amp: usx4065

1&2 are hooked up to a pair of cdt cl-61s

3&4 are bridged, hooked up to an ed e12kx.

I noticed that when I have the rca's hooked up to channels 1&2, and nothing hooked up to 3&4, my sub is still getting a signal. I've verified that it really is a wire signal and not just an indirect effect (vibration, etc.) because when unplugging the wires from the box on the sub, there's no sub movement.

there's a switch on the amp that has three options:
a. 1+2
b. 3+4
c. low

I thought maybe they had something to do with it, but each option yields the same result.

I don't *think* this was happening on my old setup; however, my old setup consisted of:
- instead of cdt cl-61s, some kenwood 6x9 coaxes
- instead of my clarion HU, my dual xd-6200.

I'm using one rca wire (pair) and using a y-adapter to split to 4 channels.

anybody have any ideas???