Can I ground my preamp?

Wow, this is more complicated than I thought. I think I will try your suggestion first, Stingreen, to see. BTW, the amps are the only grounded components (CD, DVD, and preamp are all non-grounded). Am on work travel, but I'll report back when I get a chance.

If you are having a ground loop problem you can drop the ground on your amps and leave the rest alone. You don't have to ground any components.

Tvad,
I do have have Ground Zero and used it in various system configurations. It definitely works, but requires quite a bit of fiddling, and in some cases is not 100% effective.
I have to admit though, I probably didn't have enough patience to follow the protocol to the last letter.

I have a Granite Audio grounding system. You can hear some reduction of noise with some settings, but it does not resolve a ground loop problem.

I have yet to find a system that was not improved making the preamp the only grounded unit. Some are very concerned about the possibility that and amp can have the hot wire somehow come in contact with the chassis and a person who is grounded come in contact with that chassis. There is certainly some probability of that happening but it is very remote. Canada doe not allow cheater plugs to be sold, which is over the top in my opinion. Synergistic Research sells the best cheaters that I have ever heard.