12AU7 and 12AX7 long black plates vs short black plates. Any difference ?

Best of the best 12au7's CBs Hytrons of the 1950's or the square getter rca JHY12au7, I will lookup the other super 12au7 tube in my stash later this evening. You need to locate yourself and buy a  NYAL George Kaye Small Signal Tube Tester if you are serious.

Best of the best 12au7's CBs Hytrons of the 1950's or the square getter rca JHY12au7, I will lookup the other super 12au7 tube in my stash later this evening. You need to locate yourself and buy a  NYAL George Kaye Small Signal Tube Tester if you are serious.

https://www.audiotubes.com/audtube.htm

Jessie Brent Tubes closing March 5, 2026.

Better look and stock up quick ...  BUT great information on audio tubes, well worth the time to browse. One cannot help learning a great deal about our beloved vacuum tubes and the variants!

https://www.audiotubes.com/12au7.htm

https://archive.org/details/InsideTheVacuumTube

Have fun!!

I read what Brent Jessee has to say as well. You'd be hard-pressed to find anyone who knows more about tubes.

5814 (A) tubes draw more heater current than 12AU7. I guess, it is not always a good idea to use them as a substitute. Better ask the manufacturer of your equipment.