"The amp is standing on a a piece of plywood which is fixed to the bottom of the case. It's held in place by a strip of wood on either side and a metal clip. This means it can be easily removed when the batteries need replacing. A 12-volt transformer is plugged into an outlet fixed on the back of the case. A problem at the moment is that plugging the amp into the mains power source overrides the battery so you have to remove the speaker to switch from AC to DC. I'll have to work away around this at some point. In the meantime the battery life has been very good."
The on/off volume control has been removed and attached to the back of the Mac so the amp can be controlled from outside the case.