Tube Amp Archive

Kind of like what is shown in the attached. The "Heater Reference" connection goes to the center lug of your hum balance pot. The 220K:22K voltage divider should be moved down the PS string to the "D" location shown in the schematic early on in this thread. Yes! Do make sure that none of the hum ba...

Bias up the center lug of the hum balance pot with about 50 volts of B+. Pull if off the last preamp tube power supply node and thru a dropping resistor and another filter cap (16 uf at 400 is fine) to un couple it from the preamp. One other thing to check since you have this hum with just the outp...

What things have you done so far to try and cure your hum issue? First let me describe the hum: 60Hz with Volume of both channels all the way down, turning up the volume does not increase the hum, its just always there. Well so far I have changed all the tubes including the rectifier, this had no e...

I too am trying to tame B25 hum, was curious if you ever solved your problem.