I get noticeable alternator whine when i have the volume up high, but a quiet part in either a movie or sound coming through my AUX...What is a common cause of this?

 

check your grounds,rca cables, or it could be your head unit, are your power wires run one side of the car and the rca's run on the other side of the car?

 

Whatever source you have running into the AUX input isn't properly grounded. This could be the cables for the input, or the thing itself.

 

I have a PS2, and the audio is hooked to an FM modulator, then to the antenna, and i get the whine too....it's annoying.!!

JdawgX: Would u ground the PS2 or the FM modulator..?

 

If the FM modulator needs power it needs to be grounded. The PS2 definitely needs a good ground. And proper cable routing in the vehicle. The PS2 likely has some noise of it's own. Most computers have very high noise levels. But that is different from alt whine.