Electrically it'll work if you supply 12v to the drive separately; there may be power sequencing issues as 5v will come and go depending on whether the empeg is on or off - so you'll want to gate your clean 12v supply (THIS DOES NOT MEAN A FEED FROM THE BATTERY, THIS IS (a) NOMINALLY 13.8v WITH THE CAR RUNNING and (b) CAN HAVE SPIKES OF -200V ON IT) using the 5v supply.

The main question is *why* you want to do this. The drive is not designed for mobile use, will most likely not fit in the box, etc. I can see your point if you're using the empeg as a home stereo, sat in a component box with a PC PSU to supply the 12v, but not if you're intending to use it as a carplayer.

Hugo