Hi @Trerik, this is @Cyphers orginal post – he was talking about reducing the plate voltage to help prevent tubes from blowing fuses. Some new tubes are on their way to him (or will be… Gil needs to respond to him about that 
).
The hum issue and the blowing tubes issue are seperate.
Hum is normally caused by energy from the power supply leaking into the audio signal; this is unrelated to bias. For example, heater filaments can couple/leak energy into the cathode, and it then becomes audible.
@Trerik thanks for waiting I will get back to you in a day or two about your noise issue.