DSP Amp causing battery drain

Have a 95 740il. Have been trying to locate the source of battery drain. Took it to dealer for diagnosis. Located it to be in the DSP amp. Unplugged the amp and no more problems with battery drain. Have the amp out and need a schematic for troubleshooting. Got any suggestions where to find one? Any sugestions where I might find another amp besides salvage/junk yards? Thanks.