Theta, in the Dreadnaught's owners manual, specifically says DO NOT USE THE AMP WITHOUT A GROUND. Why that is I don't know but they are emphatic about not using cheeter plugs with it. Check your owners manual or call Theta.
Now, is the hum coming from the speakers or the amp itself. I have heard a few Dreadnaught power transformers hum pretty loud at times. It is a very large single 2.2KVA (2200 watts.)
If the hum is not there when the whole system is up, I wouldn't worry about it. Do as the guy above says, turn on the preamp and let it set in, then the amp. You can always leave the amp in stand-by so it stays ready. It will not output through the speakers in stand-by but the circuits for the most part are hot.
Now, is the hum coming from the speakers or the amp itself. I have heard a few Dreadnaught power transformers hum pretty loud at times. It is a very large single 2.2KVA (2200 watts.)
If the hum is not there when the whole system is up, I wouldn't worry about it. Do as the guy above says, turn on the preamp and let it set in, then the amp. You can always leave the amp in stand-by so it stays ready. It will not output through the speakers in stand-by but the circuits for the most part are hot.