Alternator whine

Try purchasing a "ground loop isolater", when your head unit and amp are grounded in 2 diffrent locations the diffrence in volatage to ground between the two will cause interference.
Check the below link for more details, can be purchased of a shelf at you local radioshack
http://www.radioshack.com/product/index.... loop&parentPage=search

Hope this helps
L8R

I have an alternator whine also i've checked, double checked, triple checked my wiring i've put in ground loop isolators, inline power filters with the alternator, i have 2 amps one is a brand new alpine 2-channel, tried new rca's, vehicle is a 07' chevy silverado classic any suggestions

i had the same problem. already rewire my whole system, but it didnt work. the only point of failure in my case was my HU and amp. since its easier to change the amp, what me and my installer did was try a known-good amp. several known-good amps. and all amps didnt produce that annoying alternator whine. so what i did was have my amp checked. after 2hours of repair, alternator whine already gone. the one who repaired my amp said that during the amp istallation, the (+) cable touched the body of the amp while the (-) cable is already connected to the amp. that caused one of the components inside the amp going bad. might as well have your amp checked. i can bet my life its the culprit on your case