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I recently installed an Alpine 40x4 amp. The amp is grounded to the inner rocker panel under the back seat, which is about a foot from where the amp is mounted. I'm getting alternator noise/whine ( the sound changes with engine speed) from all speakers.

I tried messing with grounds with no luck. I also tried a ground loop isolator just for the hell of it, and it may have helped. The remote turn on, power, and RCA wires were all run together. I read on this forum that it could or could not casue problems.

This is a old car (30 years), so the ignition system is probably giving off alot of noise. What should I do?

Thanks in advance.

there is your problem run your rcas on the other side of the car and im sure it will stop. also you can put a small .5 farad capacitor behind the alternator to shunt the noise. others may disagree with me on that but it worked everytime i did it!

I think that's the next step. Tonight I tried makeing a shorter ground cable, and there was no change.

As I unplug the RCA cables, the noise goes away, which leads me to believe the power wire and RCA cables are interfering.

When the relays for the highbeams and turn signals actuate, I can hear it through the speakers. Ground loop?

i dont think its a ground look im sure its the fact you ran them toghter. fix that it will go away. and try the cap thing i posted.

How is the Hu grounded? Is it grounded through the wiring harness? If it is, ground it to bare metal instead. Some headunits introduce a lot of noise into a system. I have found that with A LOT of Pioneer decks, they are incredibly noisy decks. But i also agree with the power wire/RCA thing. No guarentee it will get rid of the noise, but can't hurt to try.

Justin from Detroit wrote:How is the Hu grounded? Is it grounded through the wiring harness? If it is, ground it to bare metal instead. Some headunits introduce a lot of noise into a system. I have found that with A LOT of Pioneer decks, they are incredibly noisy decks. But i also agree with the power wire/RCA thing. No guarentee it will get rid of the noise, but can't hurt to try.

The headunit (Blaupunkt), is grounded under the dash somewhere. I had some alternator whine in the past, and it went away. It came back when I installed the amp.

How about the sound of the relays actuating being heard in the speakers?

Justin from Detroit wrote:How is the Hu grounded? Is it grounded through the wiring harness? If it is, ground it to bare metal instead. Some headunits introduce a lot of noise into a system. I have found that with A LOT of Pioneer decks, they are incredibly noisy decks. But i also agree with the power wire/RCA thing. No guarentee it will get rid of the noise, but can't hurt to try.

hmmmm my pioneer is grounded through the wiring harness and its fine, same with my last deck and my cousins. Someone up there likes us

Ok, I did some troubleshooting by using crutchfields advice, and it seems to be coming from my RCA cables. One set is very good, and the other set is decent. Even the very good cables (twisted $27) is picking up noise.

I also have two ground loop isolators hooked in line to the amp, and the power and RCA's run on opposite sides of the car. What to do?

and your still getting noise? do the cap thing like i suggested! it will hopefully shunt the noise... get your self a cheap high quality cap from alumapro or stinger and put that just behind the alt it should take care of it. rcas are rcas there is very little quality diffrence.

EDIT: The problem still persists. I have found a ground wire off the headunit that when disconnected, makes the noise louder, yet has no affect on the headunit.


Other than that, I'm more confused than ever.