The Harman Kardon set-up is 2.1 with (2)
stereo speakers and a base(Sub).

The model number is HK695-01

The speaker plug is in the same APC surge arrest.

http://www.apc.com/shop/us/en/produc...r=SEC-756-GOO-[53166061159]-[269259981065]-S-[]

As I say, this is an intermittent problem
that comes and goes. Most of the time
everything is fine.

Robert