mattsimis

I tried a Common ground approach, the issue is the Line Level inputs from the head unit to the Amp are already on a common ground, presumably happened somewhere behind the head unit.

The only inputs to the Amp are:
LF, RF, LR, RR and 1 common ground.
I also tried making all the negatives on the outputs to the speakers common, that didnt work well at all!


So what I did was my plan b, bought two (2 channel so 2 units required) ground loop isolators and wired them inline with the Line Level inputs. As they are far too big to fit behind the head unit, I put them on the AMP in the trunk's input.

Connector Pinout with wire colours is here (AW article):
https://www.audiworld.com/tech/pix/connector.gif
Amp view of pinout:
http://www.a4mods.com/pics/stereo1/AmpHarness.jpg

The grounds to the Isolators are running from the single common ground input. I bridged the grounds on Left + Right on both front and rear (not sure if this was required, bit again it expects common grounds).

This worked and stopped:

-All Popping
-All engine RPM related whining

If you just put one Isolator in (front or rear) you get louder popping on the other side and much worse engine whine through the speakers. Im not sure why Ground Loop Isolators were said not to work in some of the threads I read on this, they worked perfect and totally as expected for me.

that_tg

This is great news. I have wondered why I get all the engine wine and popping. Do you have and picters of the job?

mattsimis

Well, as I knew no one could see it and its freezing outside (litteraly) I did a very rough job of it, its not very photogenic! Basically you have 5 wires to snip and splice on the connectors in the trunk; 4 channels (ie Left Front, Left Rear etc) and the one tiny common ground wire.

On the Ground Loop Isolators (GLI) I tried they were both using RCA connectors. Just connect or solder the Channel (ie Left Front) to the central pin on the RCA and then connect the common ground wire to the outer part of the RCA connection. You could then daisy change all the grounds off that initial one RCA plug connector (note I chained the 2 fronts and 2 rears independently, not sure if it matters).

For the rears I went to the Electronics store and bought some RCA plugs you wire you yourself so I didnt have to butcher the GLI's RCAs like the first one (where I just soldered wires straight to the connector).