Tube Amp Archive

Great responses so far! I had completely neglected to take into account the different cathode resistances. One of my next questions was going to be about the operating point of the 12ax. These values look to put the tube at a very low area of a plate characteristics graph. At one point I had reworke...

I'm working with a small 2 tube amplifier (12ax7, 7868). The supply voltage to the preamp is the correct value (280 V) from the schematic. The voltage on the first 12ax plate matches as well. However the second plate voltage is over double (260 V) what is written on the schematic. I have tried two t...