Can I ground my preamp?

The preamp, being the heart of the system, should be grounded. The amps, for safety reasons, should be too, but for audio reasons (ground loop prevention) they should not. If the amps hum when grounded through the AC cords, it indicates that the manufacturer has not done their grounding homework (it is possible to have the amps grounded and **not** hum at the same time)- so the best method probably is to float the grounds of the AC cords with cheaters.

At any rate the preamp *should* be grounded, although I suspect it already is since you are getting the hum.

I had a hum problem with a pair of monoblox and got rid of it by running a wire from the preamp chassis to one of the amp's chassis.

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.