Tubes Asylum

RE: I got SOME music by lowering the - bias

141.239.172.61

This Post Has Been Edited by the Author

In Reply to: RE: I get no music out of mynewly built amp posted by DAK on October 17, 2016 at 19:12:52

I played with the bias circuit, removing the 5k ground resistor. This allowed the bias voltage to be less negative and thus raising the cathode current. In one channel the bias current i was able to adjust to 80ma which moved the tube out of cutoff and allowed the music through. So, i know that the bias system just needs to be tweaked to work ok.
The next part is the 6j5 driver tube. The music that is coming from the amp is very weak which i believe is the driver stage underperforming. While playing with the bias i also checked the voltages on the 6j5 and these are the values. Anode voltage is only 45vdc, roughly for both channels. Cathode voltage is about 1.7vdc from a 380 ohm resistor. The plate resistor is 105k while the B+ supply is about 275vdc. This resistance must be too large so i am going to change it. Any suggestions? I am thinking 33k which is pretty standard for 6sn7.
The complicating factor is the plate to plate resistor in this circuit which is 100k. I guess, i will install the 33k and see how it affects the driver circuit.

Follow Ups: