12a?7

jsb

Member
Messages
73
Is there a way to tell what a 12a?7 is if there is no label on the tube? I have a couple that have no stamp on them and was wondering if, by sight, there was a way to know (12ax, 12ay, 12at, etc.)

Thanks for any help
 

Torren61

Member
Messages
2,035
Get a magnifying glass and hold the tube up to the light. Rotate the tube until you can make out the markings. You'll see something. Have a Sharpie handy and write what you see on the tubes.
 

Timbre Wolf

Hyperspatial Gravity Surfer
Platinum Supporting Member
Messages
9,998
12AX7 and 12AU7 often look identical to each other, on the inside (if from the same factory, same era). Tell them apart by plugging them in and comparing the audio output level.

12AT7 are visually distinct from 12AX7 and 12AU7.

You can post photos of your mystery valves and I can try to help.

- Thom
 

sickboy79

Member
Messages
13,070
Agree with Thom above. I'm not the tube expert that he is but, yes a 12AU7 looks SUPER similar to a 12AX7. The AT version is visibly different for sure.
 




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