I have a 2010 Silverado with some amplifier noise. It is only there when the engine is running. It is a high pitched whine, but it is not changing with the engine speed. It just kind of moves in and out. You can hear it at low volumes. It is not really loud, but it is noticeable. I am using a Kenwood head unit, Kenwood 4 channel amp, and a JBL amp for the subwoofer. I have good grounds for the amps. I am pretty sure the noise is on the low level inputs from the head unit to the four channel amp. I played my iPod back into both the front and rear amplifier inputs with the engine running, and no noise on any channel. The power cable for the amp is on the passenger side of the truck, and the signal lines are running on the driver side. Any ideas on this?