amp may have Hypertension.
When Paleo-Tube units are suddenly transported
from 1960 to >> 2021, and operated in "their an all original condition", they are being plugged into an electrical socket that
is often (not always) much too high in AC mains voltage.
The old days of no Internet and no Cell
Phones, Carbon Paper,Typewriters, Ditto Machines
Those days are long gone.... (RIP), but back is the Inflation of the early
70's, :( bahhhh.
Our
power grid today often measures greater than 120 VAC RMS, and this can lead to
slowly frying
out old Tube Amps, and also over heating power transformers
and sending filaments into over-voltage.
If you are one of the lucky who have 115-120V at your
home, you can stop reading this, your old Tube Amps will dom just fine.
This syndrome is focused on homes whose electrical mains in the US, territories
and possessions never drop below 120VAC and often measure 123-125 VAC, here is
where old Tube amps start to sweat.
I think my worst ever case of
hypertension was the pair of Stromberg Carlson AR-411, at 121
VAC those amps would immediately boost their DC to almost 430 DC
volts and they were not intended for more than 370 volts DC. The Power
Transformer primary was wound for 115VAC and the transformer current delivery
capacity was close to Imax.
The confusion that sets in when a bottom cover is pulled off and one is just
staring at all those parts, who can blame people for not understanding.
Hey even Eddie VanHalen (RIP), knew about Tube amps and Variacs.... Eddie got
that Brown-Sound using a VARIAC to lower the
AC Voltage on his Tube Amps.
I think that there is no single Hobby that has so many interesting people, yet
many totally confused by
Electrical Theory and imagining things that do not exist.
People still say, write and believe that there exists 110VAC, this is ancient history folks.
The last time 110VAC was
coming out of a US outlet was probably 1950 or earlier.
Not even the Motorcycle and Auto restoration folks, get into
so many bizarre and unique conversations on Forums,
A Brake Pad is just
that a Brake Pad, a Sway bar is just that a Sway Bar, and those that claim magic
are immediately called out on the BS.
But, in the Electrical realm, people come up with
some really creative thoughts, not so much Science, but lots of weird
misconceptions and ensuing arguments.
You never read about someone saying that Rice Paper Tubing for
Brake
Lines makes Braking better, you can actually feel the brake pedal more?
And when things really get strange, Room Treatments and all of the things to
make a music room sound better with your equipment.
One Shaman was selling Battery
Powered Clocks to improve the Sound in a music room (Machina Dynamica
fraudsters on Audiogon).
This is just too
bizarre for me. Room treatments are absolutely essential, when done right.
Yet this stay-at-home hobby is good for keeping feral Men from Bars
and the stray things Wives just hate, maybe that Pot Smoking friend, who always
shows up Stoned :)
But you do have people claiming so much stuff on Audio Forums, that is borders
on the George Carlin insanity evel.
Insanity mixed with a touch of
righteousness, just the right medicine for a soldering session on a kilo buck
amp, just to upgrade a few special parts that make absolutely
NO SONIC DIFFERENCE
and have degraded the value of the Amplifier and make absolutely ZERO sonic
improvement.
Replacing old functional Screw Terminal Speaker interfaces for plastic 5-way
binding posts, with zero sonic improvement or difference, but the Amplifier just
lost value.
I am for Amp Molestation, but not doing stuff that makes no sense. Also people
insist on replacing perfectly good RCA Female Jacks (Receptacles), so unless the
RCA Receptacle is damaged, rusty or fails to make contact with the RCA Plug
Center Pin, leave it alone. Drilling larger holes on Classic Amps for new
interfaces is like drilling you 1965 Corvette to accept a fancy new Side View
Mirror.
If it is not broken, please leave
it alone. The difference between a $1.00 Capacitor and a $100 Capacitor often
requires a $5000 amplifier to be able to hear a difference, enough to warrant a
change.
I come from the School of, "If it is not broken, don't fix it"
This
Sherman learned the hard way, years of Electrical Engineering examinations,
literally thousands of hand Calculations and I graduated before students even had Laptops.
Then years on a Workbench at Motorola and GE, soldering, Oscilloscopes, Signal
Generators, RF Millivoltmeters, Simpson's, Flukes, Microntas, Network Analyzers,
ANRITSU Site Masters....
I used the very first 5-1/4" floppies at Motorola just as I walked out into a
Kraftwerk-like World, full of computers and big hair, the 80's was full out. The
Music scene was an explosion of modern synth and electronica both European but
Global. This seems to coincide with the term World Music.
The Summer of 1986 and the eighties
with MTV were on our SHARP
Transistor Color TV. People
in the 70's even built Color TV's from Heathkits, I found that quite extreme even in the
70's and 80's. even back then I thought that people who wanted to build their
own Color TV's were nuts....
So yes, I did code my TI-58C to pass my Chemistry examinations, I put all of the
Alkaline and Acid formulas for Ph, kPa, etc. on my TI, worked well that
TI, but the HP-41 was a much better Calculator with RPN notation.
So what I am sharing here, I hope does
help other Old really the older generation of Tube Amps from the late 50's to
early to mid 60's. Usually Tube Amps made in the 80's onwards are just
fine. I am referring to older style Fishers, Scotts, Dynacos.... Knight, Olson,
McIntosh, etc.
Tube Amps matter, and there are 33+ years of reasons why I think what we do to improve old tube
amps is important for the love of using classic electronics in this New Age.
Not just only for safety, but for the sake of
Hiogh Fidelity, and here is my story on this
silent killer; Vintage Tube Amp Hypertension.
A PRIMER ON RESIDENTIAL POWER & HOW IT RELATES TO VINTAGE TUBE EQUIPMENT
Maybe on a Hot Summer Day, when the Power Grid is totally loaded
with thousands HVAC's units cranking out Cold in your neighborhood
homes, our AC Power may
just dip way down to 115 VAC RMS, maybe less at 117 VAC MAX in an extreme heat case of 100F
degree days. That is a great stable power grid.
But I lived on an Island that had a electrical distribution that was old when I
was young, now it is older... much older. Fragile is the word, the Grid is so
old and over stressed, the investment required to modernize it are quite high.
Without revenues, and so on. So its a tough place with 124 VAC on colder days
and 122 on warmer days. Sometimes up to 125.6VAC RMS.
So here is that concept needs to be explained on how Voltage
rises and falls when a Circuit loads and unloads like a Transformer, on the "Un-Regulated Power
Supply", and this fact is the underlying corrective action needed to ease Tube
Amp Hypertension Syndrome. Old Tube Power Supplies don't have regulation. So
without it, the DC Voltage of the secondary side of the Transformer will rise,
accordingly. The problem comes when the Power Transformer is not dimensioned
with any "headroom" in the Power Delivery Department. So this means that when
the primary goes from the 120 VAC or even 115VAC that seems to still be a
standard in the primary windings along with 125VAC, my favorite tap!
Some transformer designs are inherently "passive" regulatiors with
little headroom. Once a secondary winding current capacity is at nominal, any
other winding that settles at an above nominal current draw. This is the effect
of not having sufficient loading on a Power Transformer Secondary. The trick is
to wind the Power Transformer with 20% extra capacity and with a dual primary
117 VAC and 125 VAC, but currently what is used is 115/125VAC vs. 117/125VAC
designs, with dual taps on the primary to switch voltages. This is the best way
to permanently treat the patient. But this is not always practical to substitute
the original transformers. Therefore the only and best solution is to set the
Primary Voltage with some type of Box.
Well you can make one easily if you are handy with electrical Boxes. You just
get a AC Toroid that has at least 800VA of Capacity and has a secondary that the
voltage is set to 55-0-55 VAC. This shaves just enough from the highish primary
voltages and steps the voltage down, by just a smidge like 5 Volts... and this
is perfect, and the Toroid will provide filtering and isolation from the AC
Mains.
Some traditional non-toroid are Ferroresonant by design,
so Transformers all have a max
and min loading specification, based on a primary voltage (look at the Hammond
Datasheet for FL = Full Load, NL = No Load) you get to know what the Full load
voltage is. If your filaments require 6.3VAC RMS @ 3A, then put a 6.3VAC RMS @
3A transformer winding (or section), or a discrete stand alone transformer to do
the job perfectly, and with better isolation. Individual Filament Transformers
also allow for better isolation to the High Voltages.
Most people think that a Transformer magically keeps and maintains the secondary
voltage independent of secondary loading, FALSE. A Transformer has a loading
curve and from this you know what the AC voltage is if you know the current
draw. The more current that that transformer section pulls, or loads, the AC
voltage across those windings will start to fall from a NO LOAD to a FULL LOAD.
It can look like a horizontal line on an X-Y graph. This is how you control
voltages, by not under or over loading the transformer. It is always best to
load each section near or at their designed maximum. There is no fear here as
when you properly load a power transformer secondary, the AC voltage developed
drops down, meaning that the DC Rectified Voltage is higher than normal. If this
boost is more than 5% some amps start to run HOT. While other amps seem fine
with a 20% boost over the primary AC Transformer Winding. The closer it is wound
to 120V the better, all the way down to 125VAC for Cathode Biased Amps that
always can use an adkustment when they are played on a mains higher or lower
than at your home. I like having a switch to flip between 115/125VAC.
When a circuit loads a transformer secondary, the secondary current rises rise
and the secondary voltage drops a bit, that is called regulation, and the range
is how it tries to regulate, but is actually a sloped load line.
This is different with Regulated Power supplies that have "Active Regulation
Elements" after the Rectifier does the job of converting 60/50 Hz AC to
pulsating 120/100 Hz DC. The DC Voltage on a regulated supply is ROCK SOLID
until the regulator capacity is exploded and the regulator shorts out.
Regulators come in 6.3V, 12V, 24V, 48V, 100V, 200V, etc.
The regulated power supply uses external components (regulators) to maintain
a steady DC voltage, but this is a different design than used in Vintage Tube Amps,
except the Grommes that used a regulated Pentode mode Screen Voltage. It used a
Tube Regulator I think with a 6L6 or a Gas Regulator, I can't recall.
What I am describing here, is not an intuitive fact, but so many people are
unaware that their 1975 Dynaco ST-70 is suffering from 123-125 Volts on the Primary.
AC Transformers have two important specs out of many;
Full Load and No Load AC voltages.
Old (and still some New) Plate and Filament transformers were designed and wound for an
AC primary
mains voltage standard of 115VAC or 117VAC.
So when you have one of these, you need to compensate on
the secondary of the transformer, to control the
rectified DC voltage to the target value. Just as well
the ASC Filament voltages can be higher than 10% over
nominal, and tubes can wear our at a faster rate when
they are powered with jacked-up filament voltage
People, the 120VAC Primary Standard (if there was ever
one) wasn't any part of
any manufacturer until maybe the mid to late 90's.
And people today still say "110VAC" and "220 VAC".... this is so
passé.
Folks, the last time AC voltage measured 110VAC
was probably when Frank Sinatra was alive and well in
his early career and homes lacked Safety Grounds or
Polarization HOT and RETURN orientation on their AC
outlets and plugs.
So when you
just plug a Vintage Tube Amp Power Transformer Primary to 120VAC - 125 VAC RMS,
the secondary voltages are almost always, immediately higher, and sometimes
dramatically higher.
The old Power Transformer will heat up, and
stress out, and the tubes, to the point where the equipment
can run super hot and the plates on the power tubes
start to glow red. Sometimes you can feel a slight physical vibration from the stress
on the Power Transformer.
The filaments can look more like light bulbs than the
deep orange glow.
Now there are exceptions, but
believe me, 8/10 old amps that have been on my workbench
break out into a hard sweat when connected to 120 VAC.
And being
the "tube-whisperer" I am, I
can see and feel the pain, just by visual and audible inspection.
I can tell
when an old amp is struggling, and can hear it in the
way it plays music. I will measure the DC voltage on the
first power supply capacitor and like a Doctor taking your Blood Pressure, I can
tell if there is trouble ahead.
Stressed-out Tube Amps and Preamps lack
"air", they can sound mechanical, lifeless, dry and often
stiff.
There can also be 120Hz ripple Buzzzzz on the speakers a
few decibels higher than you would like as the Power Transformer is delivering
more voltage than needed.
I know descriptions of sound are weird, but this
is the best I can to convey audio into words.
Basic
Transformer Formula #1
'subscripts' [p = primary], [s = secondary]
Vp/Vs = Is/Ip
Vp= Primary Voltage
Vs = Secondary Voltage
Is = Secondary Current
Ip = Primary Current
Here we have the most basic of Transformer formulas, it describes an "inverse" relationship between
Voltage and Current.
The primary and the secondary AC
voltages through a Power Transformer always have an
inverse relationship
between their Voltages and Currents.
And
in case you did not realize, and many folks do not, Transformers do not work with DC, Transformers work
only with AC.
Why, just pick up a book, Google it and start to read.
Read about Nikola Tesla, Westinghouse...
When
a reporter asked Elon Musk on how He learned about Rocket Science; Elon
responded "I read alot of books"
The only slight twist in the application of
magnetic inductance and reluctance are power supply DC smoothing Inductors (a.k.a. Chokes).
Inductors pass DC current while "choking" or smoothing out rectifier AC 120Hz ripple.
This is the Law
of Superposition, one of the most basic concepts in understanding circuits, look
it up, it explains lots of things.
So in simple layman's terms,
the way that a Transformer operates, it converts smaller voltages into higher
voltages, and vice-versa, and the same for currents.
That is why they are called Transformers, they TRANSFORM
VOLTAGES AND CURRENTS.
Another very important learning item is to beat the heck
out of Voltage and Current theory and really understand each one to the point where
you can take a White Board and explain them.
So with
Transformers, we have a combination of voltages and
currents flowing in the Primary and the Secondary.
The convention is that the Primary is the side that connects to the AC socket,
and the Secondary is the side that connects to your Power Supply Rectifier, and
Tube Filaments.
This formula, when applied, produces the
results that explain how Vintage Tube Amp Hypertension comes into being.
Just do some basic math, enter three out of the four variables and
solve for the missing one. Then after writing these values down, increase the
primary Voltage from 120VAC to 123.5 VAC and calculate the AC voltage on the
High Voltage Winding and also the Filament Windings, bingo, you just have the
first concept of how a Transformer "transforms" Voltage and Current.
Now with a Vp of 120VAC,
as in a modern Tube Amp Transformer, Secondary HV Voltages are typically higher, per design
and the Filaments are orders of magnitude lower.
Just as a practical example "Solid State" Amps go the other way, these
amps use Secondary
Vs. Voltages in the 20 to 60 Volt range, even as high as 100Volts. Transistors rarely need
very high DC voltages across their
P-N-P, N-P-N, or N/P doped Source to Drain Silicon of FETS and MOSFETS.
So when we increase primary AC voltage into an un-regulated
and rectified AC to DC Power Supply, this creates a permanent "BOOST" and is always measurable on the Secondary, and often, this is not good news
for the Amp and the Tubes.
The solution to this problem
is simple, but almost none of the classic manufacturers did this simple fix,
just wind the Power Transformer primary for the "worst-case" primary voltage of
125 VAC.
This way the equipment can be plugged into any duplex
outlet and be happy.
This is how I DESIGN all of my equipment and power
supplies. I baseline the operation on the worst case scenario.
Then I compensate when I have a Plate and Filament
Transformer that has a 115/117 VAC primary, so that the rest of the circuits can
work when slammed with 125 VAC. It can be done, it just takes some extra math
and empirical testing to "park" the Un-Regulated Power Supply in the "neutral
zone", Spock states: This is logical.
The exception here, is when the
Output of the Rectifier is connected to a filtered input of a Regulator Circuit.
The AC wall voltage can go up and down quite a bit, while the Regulator Circuit
keeps the DC output rock-steady.
BUT 98% of old Tube Amps
do not have DC Regulation. In rare cases as in the Grommes and Leslies, the Pentode
Screen voltage is regulated through a Gas Regulator Tube, this lowers distortion, and is
a cool thing.
Look it up, I think the amp is a Grommes 260
and the Leslies are the 122/147 Models, they use Tube Gas regulators.
Now about wire gauge.
The "gauge" or the wire
thickness of Plate and Filament Transformers for Tube
Amps, is usually made of Primary wires that are "thinner"
and
Secondary
Filament wires that are "thicker", generally speaking.
The High Voltage section is typically thin wire.
Practical example: How do
you think Power Companies send massive amounts of MVA Power through those
Short, Medium or Long Power Transmission Lines that cross our lands.
The power company generates AC voltage at
approx. 12.5 Kilovolts (Nuclear, Coal, Oil, Hydro, etc.) by spinning turbine generators.
Then they rely on
huge massive Power Transformers to "Boost" the Sending End Voltage to
basically "Lower the Current" across the Transmission System.
Hey our Transformer formula in action again!
This is how
you pay for Power, you receive over the wires that are no thicker than your arm,
that carry 250 Kilovolts, then get stepped-down to the split-phase 240 Volts AC
that then splits out in your ASC breaker panel into two 120VAC rails. This is
another great subject to learn about. How to properly understand the role of
each wire that connects to your Duplex Outlet. You would be amazed at how many
people will take a Vintage Tube amp, damage the unit by installing an IEC socket
and then connecting the Safety Ground to the chassis.
Historical note: AC vs. DC was a huge fight between
Edison (DC) and Tesla/Westinghouse (AC). Edison preached DC Power Transmission, Tesla was
a fan of AC Power Transmission, and we all know who won that battle. The reasons
why are key to understanding Electricity and knowing cool things.
Now, we will discuss the Filament windings, then the High Voltage windings (often
called Sections).
The typical Tube Amp Power Transformer
has a HV Section from 200 to 800 Volts (it can be 2 wire or 3 wire known as
Center Tapped) AC, 6.3 Volts AC (also 2 or 3 wires), and 5 Volts AC (same, these
can also have a third wire).
The center tap wire on a 6.3 VAC filament section is of
great benefit for Tube Amps and Preamps. It allows the 6.3 and or 12.6 VAC
Filament Section to be connected to DC Ground. This allows the reduction of
Common Mode noise and also, if necessary allows a simple means to "float the
filaments" with DC voltage on Totem Pole Tube Gain Circuits. This is yet another
little piece of knowledge, remember the Law of Superposition? Hard at work again
here. Look it up, it is a cool piece of information.
Manufacturers
also make have some different sections if they design for DC on the tube
filaments, and this is more common on Tube Preamps, to have a 12.6 Volt AC
section, or maybe a 20VAC section (as in the Scott LC-21). These can be
rectified and produce DC for the Preamp Tube Filaments, it lowers noise. But...
at the price or the polarization of the filaments, causing them to wear out 10%
faster. This is another curious aspect of Tube Filaments operating on DC current.
Look it up, another small piece of Tube wisdom. A philosopher once said "seek
and you shall find", in my Spanish "el que busca, encuentra".
Enough on Filaments, only to close this out by stating
that you want to avoid over dimensioning Tube Filament Transformer sections.
If you need 3 amps of AC filament current at 6.3 VAC, get a 3 ampere, 6.3 VAC
section. Headroom works against parking your tubes at the proper quiescent AC
filament voltage. If you believe that a 6 ampere, 6.3 VAC filament section will
work better with a 3 ampere load, think again. This is a very important DIY tip
that took me years to learn through the school of hard-knocks!
Now lets talk about the High Voltage part, that is probably where most of the
Hypertension issues manifest themselves.
The HV DC current (milliamperes of AC) are produced from across the High Voltage Plate Winding section on the secondary
and will almost
always have somewhat thin wires, as the gauges required for 250
to 500 Volts AC at milliamps of current are thinner than
Filament wires, and usually the case rather than the exception. Unless the Secondary HV winding is
providing more than 350 milliamps or greater, unusual
for any
Tube Amp, save for the Dynaco MK6 with defunct 8417
Power Tubes R.I.P.
Now, we move on to winding ratios and
the formula, also important as it allows
one to determine an un-labeled Power Transformer winding ratio, and
also the impedances of any "mystery"
Output transformer, such as a rare Output Transformer
with "no labeling" that you are salivating to use on a DIY
application. Output Transformers are the most critical component in a Push Pull
Transformer Coupled amp, but that is a subject I discuss in other parts of my
website.
Basic
Transformer Formula #2
Vp/Vs = N1/N2
Where V = Voltage, N = Turns
Note: A "Turn" is
counted as one 360 degree winding across a laminated
transformer or toroid magnetic core.
We also have an impedance "version" of this type of formula that allows one to use a Sine Wave Signal Generator,
plus an
Oscilloscope, to empirically work-out
the "Primary and Secondary" impedances of Output Transformers when they are not
published or labeled. The Power Rating is calculated from the size of the core
itself, that is more involved, and I will not go into that interesting tangent.
Basic
Transformer Formula #3
(Vp/Vs)2=(Np/Ns)2=Zp/Zs
But I
diverge here, as an Electrical Engineer I have these formulas burned into my
mind, after all, 35 years of Engineering does that, it makes us Geeks start from the basics
in College, and then, apply the heck out of these in the real world.
The Tube Whisperer believes that any Wise man,
armed with the knowledge of Mathematics, can always understand Matter, Space and
Time through Science.
Now we discuss the High Voltage secondary Power Transformer section further and
how this can get boosted and hurt your Tubes.
In most Tube Amp
Power transformers, the secondary HV plate
winding voltages are greater than the
primary voltage, or equal to (e.g.. maybe for voltage doubler
applications?) look this up, there are also ways to
triple the voltages. The penalty is that it halves or thirds the current
capacity...
Hence and this is all a mathematical thing, when you
take a ratio of Primary to Secondary windings and work
some numbers, the design center voltages on a Power
Transformer will have two values given;
No
Load = the resulting AC voltage measured when the
transformer section is not connected to anything.
Full Load = the resulting AC voltage measured when the
transformer section is delivering the full rated current.
I previously stated that the key to good and safe
"Un-regulated" Tube Power
Supply design, is to always load Tube Filaments @ no less than 80% of the Full Load
Current rating, or ideally,
at the published Full Load specification. DIY tip!
This is a Audio Rodent belief that if you
use a 6 amp Transformer on a 1 amp Filament Load is better.
Here the unlikely reality that goes against the "tweaker mentality" and gets
well meaning DIY enthusiasts into Tube Hypertension, if you paid for 3 amps AC, you
need to use the 3 amps AC. More here, is never better for Tube Filaments.
Now this is not the case on the High Voltage section, here we need to
consider 'headroom' as part of the normal load and operation, this goes with the
Tweaker Mentality, part of the laws of chance and assumptions.
Now loading a HV
AC Transformer secondary to 100% will result is a Power Supply that does not sound good, there
is no margin, and the DC High Voltage will experience sags. Voltage sagging is something we want to
avoid in HiFi Tube Amps, but may be a interesting "tone-affecting" feature in a
Tube Guitar/Bass amp.
The HV section
that creates the 200 to 525 Volts DC after it is rectified, is usually happy at
65 to 75% of full load. It is never a wise design and load the HV High Voltage
Transformer Section at full load, this means Heat, Trouble and Voltage Sag.
Again the High Voltage section requires "headroom" to properly give your amplifier or
preamplifier the necessary steady state DC voltages that the tubes require and
keep the Power Transformer from overheating. Keeps the Plate Voltages steady
from wandering when the tubes crank up Also Sprach Zarathustra!!
Now if
you end up with too much DC voltage, you have either "over-dimensioned" the Power
Transformer Secondary HV section capacity, or need to drop some of the extra DC
volts across a DC Choke, or Power Resistor or both.
If you have to drop more than 30 to
50 Volts, you probably need to re-think your HV design. But I digress, as I am talking about
Tube Amp Design here, and I want to explain Tube Amp Hypertension, and this is not really about how to size a Power Transformer.
I am working on my first Tube Amp Book, to be published in 2022-2023 to take
people who want to get into building amps to the level they need to enjoy good
results.
My knowledge is so useful, to be able to follow what happens in Vintage Amps
operating at 125 VAC that I included this here as something good to know. When
you decide to build DIY, this is all critical information.
So..
about the Filaments again...
The AC
voltage to your precious and expensive NOS Telefunken or
Bugle Boy Tube Filaments, should settle near the 6.3VAC or
12.6VAC, and stay at or within a +/- 5% value, you are fine, and your $wallet$ is
safe.
This is quite straightforward for modern current
production units and almost always taken care of by the
designer.
But, on a Vintage Power Transformer, it
can, when a 115VAC Primary is connected to 120-125VAC
significantly boost all of the AC secondary voltages,
not only to the tube filaments, but the HV section as
well, causing overheating, super hot tubes, filaments
that look like small light bulbs, tubes making noises as
they heat-up into "over-heat" steady state.
These are all the tell-tale signs of discolored artwork lettering on Tubes.
If your tube amp filaments are providing illumination
to
a dark room, something is off and wrong.
Folks these are filaments, not Light Bulbs, although
they are very similar in their fundamental design.
When over-heated, some Power Tube lettering will change color from
Red to Orange.
As in JJ
Tube lettering, and I love how JJ's sound BTW, they are
probably the best value in tubes today.
The other acid test of Vintage Tube Amp
Hypertension diagnosis is
to allow your Vintage Tube Amplifier or Preamplifier a warm-up
time of 15 to 30 minutes.
Then, try to hold the palm of
your "bare hand" on the top of the Power Transformer.
If
you cannot hold your hand there for at least 10 seconds,
without pain, you
are killing your tubes and making the tube sellers very,
very happy people.
You are probably in that Frequent Buyer Program, funded
by Audio Forums and have a great solid "return
customer" profile and likely complaining that tubes just
don't last.
Not to even mention those tired and worn out
Electrolytic Capacitors that you just cannot get yourself to update as you fear
that your equipment will lose value, ridiculous indeed.
That expensive $45.00
Metal Can FP type Electrolytic replacement capacitor
that you cannot afford, and is sorely needed by that "Un-Molested" equipment.
We now have a safety situation of a 35 to 75 and even 80 year old Power Supply capacitor that is dry of
Electrolyte. And this Capacitor is now operating at or above it's maximum DC
voltage rating, and drawing DC current, and may blow a fuse,
if you are lucky. Any Metal Can cap should never get even the slightest
warm. If that Metal can cap is warm, it is leaking and drawing DC from the HV
Power supply.
Unbeknownst to most, there is also Vintage Equipment
"High Voltage
Electrolytic and Coupling Capacitor "current creep" that does melt Power Transformer Secondary HV
windings before any fuse will blow.
So make sure that you stop
belief systems, and break out a calculator and a notepad. Stop believing those
Forum rodents and shy away from EBay sellers who flaunt
the "Unmolested equipment" narrative, they are, literally, playing with
Fire.
Using "Un-Molested" Vintage Tube gear is a sure way to
accomplish and achieve failure, while never, ever enjoying the full sonic
potential of a 100% restored Vintage Amplifier or Preamplifier.
Imagine the Car restoration people driving their old cars with the most minimal
change, they would be driving an Un-Molested 57' Chevy, happy that the car is
all original except for the Battery. Then one day, the brakes fail and they
crash. Was the value of this vehicle different when restored? Absolutely.
But the Vintage Tube Amp hobby is full of delusion, and
the manifestation of this has a name, and this name is "Un-molested".
Old stuff sounds old, old
parts are beyond lifespan, and old solder connections can behave like Low
Pass Filters - (LPF), cutting off precious high frequencies, delivering that
vintage muddy, old, idiosyncratic tube sound that hundreds of Dynaco PAS users seem to
enjoy? I just really don't get this.
I can totally
understand paying for a 100% original PAS2/3 Preamplifier to put on a shelf and
not use it. To own as an antique, not to be operated. This is where
"Un-Molested" makes total sense. In museums and large collections of
non-operations electronics. This is a cool thing, just don't dare to plug them
in a turn them on.
Every time I see those EBay
photos of Vintage equipment, old capacitors, old carbon resistors and the Green
Selenium Rectifiers, I just shake my head. I just cannot understand how people
will pay $800 for an Un-Molested Preamp when a fully and lovingly restored unit
loses all value, no bids!
The bizarre world of belief and perception hard at work
for collectors and well meaning but confused buyers.
You cannot even start to believe me until
you actually take any 100% stock original amp and test it.
Yes, Test Equipment,
that inconvenient part of the perception game, that calls on fools at the worst
possible moments when smoke gets in your eyes, tube amp smoke that is, not the
song. Although it may happen simultaneously!
Ever wonder how that "Un-Molested" group of
Vintage Hi-Fi lovers, may never hear the full potential of their vintage gear, as
they lust after that fuzzy, soft, rolled-off sound. They even start to get used
to bad sound, and when they hear a
restored amp with new tubes, they claim it sounds "strident",
"bright", "like Solid State", well this is called
High Fidelity.
In the realm of "Un-Molested" Vintage Equipment we have
here the host of
pre-existing Vintage Tube Amp symptoms:
>Huge channel to channel imbalances, old Balance Controls are pretty much shot,
an old $1.00 part holding the music hostage to a belief.
>Really bad Volume controls that are way out, and I mean way off. The
resistive carbon wafers often measure 30% different. Just use a dual channel oscilloscope to compare Left/Right Channels, sobering
Oscilloscope traces.
>Huge differences in out of tolerance Capacitors and Resistors. The ignored Dynaco PAS
Channel Mode and Width Selector Switch. Here we lose 50% of the glory of the
PAS2/3. The Carbon Resistors can be tens of Kilo-ohms out, and these resistors
are critical in value, and work in tandem and collaboration with the
"Un-Obtainable" 750K PAS Balance Control. When these resistors measure
differently, the Dynaco will
not image and the channel separation is dramatically degraded.
>Then we have unhappy
audio session visitors, and people, just too polite to tell these owners that
the equipment sounds
like shit.
Now there is one "band-aid" solution to all of
what I state above, to lay out some hard cash for a high quality 10 ampere
VARIAC to operate your pristine old, un-molested Marantz 9's.
If you
really believe, that your Vintage Amps sound better left "un-molested", be my
guest, and feed it what it needs from a Variac, start at 110 to 115 VAC and enjoy the fuzz
and all of the Vintage Amp beliefs and update your Insurance Policy.
I will always issue challenges to the "Un-Molested" cult., always.
Dare them to connect their gear to a Signal Generator and an Oscilloscope, and
witness
what is really happening to the music.
When audio beliefs do not allow one to touch
anything, and keep Selenium rectifiers and Dry/Leaky Power Supply and Coupling capacitors that they hope
will "reform", then a VARIAC is the only
thing that can save your vintage pieces from reality, and your house from a Fire.
This
way, you can safely dial down the AC RMS voltage from your AC
wall outlet down to 115VAC or 117VAC and make your
vintage amp play, but never safer. Never, ever
leave any original un-molested vintage equipment alone, and powered up. Only get
up for the Bathroom or another Soda.
Now.. once your equipment gets the magic wand, you will immediately
notice that the amp gets better Bass, the noise floor
drops down, and the tubes don't make the noises of slow
death, the filaments glow with joy and that Tweeter hiss, is
now far less.
You will also note a drop in the pesky 120 Hz Power
supply buzz, it
drops down to where you actually need to put your ear up against the speakers.
You will NEVER EVER have a noise free Tube Amp. But you can lower the noise
floor to such levels that are imperceptible from your listening position (sofa
or favorite chair/beanbag).
But when
you don't upgrade your old gear, and connect it to
2021 AC Wall Voltages, your precious Tubes are living
with "Vintage Amp Hypertension Denial" their "voltage
pressures" are in the Yellow to
Red ranges and the current rises, taking out
what little life they had to start with.
If you take your RMS AC Voltmeter and carefully measure
the AC loaded voltage across the filaments, and expect
to read 6.3VAC, you may be shocked (no pun intended)
that your meter reads 7.5 to 8.0 Volts AC RMS.
One sure audible sign of overloaded filaments is, that loud musical passages
sound overwhelmingly HUGE.
As if someone is turning the Bass control to Max when the music goes to from
Mezzo Piano to Forte and back down, this is a non-linearity effect created when
there are more free electrons emitted by the filament being sucked up by the
plate when the music swings hard.
Filament voltage control is a critical ASPECT
of High Fidelity in Tube Audio Circuits. Ignore and just order more tubes... at
your own $$.
Also Vintage Amp Hypertension will increase DC voltages to the Power Supply Capacitor sections
and these can 20% to 30% higher, ouch.
Just read about that stock ST-70 FP Electrolytic Capacitor "first section" and
please understand it.
And never dare to power up a Vintage Amp with No Tubes in the sockets, the DC voltage
will be dramatically higher and unless your first capacitor is rated at 600
Volts DC.
Also never dare to feed a Tube Rectifier Power supply with anything less than
60% of the AC Mains Voltage, doing this will cut the life of the rectifier as
the 5V Filament is starved and the High Voltage is asking for electrons it does
not have available. The silence of the tubes..... the Whisperer listens.
This my readers, this is "Tube
Hypertension-101"
explained in my best Layman's terms for those who fear Calculators and Formulas,
or may have a case of "Vintage Equipment Nervosa".
These and many of the reasons why you keep having to replace tubes
every 3 to 6 months are laid bare and raw.
I am a Tube Whisperer, and do hear when any amp loses that "magic" and sounds
flat.
When Tubes die out and fade
away, or when brand new EL34's immediately get Red Plates right out of the box
they came out of, something is off.
This my
amigos, is the bane of the flat sound of new tubes in
un-molested vintage gear. And when you leave these cults, and become an
independent thinker, your High Fidelity experience will reach a new phase, a
bright sunny day, better sound and spending more money of source material,
better streaming sources and interesting tweaks for your music room.
So what can we do?
Well I am one who just will pull out
and replace,
if possible, the original old Power
Transformer and use a new one that can connect to
125VAC and not even break into a sweat. Or I can try to
modify the Power Supply, but with limited success.
If you
absolutely prefer to keep the Vintage Power Transformer wound with a 115/117VAC
primary, invest in a high quality Variac, or build yourself a Steroidal Balanced
Power Transformer Box. If you are on the cheap side, and I have nothing against
cheapskates, they also have rights, they can buy a Bucking Power Transformer box
on EBay to lower the Primary Voltage down to 117VAC.
Parking Tube Amps and Preamps for optimal operation at 125VAC is my
fundamental design criteria, then everything else falls into place!
This is especially true
for and of Cathode Biased Tube Amplifiers, as these have
no way to adjust the
current through the Power Tubes.
So what are the benefits of
a serious Vintage Amp upgrade?
>No transformer mechanical buzzing
>No overheating,
>None
of that "lost magic" as your tubes now Bias-up with no
fuss, and play well.
>Extra Cash, to help you score that nice
Bordeaux Red for your next music lovers session
>Primary voltage control to 115/117 VAC, saving your
tubes, and improving musicality.
After all this is why we
love tubes, they are imperfect musical devices, able to
make music in so many different ways, never twice the
same.
But Tubes do need care and feeding, else you just
replace tubes often and complain that Tube amps are too much of a hassle.
Tubes are like Orchids, they don't live long if you don't understand them.
BELOW ARE MY
PERSONAL DESIGN GOALS FOR UN-REGULATED TUBE
POWER SUPPLIES
The maximum AC Filament Voltages that I recommend should
never exceed (+/- 10%), so let's do some math so it
becomes clear what I am taking the effort to explain
here.
6.3 VAC RMS x 0.1 = 0.63 VAC
RMS
+Max Filament Voltage is 6.3 VAC RMS + 0.63 VAC RMS = 6.93 VAC RMS (Maximum AC Steady
State)
So... 7.0 Volts AC
RMS is the absolute "LIMIT" on any 6.3 VAC Tube
Filament, exceed at your peril $$.
-Min 6.3 VAC RMS - 0.63 VAC RMS = 5.67 VAC RMS (Minimum AC Steady
State)
-
At 6.0 Volts AC
RMS your tube life will extend by 20%
-
Less than 6 Volts and your tube will suffer from
sleeping sickness (more about this in 1960's Mainframe Computers and Tubes
that got sleeping sickness, a problem we
don't see since computers went Solid State).
I really suggest and prefer this
specification to be no more than (+/- 5%)
6.3 VAC RMS x 0.05 = 0.315
VAC RMS
+Max 6.3 VAC RMS + 0.315
VAC RMS = 6.615 VAC RMS (AC Steady State
Filament Voltage)
-Min 6.3 VAC RMS - 0.315
VAC RMS = 5.985 VAC RMS (AC Steady State
Filament Voltage)
So now that we get the mathematical results for the
Filaments, let's now examine what Vintage Power Transformer Tube Hypertension
does to your Plate Voltage with an actual Case Study.
How this has a dramatic effect on all Tubes, all Power
Supply Capacitors and Components, the Cathode Resistors and in general, the well
being of any Vintage Tube amplifier or Preamplifier (a.k.a Dynaco ST70, EICO,
Scott, Fisher,...... the list is very, very long) is sobering.
Let's make this one easy and
free of Math, I can explain the concept better using a
real amp.
SHERMANAUDIO CASE STUDY: THE DYNACO ST-35
"MANUFACTURED HYPERTENSION"
The first capacitor Section of the stock Dynaco
ST-35 amp has a published specification based on a
120VAC Voltage.
So you may say, what's the big deal, 120VAC, easy.
The
most I ever measure at home is 123.5 VAC, but this is where
the deception hides, so what's the problem Sherman,
explain this to me, are you obsessed?
I pull out of the Dynaco Manual a clip of the ST-35 DC Voltage Chart.
This chart
is referenced to 120VAC on the PA774 primary, and if your amp is
lucky, and your AC wall voltage is 118VAC or 120VAC and
below.
And even at 120VAC your friendly factory vintage Dynaco Power Transformer
PA774 is already sweating for one key issue, Dynaco
over-dimensioned the HV Secondary, but why?
I really don't know why, but have a
strong hunch it has to do with the 7189 Tube. I digress for a moment here about
the 7189.
When this Tube was unleashed on the market, it was
probably common for people to believe that a 7189 amplifier could use a
6BQ5/EL-84 as a substitute, wrong.
The truth is that an amp designed for 6BQ5/EL-84 can use
a 7189, but this is a one way street. If you have an amp designed for 7189, a
6BQ5/EL-84 will perish, and in ways that fried quite a few Output Transformers.
The Olson AM-224 is a case study of fried OPT's. I have two of them, one, has
fried OPT's, the other actually made it's way to me before someone put EL84's
into it.
So the ST-35 has the 7189 thing going and I suppose that original PA774 design was made
to take advantage of the 7189 tube, and make the EL84 suffer enough pain to wear
them out, but no quite kill them off immediately.
The manual makes NO MENTION of this, and I have
un-masked Dynaco here. So all of you ST-35 owners out there, take heed, you have
been Dynaco-ed!!
Now, make that PA774 primary voltage 123.5
VAC, a very common AC voltage that we have at homes across
our nation. Now remember that transformer
formula:
Well on the PA774, we are starting with a AC Secondary
of 330-0-330 VAC, and this was a voltage selection intended to push the limits
of the Maximum Plate Voltages of a standard EL-84/6BQ5, beyond the max, it was
really wound for 7189's. and I will
show why.
In reality, the Dynaco people
most likely wanted people to enjoy this precious design using
7189 Tubes, that were readily available in 1968, but
today if you need a 7189, you have to buy the Russian
version 6n14pEB or pay $100 each for real 7189's.
Warning: the 7189A is not a 7189,
it depends on how the tube socket was wired. The specs of the tubes are the
same, but the pinout is slightly different so check before plugging in. Some
manufacturers used the spare pins on a 7189 socket for solder tie points rare
but possible.
I highly recommend that any ST-35 owner
only use the Russian Tube, real EL84's just burn out too fast in the stock ST-35,
but
they do sound great as they pass away.
I have a small tube cemetery full of Mullard 5-20/EL34 and
ST-35/EL84,
and these are like spent Rifle Cartridges, when I was learning to shoot without knowledge
back in the year 1996-2005, a time of Tube learning, Red Plates, Motor boating and lots of
hard $lessons.
If we examine the ST-35 voltage chart
below, and look at the bottom line, these are, from Left to
Right the DC Voltages that should be measured with a
VTVM (high impedance tube voltmeter), else what your
trusty modern VOM will measure will likely be 5 volts
lower due to meter circuit loading.
Just look at the Plate Voltage on Pin #7, 370 Volts DC!!
Ouch. You need to subtract the Cathode Voltage from the Plate Measured voltage
to calculate the actual Plate Voltage. So 370V - 13.5V = 356.5 Volts DC if the
Dynaco ST-35 factory plate voltage value. Go to the EL-84 spec sheet, the Max
Plate Voltage for an EL84/6BQ5 is 300 Volts. Dynaco is parking the 6BQ5's at
356.5 Volts a whopping 56.5 Volts over the published specifications.
This to me screams 7189 all over the place, and why I
recommend using EL84M/7189 or the Russian 7189, makes sense, and holds up to the
punishment.
These voltages are proof that the ST-35 was not an EL-84
amp but a 7189 amp with an EL84 disguise.
The (3) three Power
Supply Capacitor HV voltages are suspect, and last one, is the Common Cathode Resistor
voltage reading on a stock ST-35 FP Capacitor, now unobtainable, 13.5 VDC, more
on this here...>>
If you take a stock ST-35, with
the Stock or even a New Dynakit PA774, and carefully with one hand
in your pocket, and the amp belly-up, with meter ground Lead clipped
to DC Ground, tell me what you measure?
My "Cover" ST-35 was measuring +420 VDC
on the first PSU Capacitor, yes folks not +380 VDC, so what was happening
here?
Well, for one, the secondary windings of the stock PA774
and the new replacement PA774's are wound to 120VAC and a ridiculous 330-0-330
VAC.
I am connected to 123 VAC, sound familiar, measure
familiar, Hypertension? Yes.
This is not a conspiracy to sell more tubes and lower
distortion, it is just bad Dynaco design, intended to push the bias on the Tubes
to achieve an unreasonable Power and Distortion specification, the Solid State
tube amp complex.
Dynaco seemed to
have been competing with Solid State, in the Tube heyday. So the solution was to crank up the voltages and currents
on the tubes, to compete with the "lower transistor distortion specifications",
happened in the best of families.
Yes
my friends, Hype is not modern, it creeps along the ages.
I am not sure why Dynaco wound
the HV secondary up to this extra 30 Volts AC per side,
but I have solved this problem. I replaced the PA774 by using a Hammond 272FX
with 300-0-300 VAC.
But will the 272FX fit the stock ST-35? Unlikely, Dynaco
chose to make this amp small, to give it Tube Amp Curb appeal.
I haven't one on hand to try, heck I may ask Hammond to make one that fits....
(a future Transformer Project in the backburner).
I even asked one of the PA774 sellers, if I could order
a PA774
with a 125VAC primary.
The answer was "so you have a voltage problem?"......
(sigh), the answer was No I don't, everyone else does!
All we need is for the folks who so lovingly re-create
Dynaco Power Transformers to FIX these problems, not just throw them over the fence
just duplicate the original windings.
STOP, please STOP, wind the primaries for 125VAC, save
the planet, save the tubes, save the Music.
On a side note, the same issue
happens with the Mullard 5-20 Amplifier, the stock Mains
Transformer is way over dimensioned in the Mullard Book and a real
EL34 Slayer. You can read about this
saga of mine in my "Hand Made Amps" section and
how I learned about "Tube Amp Hypertension" the hard $$ way.
Refer to ST-35 "Stock" Voltage Chart
Below:
So... if the +385VDC is now reading +410-420VDC, the rest of
the ST-35 amplifier is also boosted?
ST-35 Published
Voltage Table
Hence even the Cathode
Resistor DC voltage read 17 Volts on my VOM, and this
my fellow Tube lovers is a Vintage Tube Amplifier
Hypertension diagnosis.
The Maximum Plate Voltage and Plate dissipation of an
EL84/6BQ5 tube is published in the RCA Tube Manual:
These are the nominal values, and some of the specs can
be exceeded, but never the Max Plate Dissipation, never, but if you like
Red Plates, be my guest
Pin #7
on the 6BQ5/EL-84 Plate connection and the voltages in this chart above, are referenced to Ground,
this makes a difference in the math when you calculate the Plate Dissipation,
you have to subtract the Cathode potential voltage from the Ground referenced
Plate Voltage, or you need to place the negative of your VOM on the EL-84
Cathode Pin and the Positive lead on the Plate Voltage Pin. This here is a
common mistake made by even seasoned Technicians, believe me, I made the same
mistakes. Its all part of being honest and willing to grow and accept/admit
mistakes.
Those who never admit to making a mistake,
live their lives within a mistake.
So we are
informed by Dynaco, in DC Voltage this chart, that the actual plate
voltage on the EL84/6BQ5 is by inspection:
+370 VDC - +13.5 VDC (Cathode Resistor Voltage Drop) = +356.5 VDC.
Does
+356.5 VDC = +300 VDC from the EL84 Max Plate Voltage spec sheet?
No.
Hummmm, we have
some of that funky vintage "spec game" tube stuff going on here.
The
ST-35 Cathode
Resistor is 95 Ohms, so we can now calculate from the ST-35 Voltage Chart the Cathode Current from the table.
Ik = 13.5 VDC / 95 Ohms = 142.1 milliamps (this
is 4 tubes as
the resistor is common to all)
So we divide 142.1 milliamps / 4 Tubes =
35.5 Milliamps per EL-84/6BQ5 Power Tube.
So when we calculate the quiescent Plate Dissipation on
the ST-35 Power Tubes:
P = V * I = 356.5 Volts DC * 0.0355 A =
12.65 Watts, another OUCH from the folks at Dynaco, at least they dared to
publish these measurements.
Now does 12.65 Watts = 12 Watts?
No.
Conclusion:
The stock Dynaco
ST-35 is a EL84/6BQ5 tube gobbler, and really requires
the 7189, so your amp will
likely eat up your EL-84's in a matter of weeks or a month.
From the RCA-30 Tube Manual the 7189 Tube specs are:
250Volts AC and 48 milliamps and this equals 12 Watts.
But we don't have 250 Volts in the ST-35 we have 356.5 Volts and 35.3 Milliamps
and exceed the Plate Dissipation by 0.65 Watts.
The
6BQ5/EL84 max values are at 300 Volts DC while the 7189 can handle up to 400
Volts DC on the plates, a different tube, way more robust than the EL-84/6BQ5.
This made amps, designed for 7189, literally go into Power Tube runaway current
when a lowly innocent EL84/6BQ5 was substituted by your friendly Tube
Substitution manual and even the Instruction Manuals!
Sending customers to the Tube Stores on a regular basis if their 7189 amps even
survived.
The EL-84 will sound glorious in a 7189 amp, then the EL84's will die or the
Output Transformer Primary will melt.
After 10 minutes the EL-84/6BQ5 Plates will glow red, the music will sound flat,
and maybe the amp will start to Hum if you are lucky.
The ST-35 amplifier was really designed to work
optimally with the
7189 Tube as it came from the factory, and can work with
EL84/6BQ5 with the Transformer Primary dialed-down to 115VAC with a Variac.
To park this amp is a "safe zone" you need to calculate
the properly corrected DC Plate Voltage.
So if we have 12 Watts Plate dissipation MAX, and we
like the music to sound correct, lets park the tubes at
35.5 milliamps.
Therefore the proper maximum Plate Voltage for the EL84
is 12 Watts = Vp * 0.035
so Vp = 12 Watts /0.0355 amps = 338 Volts DC.
Does 356.5 Volts DC = 338 Volts DC?
No
Granted, the EL-84 can always take a higher plate
voltage than the published specifications just as long
as we DO NOT exceed the Plate Power Dissipation of 12
Watts.
ST-35 Case Study Conclusion:
Dynaco execution had
Audio performance high on the feature
list, but the compromise was the parts vs. cost
conundrum.
Dynaco chose to use Diodes on the ST-35, and
this was a wimpy decision, including the fact that the
original Dynaco Plate and Filament Power Transformers
ran HOT back then, and today, you cannot hold your hand
on them for more than a few seconds after the pain
reaches your brain.
Dynaco kept costs low, they kept prices low, margins
high and the results today really require the use of a
high quality VARIAC to operate these ST-35 amps with
6BQ5/EL-84's in stock vintage
form.
On a separate subject if you compare the prices of these
kits nowadays in today's dollars, they were not a
bargain in any sense back then. But today most folks
haven't moved their price compass, and believe that a
$500 component, or a $1000 Tube are exorbitantly
expensive. These are actually bargain prices.
But you ask someone today to pay $1000 for a Tube Amp
and they would rather pay $1000 for an iPhone or a
Macbook Air, so fair enough.
But I do have one thing I must state about Dynaco, they wound
among the absolute finest Output
Transformers in the market, their frequency response is
still breathtaking today and the winding techniques difficult
to duplicate. These were at times wound by hand, by
people who blurred the boundaries of science, technique
and art.
My impression of the stock ST-35
Amplifier was always to be worried Power Supply Diode "Plate Voltage" slam, slowly hitting
the ST-35 Tubes with H.V. before they warmed up,
creating Plate Electron Stripping. This caused the tubes
to die a faster death.
This is probably akin to our "Sugar addicted" society
that consumes ridiculous amounts of Carbs, Sugars and Junk Food and complain
that they can't lose weight and exercise like mad.
I always thought that a nice 5AR4
Rectifier Tube with the slow turn on, would have been a better long term
solution, but the cost...... $$$, I chose the 5AR5 and
Hammons 272FX, the ST-35 sounds simply spectacular, relaxed, musical, even
bordering on mystical. And this is with the new Z-565 Output Transformers from
Dynakit Parts. These are amazing! I would order 20 pairs if I had the funds...
to make some ST-35's for sale...
The final piece.... Diode Tube Slam.
Yes Solid State rectification is great, but it is another bandit in the
Vintage Amp Hypertension issue another silent "Tube Killer".
So, I decided to pull out the Dynakit PA-774 Power
Transformer and sell it as I needed a 5V filament
section. The Hammond 272FX was the perfect choice,
although I am not sure it will fit a stock ST-35, I sold
my ST-35 years ago when I was cash strapped (darn).
What I did next, could go against common convention, but
I decided to replace the ST-35 Diodes in the Power Supply with
a Tube Rectifier and OMG, wow!
Yes a 5AR4 Tube Rectifier upgrade, slow turn on, wonderfully tight Bass.
A good basic secondary ST-35 Voltage is 300-0-300 VAC
with a primary of 125 VAC.
I also use a C354 Choke in
place of the 50 Ohm Resistor, why not?
The 272FX 125VAC tap is the worry free selection, and I use a
SPDT switch to go between 115 VAC and 125 VASC, and the safer one to choose and park the amp in
a comfortable place is the 125 VAC. The amp will work at
115 VAC but only when your Mains is 115-117VAC. At 120 VAC the 125 VAC primary
is the best choice.
I always like to park Cathode Resistor (self-bias) about
5% below the schematic or published DC voltages, it is
the safe zone.
The 272FX offers this unique 115/125V Primary that is just awesome
of Hammond to listen to the DIY Tube community and
respond with this option.
I have written many pages on the realities of
Un-Regulated Tube Power Supplies, so I will not go into
this here, you can find these rants throughout my
website.
Here is my Dynaco cover ST-35, and it sounds MARVELOUS.
The plate voltage is 15 volts below the published spec
and I am thrilled, the Hammond 272FX does not get HOT
like the PA774.
The bias board allows me to park the quiescent current
through the EL84's at different levels, and I will be
experimenting for the optimal place.
Here is
the result, and I am loving this with my Dynaco
PAS3x, that I also updated and is sounding fantastic.
UNREGULATED TUBE AMP DC - GOOD TO KNOW
STUFF
YOU MAY NOT HAVE ANY ISSUES WITH HIGH MAINS
BUT...... LIKE HIGH BLOOD PRESSURE, HAVE YOU TAKEN SOME READINGS LATELY?
2011 was a
year that has me in a life/career
transition. Having moved away from the
Caribbean in late 2010 after 15 years
the roots are still not in place. My
shop area is still in a transition and
projects have been delayed.
But I can
share thought's and ideas......
SUBJECT: VINTAGE AMPLIFIER AC VOLTAGE
CORRECTION or ADAPTATION
Voltage correcting transformers
are a must to effectively manage the
tube life and performance of Vintage Amps.
Not many
people understand how un-regulated power
supplies work. This is a key
understanding in owning Vintage Tube
amps.
It is a fact
that any odorous
and dusty old tube
amp will work best when connected to a 115 to 118 VAC mains. Power
Transformers of 40-50 years ago were
manufactured based on a 117 VAC primary
voltage, so the turns ratio was in fact
making the correct secondary voltages
when connected to 117 VAC.
If you want
to compare your voltage readings on that
old ST-70, ST-30, A500, A700, Fisher 400
or Marantz 7 you needs to have a Variac
and set the primary voltage to the one
that is published on the schematic.
The problem
we face today is that Primary AC
voltages in the range of 115 to 118 VAC are not
very common today. Unless
one happens to live very far from the
power station, in the Styx, you will
probably not measure 125 VAC with your VOM,
but 120V or 119V.
Now connect
that old Dynaco ST-70 to 125 VAC and you
will immediately exceed the DC voltage
rating of the first section of that
Un-Molested stock Metal Can Quad Electrolytic
FP capacitor, not to mention AC and DC
voltages sometimes 20 to 25 % above
nominal, I have seen 30% in some old
Stromberg Carlson amps I own.
In order to
appreciate what I am saying here, one must
understand that Power Companies always
prefers to err on the high side when
delivering commercial power.
Meaning
that less Power Loss = I2 x R, means less power lost
on the electrical lines, more profit,
less loss as heat when we buy juice from
them for our homes.
But ..... today's 125 VAC
mains does
not work well with most old tube amps, unless some method of voltage control
is used, or the design itself provides a 120 VAC tap.
Most vintage tube amp designers
happened to make their quiescent points
in the upper half of the input AC
voltage range, designing some headroom for
the rise in AC mains voltages.
But not
all did, and we shorten the life of our
tubes when we connect old equipment
directly to the power grid without
measuring with a DC VOM meter.
If you don't
believe me, you need to measure the
voltages and currents on your vintage tube amp
and compare them to the original values
shown on the schematic to
understand what "High Mains" AC does to
your precious tubes.
Also the AC Filament
voltages will often rise above the 10%
maximum allowed and dramatically shorten
tube life. When you operate a 6.3Volt
Filament at 7.5Volts, ouch!
Most current
production tube amps do not have this
problem, as their transformer primaries are
wound for 120 VAC and the voltages
settle down quite nicely.
But amps built from the
late 40's up
to the mid 70's have some issues as
their Power Transformers primaries were
using the 115 VAC standard, obsolete in
today's un-regulated power supply
designs but still commonly used.
Regulated
power supplies correct for this, but
99.99% of Vacuum Tube amps do not
implement regulation. Some Tube Preamps
do and in fact benefit from this. But
regulating 485 VDC is not an economical
thing to do, and would probably double
the list price of any Tube Power
amplifier. Also the complexity and size
of a regulated 500 VDC power supply is
$$.
High AC
Mains will make filaments wear out
sooner. You know when this is happening,
the tubes act like light bulbs and
actually provide illumination is a dark
room. When tube filaments are lighting
up your room, they are actually screaming for
help !
Remember
that 6.3V and 12.6 V (DC or AC RMS) are the nominal
voltages that the tube filaments
require.
The specifications will allow 10% over,
meaning 6.3 VAC + 0.63 = 6.93 VAC.
But..... operate your tubes at 6.93 VAC
and you shorten tube life.
This is a well known and scientifically
proven fact that has been common
knowledge since the late 50's. Wise
designers operate tube filaments at the
nominal value or 3% under.
There are
a class of tubes that will suffer dramatically from
high filament voltages, DHT Triodes.
These tubes have filaments that do not
work well with high filament voltages.
The filaments on these tubes will draw proportionally
more current as the voltage rises unlike
a resistor whose behavior is defined by
Ohms Law. In old radio's (I mean 1930's)
2A3 tubes actually had a rheostat in
series with the tube filaments that
allowed filament voltage adjustment over
a specified range to adjust gain.
ONE DIY SOLUTION TO CLASSIC TUBE
AMP HYPERTENSION
Build a "home brew"
- Balanced Power Toroid - in a box, with
a fuse and switch. Use a toroid that has
55-0-55 VAC on the secondary and the
common but outdated 115 VAC on the
primary. This solution will shave
off those extra volts and dramatically extend tube and amp life. Parts
Express sells some toroid 800 VA that
will work to power a tube amp.
Or you can
use a
60-0-60 VAC toroid and 125 VAC primary.
In any case the goal is to produce no
more than 120 VAC to your amplifier,
preferably 117 VAC.
In my modded
Transcendent Balanced Power unit I
replaced the 60-0-60 VAC Toroid with a
55-0-55 VAC keeping the same 115 VAC primary.
Un-loaded
and connected to 125 VAC, the voltage I
measure is 121 VAC-122 VAC.
As you load
the transformer with equipment, the
voltage will drop a few %.
The
more you load the transformer secondary,
the lower the settled voltage.
For
instance, if you have a Dynaco Stereo 70
that will draw about 1.5 amps when
powered up, this means about 180 VA of
AC Power.
You can use
a 500 VA Model so that it will load at
less than 50% of it's total capacity, I
would go with an 800 VA for extra
headroom in case you want to connect a
PAS3 Preamp as well.
The trick with
voltage correcting transformers is not
to load then past 50%.
1000 VA load
at 500 VA (4 amps AC RMS continuous)
800 VA load
at 400 VA (3 amps AC RMS continuous)
The 500 VA
model is far more practical as you can
also connect a Tube Preamp.
There are
625 VA, 800 VA and finally the 1000 VA
models to choose from.
The benefits of Balanced Power operation
are also realized here.
Any vintage
tube amp will run cooler with lower AC
Mains, the amp will sound better and you
will be happier knowing that your
vintage amp and precious tubes will last
longer.
The side
benefits of
Balanced Power are lower radiated
electrical fields from the AC Secondary
cabling and quieter performance.
The link
below will provide Toroid's for your
project:
http://avellindberg.com/pdf/avel_y23_range.pdf
Here is the
schematic of my "modded" Balanced Power
unit, You can build one in any metal box
that can be machined for the parts:
Order any
one of the Toroid's in the 500VA to
1000VA range, depending on your
application and build this into a small
project box.
You will need to machine a
mounting for a 120 VAC mono receptacle,
usually a Greenlee Hole Punch, or your
local machine shop can punch a correct
diameter hole.
If you want
to power a complete vintage tube
amp/preamp/etc. system with an 8 Amp
fuse, you need to order the 1000 VA Avel
Lindberg Model [Y236954].
Maybe you
can request that Transcendent Sound sell
you the Balanced Power kit without the
Toroid and you simply order the model
that I show on the schematic. I haven't
tried this yet, and my suggestions to
Transcendent Sound were not well
received. The suggestion was to use a
bucking transformer on the primary. I
don't see this as a solution but a fix
to a problem with their design.
When I built
the Balanced Power unit from
Transcendent Sound I connected my amps
to the unit (I had not even bothered to
measure the secondary AC RMS voltage)
and noticed that my amps were GLOWING
BRIGHT and the plates of the 6550
tubes were cherry red.
I measured
the loaded secondary voltage on the
stock design and my meter read 131 VAC....
yikes!!!
My plans in
2012 are to build a few "Vintage Tube Amp Savers"
in stock for sale with the option to
have an Analog or Digital meter on the
front panel.
Here is the Balanced
Power Unit, built inside of a discarded and gutted MASTR III GE Repeater
Power Supply.
The courtesy AC Duplex was just perfect and so were the fuse
holders.
Here is the inside of the unit. Avel-Lindberg 800 VA Toroid 115VAC Primary,
55-0-55 VAC Secondary, just perfect for Vintage Amps.
AC Output is around 121 VAC No Load and 115 VAC Full Load, but typically
operates at 117 VAC for most of the time when the AC Mains
is around 123 VAC. No bucking transformers, just great innovation here and
recycling old equipment.
<<<Next on ShermanAudio>>>
Return to Home Page