I have been chasing this issue for a very long time... I have alternator noise through my speakers.
Today I hooked up rcas into my amp from another car with mine running.... no noise. So I figured okay I have 3 issues it could be, deck, rca's, or power/ground on my deck.
So after hooking up the rca's from the other car I ran new power and ground to my deck, turn the car on, still have noise. I ran a new twisted rca outside the car, still.... noise. I disconnected the rca from the deck completely..... lots of noise. WTF
I have grounded everything you can possible imagine, and they're all solid..... I put in a ground loop isolator on my power and ground wire the other day. I'm out of ideas, I've spent hours trying and retrying different variations of what could fix it. I've redone my system setup so many times it's getting old.... please help