I use the sony switch fo listen to my CD when the empeg's not in the car. I posted a description of the wiring here: http://empeg.comms.net/php/showflat.php?Cat=&Board=install&Number=29400&page=&view=&sb=&o=&vc=1

One of the channels takes precidence over the other so if they're both powered the first channel will play.

I don't know where you can find one now though.

-Zeke