• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Know this tube? 10J12C or 10X12C ...

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Dear fellow DIY audio tube-freaks:eek:

I feel lucky: I have the possibility to buy several pentode driver-tubes that the vendor says is equivalent to the WE 310A - for a reasonable price compared to the WE 310A, STC 4310A or Svetlana 310A ...

In a book by Jean Hiraga it is quoted that the Russian 10X12C is equivalent to WE 310A ...

The puzzle:
The vendor insists that the tube is a 10J12C ...
The "J" in Kiryllic resembles an "X" in the latin alphabet.
It is printet 10 and Kiryllic "J" (latin "X") and 12C on the tubes ...
It may be read 10X12C - if one doesnt know the Kiryllic letter.
The vendor have datasheets in Kiryllic - and states this tube as being "analogue" to the WE 310A. He isn't very skilled in tube-gear - but has told me that the data for the heater voltage and current are the same as the WE 310A (10V/0,34A).

I can not find any data for the 10J12C anywhere ... Is this a tube that even exists?
Is this actually a 10X12C - only that "we westeners" have mis-read the Kiryllic letter?

Can anyone help?

Regards, Aril
This letter that looks kind of like an X with an added vertical line through the mniddle (kind of like >+< ) is often and WRONGLY transliterated as J. In fact, it should be Zh, transliterating it as Z would be less of an error as Z is not used in Russian tube coding.

The tube you have is a 10Zh12S if we transliterate correctly, and I am attaching the datasheet:


  • 10z12s.pdf
    67.8 KB · Views: 277
Yes, it is quite confusing. Even some Russian sites transliterate the letters wrong which makes it difficult to figure out what the tube is until you see the actual cyrillic lettering. I've spent months hunting for datasheets and correcting these mistakes...
It is pronounced Jh, or Zh, looks like >I<
10Jh12S was used in telephone multichannel systems before 1960'th
Later it was replaced there by a loctal 12Jh3L - I am not sure it was the same internally. In later stations 6Jh1P were used, but I think they are not the same...

An externally hosted image should be here but it was not working when we last tested it.

Here is the photo (the left one is 10P12S, a power pentode).


I believe 10Zh12S is close to later 6Zh32P tubes that were used mostly in microphone and tape head preamps.


When I was a kid I made an amp using 10Zh12S and 10P12S tubes.
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