I do not know very much about car stereo systems at all. I am trying to hook up my laptop or portable mp3 cd player to my stereo. I have a pioneer deh-10. It has an rca input in the rear so i plugged in a cord that goes from rca to headphone jack. I can get the music to come out of my rear door speakers at a very low volume. Plus there is no way to choose aux input on my cd player. If I turn the volume up on the cdplayer i get the radio station it is set to. But if i put it on 1. I get the mp3 player at a very low volume. my plan is to build a computer to put in my car for gps, mp3, internet, and dvd. So I was wondering if anyone could clue me in on this knowledge. thanks