Major Ground Loop Help Needed!

[B1GR3DDD]

A few days ago I asked for help on fixing a ground loop. Well, after trying a remedy, my problems have gone from bad to worse.

Here's what it currently sounds like (apologies for **** quality, had to use old flip camera, phone was full):



Breaking down what happens in case it wasn't obvious enough:

-Normal high pitched whine heard at low volumes (not that it goes away at higher volumes, it just is drown out by the increased volume)

-VERY loud and annoying high pitched whine at "0" volume

-Loud whine and thump (from subs) when car is turned off

The only way I'll fix this is isolating the problem and working backwards to fix it obviously. So I ask:

What steps should I take to find the source(s) of my ground loop?

Click to read more...

 

[big scott]

ground the rca's on the back of h/u .

it seems like a lot of pioneer h/u's do that.

 

[big scott]

look at the # 2 pic in this thread.

http://www.caraudio.com/forums/head-unit-classifieds/623277-pioneer-deh-750mp-6v-pre-out.html

also make sure the ground wire going to h/u is good.

thats the first 2 things i would do.

 

[B1GR3DDD]

look at the # 2 pic in this thread.
http://www.caraudio.com/forums/head-unit-classifieds/623277-pioneer-deh-750mp-6v-pre-out.html

also make sure the ground wire going to h/u is good.

thats the first 2 things i would do.

Head unit RCA's are already grounded. I have a hard time believing the head units ground cable is to blame, but it's on my list of solutions I plan on doing. Will probably do a 12 gauge run to a nice piece of metal.

 

[big scott]

if it has a bad ground then yes.

its in the name ( ground loop )

not sure of your h/u has a pico fuse, but if it does it could be that.

but there are some that you cant get rid of that ground loop.

but i would try everything.

even ground the chassis of the h/u to the same ground as the harness.

also you need to list what you have done.

as we can only guess.

 

[B1GR3DDD]

So far I've changed my RCA's to a better, more shielded type, grounded the headunits RCA's to the head units body, and tried regrounding the RCA's at the 4 channel and sub amplifier.

 

[wew lad 5,000+ posts]

what happens when you pull the RCA's out of each individual amp, try one at a time then both

 

[B1GR3DDD]

When testing, I was listening for the "thump" I was hearing when the car was turned off. When I removed the RCA's from the 4 channel amp's pass through to the sub amp, the thump was still audible, but less loud as the subs aren't playing it. When I removed the 4 RCA's that come from the head unit from the 4 channel amp, the thump was completely gone. Since when disconnecting the RCA's the sound was no longer audible, this leads me to believe that the root of the noise is stemming from "upstream" by either the RCA's (unlikely as I just replaced them) or the head unit (probable)

I noticed when testing while I had my back seat down that the "thump" I was hearing had a pattern to it, virtually identical to the sound of the "click off" that my 4 channel amp makes when it powers off.

 

[AnthonyO 10+ year member]

That noise at 0 is a bad output on the head-unit. Replace it

 

[Worlddre 5,000+ posts]

You shouldnt hot swap RCAs at all but especially when dealing with a Pioneer deck thats what causes that little fuse inside the deck to blow.

 

[Massive spl]

You could have a speaker wire touching somewhere. If the noise is there without the Rca's hooked up the. The problem is on the output side, so go one by one each speaker wire and with your DMM on ohm setting and touch the black prob to ground and the other prob to 1 speaker wire, the wires should read 0 unless it's touching something which is causing your Interference. Time consuming but hopefully helps you pin point your problem

 

[B1GR3DDD]

You could have a speaker wire touching somewhere. If the noise is there without the Rca's hooked up the. The problem is on the output side, so go one by one each speaker wire and with your DMM on ohm setting and touch the black prob to ground and the other prob to 1 speaker wire, the wires should read 0 unless it's touching something which is causing your Interference. Time consuming but hopefully helps you pin point your problem

The noise isn't there when the RCA's aren't connected, only when they are.