Ok so I have a complex audio system to say the least. I will try to explain it the best without losing anybody.

I have a Pioneer Head Unit, Pioneer DSP EQ, 5.1 channel surround processor for control over a center channel, Soundstream 5 channel Amp, and a Boss 2 channel amp. I have developed a ground loop that is pretty persistent. With the engine OFF and key on I get this noise: It's the typical hum/high pitch sound but also sounds like Star Trek if you listen close. The noise hisses, then changes pitch, then sounds like a synthesizer, noise goes up and down the frequency curve and then all of a sudden will completely suppress itself for a second or two and then it starts again. It is not a repeating pattern and changes what it will do each time the Head Unit and DSP fire up. I have isolated it down to the 2nd amp (Boss 2 channel) and the 5.1 Surround Sound Processor. When I change the grounding points from the rear chassis to the passenger seat bolts it almost completely eliminates the noise but you can still hear it faintly. I also know if I turn the gains down more on the 5.1 channel processor the noise also becomes quieter, BUT that hurts the volume level of the center channel so I would rather not do that.

Ok soooooo....believe it or not I always was led to believe that grounding all sources to 1 point was a BAD idea...but it seems I have read a few posts saying to do this....opinions?

Been working on the problem for a few nights now. I really would like to eliminate the noise completely. It is faint now with the new seat grounding points...but I still know it's there.

I have my power wires running down the passenger side. RCAs running down the middle of the car with the speaker wires as well. The power lines only come in contact in one area where they must cross over the RCA's. I couldn't avoid that cause the power hook ups on my amp are on the far left side. The amp is mounted on the center rear bumper wall. Had to get the power over to there. I did test and hold the power wires up and away from the RCA's just to be sure that was not where the noise was coming from. It made no difference. My gut is telling me...it is just a bad ground loop because I have 5 sources all having different grounds. Amp 1, Amp 2, Head Unit, DSP, & 5.1 surround processor. The head unit and DSP are grounded up front on the radio bracket attaching it to the car chassis. The Amp 1, Amp 2, & 5.1 surround are all grounded in the back (cause that is where they are located) to 3 different spots on the chassis.

So if I ground the 3 big sources in the back to a common ground...do you guys think that will help? I am going to try that tonight...it is really the only thing I have not tried yet.

Just looking for ideas and opinions....

 

I think it all depends on the quality of your RCA patch cables and weather they are picking up noise somewhere along the line. I was fighting the same thing. Noise with engine off and with it on. Loud thumping in the sub too. I had the 2 amps grounded to the same place and tried 2 different ground locations and that didn't help. I figured my patch cables were picking up noise but I didn't feel like tearing the whole system apart again to replace them so I got a set of ground loop isolators from Crutchfield. ALL noise is now completely GONE.

 

Thanks...I was curious. Yeh I bit the bullet and bought an isolator last night just in case, but realize this is only a last ditch effort...I would like to try to find the best possible ground solution. I dunno maybe last nights effort is the best Iam going to do with so many components in my setup. I have to use like 3 different sets of signal cables and "Y" adapters. The main RCA signal cable is a 4 channel Monster Cable, so pretty good. The sub 2 channel RCA output from the HU is just what came with the Amp kit I bought. I tried different ones in the back. The 4 channel main cable I had to split with 2 "Y" adapters to get signal to the surround sound processor (My amp doesn't have an output section on it). Out of the surround processor I have another "Y" adapter to change the center single mono output into a dual output to go to the 2 channel amp to use for the rear speaker fill and the center channel. So yeh, I have lots of areas that are targets to introduce noise into the system but I have tried to keep within the audio guidelines to keep the noise out.

 

could it be ur cheap boss amp

 

I guess anything is possible but from the way it sounds I doubt it. Not unless the Vette has something against Boss If someone has a nice different brand amp to test I would try it but I only have 2 different amps (granted they are both Boss) and I have the same problem with both of them. I take them out, put them in a different car...no problems.

 

There are a lot of electronics going on in the C6 that can cause interference noise. The 2 amps I'm using are fairly cheap and they came out of my previous car (Pontiac Grand Prix). I had the sloppiest wiring going on in that car. Patch cables running down the same side and right on top of power cables! Believe it or not I never had a hint of noise of any kind in that car. The same setup in the Vette but going by the book and keeping power away from signal and noise was crazy.

 

If it is being caused by all of the grounds being in different locations you could try an experiment and connect a single wire between them all. In theory they're all grounded to the same frame, but that doesn't guarantee they're all at the exact same resistance. If you connected all of your grounds together it may even out the resistance enough to solve any ground loop issues. Since they are actually grounded already, you shouldn't have to worry about too much current, so I'd guess even something as small as 18 gauge should be big enough for the experiment.

 

you may have already tried this but maybe physically swapping the amps and see if the problem follows the amp or the wiring. it doesnt sound like engine noise in your description. i would guess there is something going wack in your amp, and i agree with the poster above about having cheap rca's, quality of wiring is important, most of the power wiring coming from stereo shops and flea markets is mostly aluminum and complete garbage.

it also sounds like you have alot of Y's in your rca wiring, try just running one cable all the way thru for testing purposes and introducing Y's one at a time to zero in on the faulty junction.

if switching the amps is not an option you can borrow my spare alpine v12 4 or 2 channel for testing if you promise to return it

peace!
mike

 

i would run all the grounds directly to the battery, the vette has too much plastic and fiberglass and you never know for sure what kind of ground you have.
also your probltm sounds like your getting a ground through the rca's a lot of cheap amps share the ground with the rca ground, if you install a ground loop isolator which can be found at radio shack or walmart it will electrically isolate the ground from each component. try installing one between the processor and the amp and i bet it solves your problem.