Okay guys, I need a little help with this one.
Old head unit: Blaupunkt something... its a couple years old, just a basic head unit.
New head unit: Pioneer 7200

I used to have this annoying whine that would come through my MP3 player, and now I don't with the new head unit. The changes where I went from a head phone type plug on the head unit end to a RCA end on the incoming signal. The head unit was wired a little better, but not a lot.
That is about the only change... any ideas?

 

Did you by chance have the mp3 player plugged into the cig lighter? you might have had a ground loop that is no longer there. had the same prob with mine

 

Nope, no change there. My MP3 player is also a computer, so that goes through a power invertor which is hard wired in. But that dind't change.

 

Oh yeah. I think we were a couple of the first guys on this board to do that. mines long gone now though.... I still know what you're talking about. i think there is some sort of difference between the grounds used for the RCAs and the 1/8" jack. It sounds weird i know, but i've had the same problem.