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1995 Range Rover Classic Ground Loop Issues


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greddm 
Member - Posts: 3
Member spacespace
Joined: December 26, 2018
Location: Utah, United States
Posted: December 26, 2018 at 3:50 PM / IP Logged Link to Post Post Reply Quote greddm
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.
DYohn 
Moderator - Posts: 10,739
Moderator spaceThis member has made a donation to the12volt.com. Click here for more info.spaceThis member has been recognized as an authority in Electrical Theory. Click here for more info.spaceThis member has been recognized as an authority in Mobile Audio and Video. Click here for more info.spacespace
Joined: April 22, 2003
Location: Arizona, United States
Posted: January 03, 2019 at 2:26 PM / IP Logged Link to Post Post Reply Quote DYohn
I suggest eliminating all traces of the OEM system and installing all new. Those old factory amps (which have xover filters etc built in) are far more trouble than they are worth. Just can it and replace with a fresh new system. You’ll be glad you did.
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greddm 
Member - Posts: 3
Member spacespace
Joined: December 26, 2018
Location: Utah, United States
Posted: January 03, 2019 at 2:32 PM / IP Logged Link to Post Post Reply Quote greddm
Thats exactly what I ended up doing. I wasted 3 days trying to get it working and realized in that time I could have easily installed completely new system. Part if it was pure stubbornness, just wanting to get to the bottom of a problem. Anyway, the new 2 amp system is in and sounds great, so yeah I should have just done that to begin with...

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