If he tied the amp/antenna remotes together, then he probably tried to tie the RCA outputs together, too, which might account for the problem he had where his RCA outputs did not work correctly either.

My big worry is that he didn't really specify whether he tied the car stereo's *amp* remote to his empeg, or its *antenna* remote to his empeg.

The antenna remote from his car stereo might be one of those that's designed to power an amplified antenna, in which case it might put out quite a bit of wattage, so it wouldn't be much of a surprise that it fried something on the player.