Yes, its another thread about alternator whine.

Heres the system I am currently installing:
Exile S400.4 - 4 channel
Exile S500.1 - monoblock
Kicker CVR 2x12" in kicker factory box
still using OEM door speakers for now
OEM head unit
This is in a Chevy HHR, so the battery is already in the back right under the amps, so they are both connected directly to it, positive and negative.

So far I have cut into the rear door speaker wires at the front of the vehicle, and run them to the back. At that point I had them going into the high level inputs.
I have tried out both amps this way one at a time. I tried the combos of the front speakers off the HU and the sub box off the mono amp, rear doors disconnected. Im just a beginner, but it sounded clear and loud, sub hits well.
Then using the 4 channel to power the rear doors and the sub bridged while again running the front doors off the HU. I was really pleased, still clear and I liked the rear fill, so this is how I would like to run it. All well and good so far, with the car running and without.

However I am now wanting to run both amps at the same time, so I need to chain them using RCAs and a LOC. I picked up a freebie 2 channel LOC from a forum member and have one set of RCAs from the wiring kit. I also have various other sets of home stereo RCAs that I have tried.
So I took the rear channel leads out of the high level inputs and attached them to the LOC, then plugged that in to the 4channel amp, and used another set of RCAs from the 4channel RCA output to the monoblock input.

Heavy alternator noise was the result. It is fine without the car running, but as soon as I start the engine, there is a lot of background noise that varies in pitch with engine speed, but the volume seems constant. If I really crank the volume the music overpowers it, but it is still there. The part that really bugs me is it happens even when the HU is turned off. I grounded the LOC and tried various sets of RCAs, I tried just the 4 channel amp, no change to the noise.
I read on here that I could try grounding the RCAs, so that means just a jumper wire from the outer ring of an RCA plug to ground, right?
Other than that, Im stuck. Any help or suggestions of what to try next?

 

try turning the ampifier gains down...
some ppl will frown, but see if you can borrow a cap for someone.
it might filter the noise out.

 

The gains are already pretty low, matched to the output of the head unit on the fronts.
I just tried wiring the LOC up to the mono amp and sub, still got the humming.
At this point Im suspecting the LOC by process of elimination, but dont know much about car audio.
Question: would a ground loop issue between the HU and amps show up as a hum through an LOC, but sound clean using speaker level inputs?

 

Try this. Disconnect all RCA's from the amps. Take a cd player, not a pioneer, and temporarily wire it up at the amplifiers. Reconnect some new rca's and test for noise.

 

OK, tried another source using RCAs direct to amps, the hum was gone.
Could still be either the LOC or ground problem from HU though, right?

 

Run new rca's from front LOC over top of seats to amps. No noise = rca cable grounding out somewhere under the carpeting. Noise still = bad LOC.

 

Already tried 2 or 3 different sets of RCAs, they made no difference. Anyone in GTA have a tester LOC I could try?

 

Do yourself a favour and get rid of the basic crapola LOC and step up into a proper interface adaptor. A interface adaptor is going to bring your system to life. The Audio Control LC6i would be ideal in this application.

 

Bring it by my place and I will fix it for you.
Send me a pm.

Cutra