PATB
1000+ Head-Fier
I am not 100%, but the always ON bias must be getting the 580V bias voltage from the same power supply. In that case, if you have transformer hum, you are going to need more mechanical damping or clean up the power to your amp.
Do you use an AC conditioner? Try plugging directly to the wall or another outlet in the house.
Do you use an AC conditioner? Try plugging directly to the wall or another outlet in the house.