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Tube inventory time

Sam Cogley

Sam Cogley

Last of the Time Lords
Subscriber
I decided to go through my 12A_7 tubes now that I have a better idea what I'm doing - my box of pulls was a disorganized mess.

The results...

grey plate RCA 12AX7, Lowrey branded: 19
black plate RCA 12AX7, Lowrey branded: 5
Raytheon 12AX7, Lowrey branded: 1
Sylvania 12AX7A: 5
Mullard 12AX7A, IEC branded: 1
unknown 5751: 1 (tube appears to carry EIA code 142, which makes no sense to me. It's branded for a Heintz and Kaufman Gammatron, marked Made in USA. Plate structure and color strongly resembles the black-plate RCAs.)
black plate RCA 12AU7: 35
Raytheon 12AU7, Lowrey branded: 2
clear-top RCA 12AU7A: 1
Sylvania 12AU7A: 8

Now I need a working tester...

Any thoughts on which tubes will have the best sound, operational condition aside?

Edit - a bit of research has revealed that the H-K 5751 was most likely manufactured by GE.
 
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I recently did some 12ax7 tube rolling, make sure each tube is burned in and played until fully heated before judging it's sound character, some tubes sound just terrible when they're cold.

I'm still stuck on my gold pin JJ ECC803S tubes, I keep going back to those. :thmbsp:
 
I found one lonely ribbed-plate Telefunken 12AX7 that I forgot about after I posted last night. I think that's it for the 12A_7 supply. No 12AT7s that I found, which is a bit frustrating - I have a couple of tubeless items that spec 12AT7s in certain spots. From what I can tell from the manuals, the 12AT7 is similar to the 12AX7, but with somewhat lower gain.
 
Is that 5751 a two mica or a three mica. The micas are the horiontal pieces at the top and bottom of the plates.
 
Now that the Triplett is working, I really should start testing these. A random sample all tested strong.
 
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