I hear an alternator whine, a constant ringing sound (stays the same no matter what volume), and I hear pretty much any electronic I use (like power windows, lights)

Heres all the troubleshooting I did:
- noises still there even when engine is not running, except for alternator whine of course
- none of the noises are audible if I hook up my headunit up to a mixer and listen thru headphones, so head unit does not seem to be producing the noise
- with the RCAs unplugged from the headunit, but the amp still on, there is no noise at all from just the amp feeding the speakers nothing
- I played music from my phone by directly hooking it up to the amp, with everything else on, head unit, subs. There is no noise at all.
- noise does not seem to be coming thru my subs. Hard to hear high frequencies of course, but theres no thump when I roll my windows up or down, like there is in the mids and highs. Plus Ive had the sub for a while with no noise, noise just started when I installed the 2nd amp for mids and tweeters

So since I can play music directly to it with no noise, and the headunit output does not output any noise to headphones, then it seems to indicate its the RCA cables. However, I just bought some new shielded RCAs today from Radioshack, and hooked them directly from the headunit to the amp, without snaking the wires anywhere, just straight back, not crossing any wires, and theres still noise. The old cables were brand new, shielded, from Radioshack as well, only a few days ago.

So maybe its a head unit or amp ground problem? I did ground my new amp (for mids and tweeters) to the same grounding bolt (on the chassis) as the old one. But both the amp and head unit work fine, until they are connected together. The head unit is just grounded through the factory wiring harness. There was no problem before adding the second amp though.

Forgot to mention.. They also pop pretty loud when turning off the engine, removing the head unit, or turning off the head unit. Louder than the normal quiet sound you may hear.

 

Imma take a guess at either head unit ground or bad rca connections or both. Just a guess, i'm much better at troubleshooting hands on.

 

I would try regrounding your head unit.
If that doesn't work, it could be the deck itself.

You said it just started when you installed the second amp. What happens if you remove the second amp? Does the noise go away.

What type of equipment are you using?

 

I'm thinking head unit ground too. My last head unit seemed to be ground fine though, through the wiring harness as well. It was a Pioneer deck before, and now I have an Alpine deck. Pioneers are the ones that are supposed to have problems with the pico fuse blowing the connection for the RCA ground. Both were the lowest $100 models at Best Buy. I'm gonna look for a good spot to ground the head unit to. I couldn't seem to find a factory spot last time, and I don't have a drill or sheetmetal screws right now.

I don't see how it could be the RCA cables, if I can leave them plugged into the amp, unplug them from the head unit, and there's no noise. I can also unplug them from the amp, leave them in the head unit, and there's no problem. Also, I can hook an ipod straight to the amp, using the same RCAs that run through the car, PLUS some couplers, and there's no noises at all.




My subs and amp are Alpine. 4x6s and 6x9s are Kenwood. All were fairly low end, but I didn't want to go cheap either. At least they're decent brands. Everything was bought brand new. The Alpine deck I just got was also brand new.

The new amp is a Legacy though, given to me by a friend. I was gonna try swapping it for another amp, but it works fine when an ipod is connected to it, with the same RCA cables, with everything else on, so I don't think it's the amp. The sub amp works fine and plays the head unit output with no noise, while the second amp plays the song from the ipod with no noise.

If unplug just the RCAs from the back of the head unit, leave everything else plugged in, and listen to the head unit output through headphones, there is no ground problem in the headphones. (or thru the subs that remain plugged in).

I'm pretty sure there's no noise at all in my sub, with or without the second amp plugged in. Because I would hear the thump from the electronics that I hear when my second amp is plugged in.

So the head unit, the second amp, and the RCAs seem to work fine by themselves. It's only when connecting the RCAs from the head unit to the second amp, that any component has the noise.

 

I think it is the head unit ground. It makes sense, since I have an Alpine now, so its definitely putting out a higher level signal.. I had to turn down the sub to compensate for it. That means its drawing more power and needs a better ground than it needed before.

So anyway, I used 16 gauge instead of the 18 gauge it was using. I grounded it to the same spot, sanded more on both sides of the connection, and it definitely sounds better. Less of the constant ringing, a lot less engine noise/alternator whine. Still there though.

Theres still a loud low hum, but I think I figured it out. The ground wire has been sharing a spot on the chassis with another wire. Some brown wire that is ziptied to a red wire and they both go under the hood. So I think once I give it its on dedicated ground, it should be fine.

Is the black metal under the steering wheel a good spot to ground the head unit? (After sanding the paint away of course). I couldnt find an easy spot right behind the head unit. I wasnt sure what was just a piece of metal, and what was actually connected to the whole chassis.