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12AX7WA

Sensibly equivalent to:
7025 ECC83
    
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The 12AX7WA is a low hum audio amplifier double triode and an improved version of the 7025 The WA suffix denotes a special quality type.
This valve was designed for high gain small signal amplification. The 6.3 Volt heater rating is with the voltage applied between 4 + 5 and pin 9. When used with the connections made to pins 4 and 5 the rating is 12.6 at 0.15 Amp. The electrical characteristics and pin connections almost match the ECC83.
The Lettering gives the Type as 7025/12AX7WA, the maker's name and the fact that it was made in Russia. The lack of Cyrillic characters suggests that this was made for export.
The anodes have a greater front to back dimension than the original 12AX7. note also the presence of an electrostatic screen that was never present in classic audio double triodes but only seen in RF devices.
The thin glass tube envelope is 22 mm in diameter, and excluding the B9A base pins is 48 mm tall.
Reference: Datasheet.

 

Pin Connections
B9A
1
2
3
4
5
6
7
8
9
a(2)
g1(2)
k(2)
h
h
a(1)
g1(1)
k(1)
hct

 

Absolute Maximum Operating Conditions
Pentode
Vh
Ah
Va
Vg
mAa
ra
gm
μ
6.3
0.3
250
-2
1/2
62,500
1.6
100
Thanks to Frank Philipse for supplying the above PDF datasheet.
Updated November 14, 2018.
shape:thin.glass.tube construction:all.glass type:double.triode age:1950.1960 base:b9a heater:6.3v pins:9 pin:1.a(2) pin:2.g1(2) pin:3.k(2) pin:4.h pin:5.h pin:6.a(1) pin:7.g1(1) pin:8.k(1) pin:9.hct
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