|
The buzz is coming from 120 Hz currents through the field coil of the speaker. That is used as a filter choke. The rectifier starts working within a second or two but the other tubes don't function for about 15 more seconds, so it has to be the power line through the speaker. Pull the output tube and it will still hum.
Increasing output filter capacitance probably won't fix it, since if anything it will increase the hum current in the field coil. Increasing input capacitance will help, as long as you don't go too far and exceed the peak current rating of the rectifier tube.
|