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I am new to 12au7's and am trying to ascertain quality, provenance and vintage of the tube in photo. They came in my preowned VTL Mkiii preamp and sound good to me, but though experienced with 6sn7's, I know little about these.
Thank you.
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It is hard to identify the factory code from the photo, but its probably a Mullard Blackburn long plate. However, the date code is visible, indicating date of manufacture as December, 1956. The square getter in the tube is consistent with this year. The factory code will definitely identify factory origin of the tube.
unfortunately, I've had my share of noisy or microphonic NOS Mullard ECC82's. I don't used them anymore.
It is a Mullard long plate 12AU7 also called an ecc82. I think that it is from the early 1960s , if you look in oblique light you should see the manufacturers code, which will date it precisely. So yes it is a well regarded tube (high quality) the provenance is impossible to trace at this point. I does not have the features of a tube made for the military, but that can't be ruled out with certainty.
Steve
Yes, that is good tube for the type.
What do you want to know? Are 12AU7 the best tube type ever produced for audio? No.
I don't have much choice, as that is what the pre uses. Anything better in the 12au7 family than the pictured tube, that you recommend?
I will have to check again to see if there is an etched date.
Thx.
Neal
"Anything better in the 12au7 family than the pictured tube, that you recommend?"
IF extra heater power is available, you can try 12BH7s, where 12AU7s go. The 12AU7 draws 300 mA. of heater current at "6" V., while the 12BH7 draws 600 mA. at "6" V.
RCA 5963s are an "affordable", decent, 12AU7 equivalent that may be worth trying. TFK and Mullard NOS is pretty darned expensive.
Eli D.
Here is a better photo:
Neal
Does it have an etched date code?
That always tells the tale.
Please report back with what the 2 etched lines read on the tube. The format should be something like k6-number (1st line) B-number-letter (2nd line).
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