I have a POD X3 bean and I've set it up to use dual tone and in the output options I've panned tone 1 to the left and tone 2 to the right. Why is it this only works when I have both output cables plugged in? When I unplug either left or right, I get both tones through one output. I'm using a 1/4" to rca phono cable which plugs into a power amp if that helps.