My son wanted to be able to play his iPod through his 2005 Mitsubishi's audio system, and he'd heard that those FM gadgets didn't work well in some cars, so we decided to add a normaling jack to the audio from the CD player -- when the plug was out, the CD audio would go wherever it goes, and when the plug was in, the ipod audio would go there instead.
Opened the radio up, and found a nice flat cable between the CD player and the main board, with traces going to the connector in the player labeled "LCH' "RCH", and "ACom". So that's where we cut traces and wired in the normalng jack.
Problem is, it didn't work.
Whether the plug is in or not, the CD audio is all that comes through; nothing from the iPod comes through -- that is, inserting the plug has absolutely no effect. Buzzed everything out, and the wiring is just fine. Looked at the LCH and RCH traces with the DVM; both appear to be carrying audio when a CD is played, as expected. Actually removed the added wiring, but left those two traces cut -- CD audio still came through just fine.
On the main board, "ACom" goes to ground, and the *only* signals in that cable passing through capacitors are "RCH" and "LCH"; the rest seem to be resistively terminated, and using the DVM, they all show the sort of AC voltage that you'd expect from a digital bit stream -- no other traces in the cable appear to be carrying analog audio.
So what's going on here? Is the radio actually getting a digital stream from the CD player? Because it's pretty clear that those two "audio" streams aren't doing very much.
Isaac