Owning a B&K AVP-4090, I'm very familiar with the 15ma. output capacity. I used a 12v. reed relay (which has a coil current of 11ma.) to activate a 120v. relay with 10a. contacts, which in turn powers a 25a., 4-pole contactor which control 4 of the 8 circuits in my sub-panel.

I installed an RCA jack on the front panel of the sub-panel for the connection to the B&K, soldered the two smaller relays onto a piece of perf-board, soldered on the wires, put the board inside a heavy-duty plastic pouch, and put that and the contactor inside the sub-panel.

The 4 circuits are (1) the switched electronics, (2 & 3) the two amplifiers, and (4) the sub amps. The other 4 circuits are (1 & 2) lighting, (3) the unswitched electronics, and (4) the CRT projector. Total cost for the relays and parts was about $15, since I had the contactor.