crzunch

I used a Ground Loop Isolator, as someone suggested, no success.
Im still getting feedback, any ideas???

Bugbyte

Do you mean feedback in the rock and roll guitar style like when you put a microphone directly in front of a speaker, or do you mean a whining or buzzing noise that tends to vary with the speed of the car?

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KRS_Juan

If it's "a whining or buzzing that tends to vary with the speed of the car" as Bugbyte said, try moving the audio cables further away from any cables carrying power, or get better shielded audio cables.

-KRS Juan-

aaronle06

i get this problem bad when i have my hacked cable going through the mini to the power switch. is there any way to shield that from EMI from alternator whine?

pand0ra

So I get feedback as well and I am pretty certain that it is from the alternator. It is also limited to the right channel. If I plug in the XM radio it gets way worse. I have everything grounded, but not using the same ground. Can that be a problem?

Bugbyte

Yes. One of the causes of feedback -known as a ground loop, is caused by slight voltage differences between ground points. The car body as a ground system has differing resistance across the various ground points. It is also possible that even though you may ground to a single point, that point isn't a good one.

Check the Wiki and the FAQ for more info searching on terms "ground loop" or "whine".

__________________
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zapwizard

It does help if everything is grounded to the same point, but it is not required.
What is more important is that the ground of your audio signal (or shield) is NOT connected to the power supply ground.

You need to double check your wiring for the amplifier and the PC.
A ground loop isolator won't help if the audio ground is still connected elsewhere.
A good amp will completely isolate the audio ground from the power ground.

Another possibility is that your alternator is directly affecting your amplifier when the voltage changes. In this case a power filter is what you need. They are dirt cheap at any auto parts store. I used one before my amp and LCD (had noise) along with a ground loop isolator.

pand0ra

So I figured out the alternator noise problem. It is because I was running the power wires next to the speaker & RCA wires. Once I pulled them the noise went away. I read somewhere that you should run power wires along one side of the car and the audio wires down the other.