Unfortunately the service manual doesn't help here - the BC2 is from the newer era where you're only supposed to replace complete modules instead of real service. It doesn't have schematic diagrams, only instructions on mechanical work and coarse block & wiring diagrams.
So, the only way to find out would be to take a look at the actual sound engine module and see what's installed on it... (and don't ask me, I haven't even seen the complete unit!).