Printer Friendly Forum Posts - 1995 Range Rover Classic Ground Loop Issues

Ok, lets start with some background info. I purchased this range rover not running. I rebuilt the engine, then moved to restoring the interior. My first order of business was to fix the horrible hum coming from the speakers (2 sources, alternator and some kind of interference) – when I pulled out the aftermarket deck, a past owner had done a hack job on the wiring. I wasn't too worried because I used to install stereos and so i'm pretty familiar with 12 volt audio. I badly underestimated how hard the task would be - rebuilding the engine was a cake walk compared to fixing the stereo thus far. Anyway, thats some history, now more details about what i've tried:

ABOUT THE FACTORY SYSTEM
This was a very sophisticated system for the time and is actually still very impressive even in it's current state. The system consist of the head unit (long gone), with 4 common ground leads in a shielded jacket that runs back to the factory amplifier, which I believe is 8ch. From the amp, we have the standard + - running to the speakers: a DVC subwoofer, 2 rear full-range. Up front there are 3 speakers in each door (Woofer, Mid and Tweeter.) The mid and tweeter are ran in a series.

WHAT I'VE TRIED
It's hard to describe just how bad this hum is and thats just with the car in ACC. When I start the engine I get the hum plus the alternator whine.

1. I ran a new, heavier gauge ground to a solid piece metal

2. Ran a new switched power supply with heavier gauge wire (factory one does not work and I was unable to trace the problem, the previous owner had done a really terrible patch into another source)

3. Converted the common ground outputs to RCA to connect to the head unit RCA outputs

4. Added to ground loop isolators to the RCA outputs (this actually made the sound worse and I currently have them removed)

This decreased the hum somewhat but it's still fairly noticeable. It also did nothing to help the alternator whine. I'm at a loss. I have two amps from a car I no longer have and I can bypass the entire factory wiring, but that is a ton of work and may possibly open another can of worms.

Does anyone have any experience with this vehicle? The Range Rover forums say it's "impossible" to get rid of the hum but I'm having a hard time accepting that as fact.