I have a '79 JMP MV with EL34's and I just did the mod of putting 1 ohm resistors from pin 1 to ground on each output tube. Cathode follower method I think. I know its not the most exact method for bias but I think its the easiest. I have about 390 VDC on the plates so about 36ma's for 70 percent. With this method you get the screens I think too in the measurement so 36 would be a little conservative(lower than 70 percent) Anybody Have this kind of amp and can tell me where a good ma reading would be? With the screens in the measurement, the voltage drop across the resistor to ground, the percentage will be lower than 70 @ 36ma's. I heard that these kind of amps like to be biased a little hotter to sound good. Does anybody know how I can subtract the screens from the measurement and get a more precise measurement? Its probably just a few ma's but it would be nice to know.