Hum in system when only amp is on

I am getting a hum when the amp is turned on but not the preamp. The hum goes away when the preamp comes on. Does any one have any ideas?
My system:
Theta dreadnaught 5 channels
Cary cinema 6 preamp
audioquest jaguar unbalanced rcas
dedicated outlets

This is not an answer to your question, it's just a rule we ALL gotta follow:
ALWAYS turn your preamp on (and give it a moment to stabilize) before turning on your amp. ALWAYS turn your amp off before your preamp.
Best of luck,
The arrows on the ICs connecting the preamp to the amp should point to the preamp. The preamp AC cord should be grounded, but the amp should not (it's grounded through the ICs and the preamp) and you should use a "cheater" plug on the amp's AC cord plug so that you are only plugging two prongs into the wall, not three.

Try those two things, and see if the hum doesn't go away.
Nsgarch, I don't think the directionality of the IC's would make a difference in Ian's problem, but my understanding is the arrows should go in the direction of the music -- thus, pre-amp to amp.
I agree that floating the ground on the amps, but not the pre-amp, can solve a ground loop problem. That's what I do, but I've been told it's not the safest solution, either.
Ncarv, you might want to read the description of their x-Stream power cords on the PS Audio site. They even provide their cords with a removable ground pin for that very purpose.

As for the arrow direction, Ian is using Audioquest single ended Jaguar ICs. These follow the standard Bruce Brisson "shotgun" design a la Monster, MIT, Straightwire, etc. Meaning that the shield is connected to the ground ring at the arrowhead end of the cable and not at the other end ("floated"). You want to drain the shield to the preamp, since in a star-grounding arrangement, that's the one grounded component. It really has nothing to do with signal flow since a cable will acclimate to either direction of signal flow during break-in. This unfortunate misunderstanding arose as a result of cable manufacturers wanting to give the consumer an oversimplified explanation for orienting their cables. And in fact it works when you're talking about source-to-preamp connections, but does not apply in preamp-to-amp connections -- UNLESS your amp is the only grounded component. However that won't give you star-grounding, which is the recognized best method for getting the most noise reduction.

Hope that explains it :~))
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, 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.)


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.