Hum in system when only amp is on

It is not a problem if the system does not hum in normal operation. Since you would never operate the system with just the amp on and not the preamp the question is moot. Most amps will hum loudly if you pull the IC out of the preamp and touch the signal pin with your finger. Is this a problem? NO, because this is not how the system is normally operated.

Follow Joe Abram's advice and you will never have any hum so you will never have a problem. Sit back and relax, enjoy your hum free system :>)

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.

I do normally turn the pre on first. However when a dvd is inserted there is a hum until the bit stream is sent to the pre. (this system does dual purpose HT/2channel)

I did try removing the ground, and the hum went away. But I see that is not advised by Theta. I will use automation to mute the pre to solve the hum problem.

Also I will switch the direction of the IC's.

Thanks for all your help. You all are very helpful. I thought I knew how to set up this system, but now I see there is so much more to know when dealing with seperates.
As always enjoy the music...

Ian

Ian, in my heart of hearts, I feel the warning from Theta is mainly a liability issue, and that you shouldn't be paranoid about ruining the amp if you float the ground . . . . . but if you are, then ground the amp, but not anything else (oh, and then point the arrows of the preamp-to-amp ICs toward the amp as I mentioned earlier.)

Neil

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Try removing the grounds on the other components and see if the Theta still hums. I know the Theta does have a little different grounding scheme than some amps.