I've all but given in with my car install. Its a 91 CRX, but I have run new power and ground wires (8awg) to the stereo location in anticipation of a later dash PC install.
Try as I might I just cannot get rid of the ground loop problem. It's serious enough to make listening to music unbearable even with the engine off!

I have tried both my empegs and all three sleds, the OEM stereo wiring and my new wires but it does it for all combinations.

I just dont seem to be able to encourage the ground to follow the path back to the car chassis. Hell, even connecting the empeg ground directly to either the amp or battery ground doesnt work either!
I dont think its the emepg at fault, and the amp is known good from a previous installation (I swapped out for two different amps inc a brand new off the shelf one, no change).
The battery is grounded with three 4AWG wires, one to body, one to engine, one to alternator.

If I disconnect the ground, the empeg still works and grounds through the RCA's, but reconnect the ground, switch on and off and the noise is still there and still the same level.

Now if I put some ground loop isolators inline with the RCA'ss then no more ground loop noise, but I honestly feels that is a cop out, plus $5 isolators on a $1000 stereo system doesnt make me think of quality.

Having read 99% of the FAQ's here and elsewhere, tried just about everything, has anyone got any ideas on how I get the damn thing to ground itself through the ground wire???

If this thing is grounding through your RCA's power-wise, then it is a problem with your amplifiers.

I have had ground loop problems particular witht he Empeg that I did not get with my Sony. I did have a few issues with my new Clarion, but i worked that out. I recently re-installed my Empeg and found that while I grounded the Clarion along with my 2 amps to the battery I had to ground the Empeg to the stock ground wire to quiet the system down. To make matters worse, the noise gets relatively louder when i turn the headlights on.

Now, the Miata that I drive has the battery in the trunk so i am thinking that the long cable from the hood alternator to the trunk battery causes some funky electrical issues!

But...It is bearable now and takes some work to really hear the whine..

In your case...I would just use the isolators and not tell anybody!!!!! Just let it be and enjoy the Empeg.....

You said it makes noise witht he engine off? It's not alternator whine then, which is the case almost every single time someone has an issue. You have something very unusual, and I wouldn't be terribly surprised if it is the empeg itself.

Have you hooked it up with the 120 power cable and a set of RCA leads into a home stereo? Still have the noise?

Are you sure it's a ground loop issue?

When I had lots of nasty noise with everything else turned off, I cleaned the docking connector with electrical contact spray and it worked wonders. (Maybe this should be in the "noise" section of the FAQ if it isn't already).