you might wanna try using some sort of "choke" AC filter, ...... i had a problem similar to this, i was getting AC noise through the PS, i picked one of these handy dandy Isolaters, "a choke and some capaciters..."
Walmarts AC filter try adding that between your Audio out and in on your AUX adapter, Thats the best i can explain it, i suck at explaining things o.O