troubleshooting ground loop

[americannight 10+ year member]

I'm troubleshooting some noise in my volvo S60 system. Curious what you guys think might be the culprit. I'm leaning towards a HU ground loop as the cause here with the solution being, I suppose, to ground the HU in the same spot as my amps, which is all the way in the trunk of my vehicle and in a spot that is not easily accessible without removing a ton of my system to get at it...lame.

To describe the noise, I discovered this listening to the car stereo in a really quiet area, which happens to be my garage at 11:00 at night on a Wednesday //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif The noise is really faint and a high pitched whine, sort of like you might hear on an AM radio when you're in between channels. Happens when the car engine is off or on, doesn't matter. I hear it through the fronts, mainly, but if you put your ear right up to the subs which are on a different amp, it's there as well. Unplugged the RCAs from the fronts amp and the noise is still there. So I think that tells me this noise is either coming in via the power, i.e. a ground loop, or is somehow being induced into the speaker wires. I doubt the speaker wire as the culprit, however, since like I said, you can hear it faintly through the subs and those just have a short wire going directly from the amp to the subs, not near any other electrical wires. The noise does NOT get louder if I turn up the volume. The noise is still there and same level with volume all the way down or all the way up. It stays the same level regardless. The only piece of audio equipment not grounded to a bolt near to the battery in the trunk is the HU.

Curious what you guys think. If you would agree that a HU ground is a likely cause, must I really run a ground wire all the way to the trunk or would another solid ground location somewhere more easily accessible be OK as well? I could easily get a ground wire to a new bolt under the rear seat and sand down to bare metal there. That's not in the trunk but it's close.

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[CrossoverOre 10+ year member]

are your fronts seps or coax? is seps where are the xovers located? what if you unplug the rca's to the fronts do you still have whine coming through the subs? I would probably try regrounding your amps a little further away from the batt itself. Its could be theoretically grounded to a spot that lies directly in path of a component of the vehcile that is causing the whine.

 

---------- Post added at 03:38 PM ---------- Previous post was at 03:37 PM ----------

 

also try the sticky for gound loop fixes.

 

[robert420 10+ year member]

dont run a ground wire from the hu all the way to the back with the amps... bolt it to a differen, sturdy ground in the stereo slot area