Common Vacuum Tubes for Music Enjoyment

Military Tube Handbook 1963





Thank you Mr. Lee DeForest

Thank you Mr. John Flemming

Vacuum Tube Pioneers.

They lit the Lamp and made possible the Amp

My NOS "Stash" in the Garage

An assortment of TV and Audio Tubes

I gave most of them away years ago but still kept the good Tubes

My Tube Testers

If you want to avoid frustrations, buy a basic Tube Tester

Below my operational Tube Testers, each one does something well

as there is no "Single" Tester that does it all, that is still a myth

Even the great AMPLITREX has some quirks on 4 pin DHT's

But its minimal, considering the power of the AMPLITREX Software

The AMPLITREX is an amazing tool for people who sell tubes

I want one.... some day.... will buy if I open a Tube Business

EICO667 - Pass/Fail Tester

A reliable tester for Portable, General Purpose use

I carry this on every Tube Road Trip, especially for Hammond Organs

Power ON, do the Settings, Install Tube, wait 5 minutes, Test

The EICO 667 does not test 4 Pin 2A3 or Rectifiers :(

There is an EICO 725 Adapter that creates an EBay bidding panic

when they come up for sale.....


Some Power Tubes do not measure correctly on the Eico 667

meaning if you have a set of new Power Tubes

especially 6.3V @ 1.5 Amp Filament

on the EICO 667 they may measure ?, or slightly into REPLACE

Make sure you compare against a known good tube

don't immediately assume the tubes are bad

Lots of Vintage Tube testers exhibit some of this

Just don't throw tubes away based on one tester result

(Also capable of Dual Triode relative balance testing)

MAXI PREAMP II - Noise and Triode Balance

At the price, you just cannot find a digital tester for Preamp Tubes

I always first test for Noise, then Triode Balance

If a small signal tube is noisy, I set it aside for other applications

OTTO-1 - Matching @ 250VDC

Good for matching up to four (4) small Audio Power Tubes

Nothing else really..... Russian made

I replaced 4 burned resistors and a bridge rectifier

I got this for $75 broken

Caveat: At 250 VDC, it does not prove that Tubes are matched

It gives you a relative notion, as most Power Tubes use more than 350V on the plates

Actually matching Power Tubes requires measurement at several plate voltages

to derive a matching curve


Tester Donated to - Antique Wireless Museum, New York

May future generations enjoy this classic tester where it belongs, in a Museum.

This one had a full set of Western Electric Cards, plus a new set of regular Tube cards.

Long live Hickok Testers, the clunk of the solenoid is priceless....

Duncans Amps

A must have bookmark

My reference for more than 20+ years and counting 21, 22, 23....

You cannot find a better Tube Reference Website

Since 5/8/96

Audio Power Tubes - limbic system activator

KT-88/6550 - Cavernous lows & very polite highs, trash metal crunchers, surprisingly good with Horns and Lowthers

KT-66/6L6/5881* - Layered, tonal, great for both HiFi & Guitar Amps, many nice variants, a chameleon of Tones

SPECIAL HONORABLE MENTION: 7355 TUBE (RIP) - Small 6L6 variant, brilliant design, out of production, the 7591XYZ was a great 7355 sub, until SOVTEK production ceased

KT-77/EL34/6CA7 - Midrange Guitar "screamer", with a nice leading edge, crystal clear HiFi, very nuanced, KT77 smoothest

EL-84/6BQ5 - Musically engaging, great for Classical Music, a smooth operator, vocals are crisp and clean

7591/7591A/7868/6GM5 - Sweet sound, deceivingly smooth at high power, can kill speakers, current production is Russian

7027A (RIP) - Nice Warm & Detailed Sound, used when Tubes roamed the market

8417(RIP) - Audio Power Pentode, late bloomer, akin to a V8 and Oil Price Hikes, long out of production

6F6 Metal / 6F6G Glass (Russian 6F6S Glass) - Think old Tube Car Radios, fabulous tonality, best kept DIY secret, listen here on 16 Ohm PSV-2

6V6/7408 - Lighter version of 6F6 but different sound, filaments are not as hungry as 6F6, can be bright, glassy-clear

6AQ5 (RIP) - Out of production, have a few on hand, will made a prototype amp, with plans to enjoy later

6CM6 - (RIP) also out of production, fantastic Jazz and Vocal, listen... a small 6V6, similar sound character, glassy-clear

E80L/6227 (RIP) - European 9 Pin Pentode. 10,000 hour PQ version, on my short list of Tubes to use, uncommon

2A3 - Single Ended Holography, Fine Bourbon & Single Malt Scotch, look for the Single Plate Sovtek today. NOS usually worn/used

300B - The trusted voice of DHT Class A - the golden S.E. standard - Expen$ive but Musical, used in Preamps as well

Special Mention RF Power Tube;

6146B - Commonly used for Radio Transmitters, seen in Audio Amplifiers, bully of the block. Easily capable of 75W in PP

Small to Medium Signal Tubes

Line Stages, Tone Controls, Phase Splitters & Buffers

ECC83/12AX7 - High-Mu, Dual Triode everyone knows something about, it is very common in Audio

ECC81/12AT7 - Medium-Mu Dual Triode, common in Guitar amps, seen less in HiFi amps (Fisher SA300)

ECC82/12AU7 - The true 9 Pin chameleon, Low-Mu, versatile, ubiquitous, handy, the toolbox of small signal tubes

12DW7/7247 - Half of a 12AX7 plus Half of a 12AU7 cool tube, (Dynaco ST35, EICO 2036)

ECC88/6DJ8/6922 - Frame Grid design, a Love/Hate HiFi reputation, I love'em Hot and Bothered (Audible Illusions)

ECC85 - Used sparingly in Audio, very sweet, much more common in German Amps (Grundig)

EF86/6267 - A small Pentode Tube, everyone needs to listen to, most never have (Mullard 5-20)

6C4 - This is half of a 12AU7, small and petite, very cute, used in Acrosound Preamp & Hammond AO-28 (RIP)

6SN7/5962 - The Bulldog of Small Signal Gain Stages, robust and musical (Cary Audio SLP-5)

6J5 - This just half of a 6SN7 (think 6C4/12AU7), killer tone, a best kept secret, out of production (RIP)

6N7 - Rare metal audio tube, Stromberg Carlson Theater Amps (Stromberg Carlson APH50)

6SL7/5961 - Less seen in amps, Cary Audio used them in the 90's (CAD SE300)

12BH7 - Robust dual triode, awesome & beefy, great driver tube (Hammond AO-28)

ECC99 - The new kid on the block, speaks with an accent, nouveau 12BH7 (JJ Electronik)

6C45P - Best kept secret for Phono Stages, used in DIY for those in-the-know (Transcendent Sound)

6N1P - More robust than a ECC88/6DJ8, great driver for DHT Triode Tubes (ShermanAudio Kismet)

7199 - Out of production tube (RIP), Pentode/Triode, Russian version hit-miss (Dynaco ST70)

6AN8 - Out of production tube (RIP), Pentode/Triode (Dynaco MK3, some Japanese Amps)

Tube Rectifiers, unsung heroes from the engine room

"An unfair reputation" when it comes to Music, Tube Rectifiers absolutely rule the tone department

Tube Rectifiers are gentle on their fellow Tubes, fairly slow turn-on, no voltage slam

GZ34/5AR4 - 5V/2A Superman of tube rectifiers, general purpose (Dynaco ST70)

GZ37 - A somewhat filament hungry 5V/2.8A variant of the GZ34, British, rare & expensive

Type 80 Globe - Paleo Rare Tube Rectifier, too much for me as well, for museums

5Z3 - Also rare, museum stuff, not for DIY, unless there is extreme nostagia

5Y3/5Y3GT - Neutral 5V/2A, very reliable when operated within their maximum ratings, quick-on

6X4 - Lighter 6V/.6A version rectifier, mostly used in Preamps (Scott LC21)

6C4 - Small sized rectifier common in the 60's, Silvertone Guitar Amp, also Hammond Preamps

6CA4/EZ81 - Common small 6 volt rectifier, used in vintage preamps and Euro Tube equipment

5V4 - Rare now, 5V/2A sweetie, nice for medium powered amps 20 to 30w

12X4 - A 12V/0.6A version of a 6X4, same tube, different filament (Dynaco PAS)

6CA4/EZ81 - Like a 6X4, but not as popular, 1amp, think VOX (Leslie Reverb Cabinets)

5U4/5U4G - Robust Rectifier 5V/3A, tall, dark and handsome (US Navy)

5R4GY - That Sexy glass bottle, 5V/3A often seen with Brown Shorts (JAN)

5R4WGB - Potato Masher Rectifier, totally ready for Dinner and Battle (Military Grade)

6AX5/6X5GT - Popular 50's-60's 5V rectifier, similar to 5Y3 in ratings, 5V/0.6A from the 50's

274B - Western Electric, high end tube, available today, must be nice, Expensive as F, $$$

Tube Datasheets

I will now walk through a Tube Datasheet to explain how to pick out the essential electrical

characteristics of the Tube, and correlate these to the DC operating point to check if the Tube is operating

in the Safe Zone. It is with this information how you can do a check for "Power Tube Hypertension".

I will also look at a 12AX7 tube as well so it becomes clear that both Power and Small Signal tubes share

a common electrical situation, despite their different 'roles' in the amplification, gain stages and

output stages.



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