Thanks. I've downloaded it; I'll see if I can make sense of it.Hi, i would suggest that you consult the RCA tube databook, RC30 and look at the tables on RC couples mplifiying stages, those tables contain values of plate load resistors , grid resistors and cathode bias resistors for a give B+ and voltage gain...
You may be right, and it has more gain than I need, but I don't have the experience (knowledge) to change things by myself.I have never got on very well with 12ax7's.
Always ended up using a different model like the 12au7.
It seemed to be more stable and less noisy.
I have used 2 12ax7's halves in series and the tube just fed back on itself.
When I look around there seems to be plenty of amps with the halves in parallel, maybe they found the same problem ?
Having said that 2 12ax7 halves in series is around 10,000 gain so not surprising it was unstable !
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