The bass box on my version of the A200 has a small transformer mounted near the PCB which is putting out about 15VAC so probably a 12V DC rail. I am thinking of removing it from the box has as it is causing a fair amount of mains hum. It would be nice to have a circuit schematic as that zip file does not have one.You need to open that zip file, which may result in having a circuit diagram that can me examined and some useful advice being obtained. otherwise there is not enough information available to offer any useful advice. It appears that this box requires an external power source, but what that may be is not clear.
Moderator edit: New thread created from this.