Ok, after about a week of trouble with the alt noise i finally fixed it! Hopefully this way will work for others. Ok, not sure if you need one b/c I was soo happy when i got rid of the noise to check. --A ground loop isolator, works on speakers but don't try to use on subs, you will get NO output. Ok now to the real deal....I put the ground loop filter closest to the amp (not sure if it makes a diff being behind the HU. Ok, then the noise was still present but lower. Next I put speaker wire BETWEEN the rca's behind the HU, and grounded them. Guess what, noise GONE!!! Now i'm ridin with my amp'd speakers and subs sorry, about the double category didn't know which category this belonged in.
sorry, about the double category didn't know which category this belonged in.