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12AX7 is a miniature high-mu (AKA high gain and high transconductance) twin triode. Each triode section has separate cathode

connections. 12AX7 was originally introduced in 1947 by RCA and was originally intended for voltage amplifier, phase inverter and multi-

vibrator or oscillator application. After almost 60 years, 12AX7 still sees wide use in guitar amplifiers, audio amplifiers and ever growing

list of recording equipments.

Current Production:

12AX7 equivalent tubes are being produced at Reflektor, Ei, JJ and Chinese factories today. Current production 12AX7 on market today

are:

Sovtek 12AX7LPS

Sovtek 12AX7WA

Sovtek 12AX7WB

Sovtek 12AX7WC

TungSol 12AX7 Russian-Issue

Electro-Harmonix 12AX7EH

Electro-Harmonix 12AX7EH Gold

Shuguang 12Ax7C9

EI 12AX7 Silver Bullet

EI 12AX7 Elite Gold

Plug compatible variations

12AX7A/7025 - Lower filament hum

ECC83 - European Version

B339 - Marconi/GEC version

6EU7 - 6.3V filament version originally by GE

12AD7 - Fatter filament with lower hum

20EZ7 - Series filament 100mA

5751 - Aircraft/military and computer application

5751WA, 12AX7WA - Vibration resistant version of applicable types

6681, 7058, 7729 - Higher reliability mobile applications

6851 - Bendix aero space version of 5751

6057 - Brimar high reliability

E83CC - Philips/Siemens Special Quality version

ECC803S - Frame grid lower microphonic version

M8137 - Long plate version by Mullard

CV492, CV4004(M8137), CV4017(5751), CV8156, CV8222, CV8312, CV10319 - Various British CV versions

Other variations of 12AX7:

6AV6 - Has one unit of 12AX7 with diodes

6DR4 - Half of 12AX7

6BK11, 6K11, 6Q11 - Compactron versions

6C10 - 3 x halves of 12AX7

5755/WE420A - Very low frequency/DC amplification version by WE and others. Super low microphony.

ECC83M - 6.3V only version with shield like 6DJ8

6CC41 - Variation by Tesla

6N2P - Russian copy

12AK7 - 12.6V only version by TungSol

ECC808 - Valvo super quiet version with filament and grid shields. Often found in vintage Telefunken equipment

E283CC - With shields like ECC808, frame grid like ECC803S The ultimate low noise 12AX7

Source: BOI Audio Works

Material herein presented for educational purposes per Fair Use.

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Last updated 27 Sep 2013

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