Metropoulos Forum

Larry or anyone, can you tell me what means those numbers on 12ax7s ex. a GE 7025? What are the caracteristics/differences between those numbers...???

Thanks!!

cv4004 is a mullard military grade...

Once upon a time some decades ago, there definitely was a difference between the 12AX7/ECC83 and the 7025 - not a difference in their electrically parameters, but a difference in the construction.

The 12AX7 was made for usual use, while the 7025 (that's a US industrial number) was more rugged in its construction, to withstand a higher amount of vibrations, which might occur when used in some machines, medical equipment, cars, planes, aso.

Therefore the 7025 always was lower in microphonics compared to the usual 12AX7 - and therefore this tube was recommended as the input tube in guitar amps.

But meanwhile there's no difference anymore with the current produced preamp tubes, no matter how they are labelled.

Larry

novosibir wrote:Once upon a time some decades ago, there definitely was a difference between the 12AX7/ECC83 and the 7025 - not a difference in their electrically parameters, but a difference in the construction.

The 12AX7 was made for usual use, while the 7025 (that's a US industrial number) was more rugged in its construction, to withstand a higher amount of vibrations, which might occur when used in some machines, medical equipment, cars, planes, aso.

Therefore the 7025 always was lower in microphonics compared to the usual 12AX7 - and therefore this tube was recommended as the input tube in guitar amps.

But meanwhile there's no difference anymore with the current produced preamp tubes, no matter how they are labelled.

Larry

Larry you are a great addition to our community here, you rock coach, thanks for the crash course on NOS 12ax7s....

George we should add a NOS tubes topic, there is so to learn, this would be a great addition to the board.........

I read somewhere that the "CV" prefix stands for "cryo-valve", which means it's been cryogenically frozen to improve the molecular stability of its elements.

Larry, I can't find the thread on 161s and 163s

Which one is more rock and roll again, the 163 right?

5150loveeddie wrote:Which one is more rock and roll again, the 163 right?

Right! But I63 (a capital "i")

Larry

novosibir wrote:

5150loveeddie wrote:Which one is more rock and roll again, the 163 right?

Right! But I63 (a capital "i")

Larry

Oh yeah really it an "I" there not a one ??