Classe' preamp ground loop hum. Help!

I just bought a Classe CP-60 preamp. When I hooked it up i got a vicious ground loop hum. I mean a wicked hum, like if I was running cheap speakers they would be toast. Checked all outlets on circuit, perfect ground. Disconnected everything but amp, preamp and source. Still ground loop hum. Hooked up Sony TAe9000ES in place of Classe', ground loop hum goes away. Do i just have a defective preamp? Suggestions? Advice?
Is this pre-amp new? Do you have a VCR pluged into the same outlet? Also try lifting all ground except the pre and let me know what happens. Simply Music
Simply_music- The preamp is new. I disconnected everything from the outlet and all other outlets on the circuit and still got the hum. I replaced the classe w/ first an Adcom preamp and then an A/V preamp/processor and got no hum with either. This preamp has a separate power supply. I wonder if it could be a problem w/ either the A/C cord or the power line from power supply to preamp?
Lift the ground on the preamp. The hum should go away.
Narrod- Forgive my stupidity, but is there any other way to lift the ground on the pre-amp than removing the third prong from the existing power cord or getting a new ungrounded ( two prong)power cord?
Ignatz get a "cheater plug" just two ends and yor get ground free + reverse capability for testing..
Ignatz. The easiest way to do that is just go to your walmart, k-mart or home depot and buy a cheap plug-in multi plug for about $3.00 and take a pliers and break the ground on it and plug the unit you want to lift into it but may I suggest that you lift the amp first and if no improvement then the pre but not both and if that works just get a power cord and cut the ground. Now this is all assuming that the noise is there even with the volume is down and in both channels, right? I am a Class A dealer here, you can drop me an e-mail if you would like and if the problem persists and if your dealer can't help.