Most keyboards will double the "left" output jack as a "mono" jack. Will the QS output in "mono" if you just hooked up one cable from the left jack to your speaker?

I do remember reading in the manual a ways back for for the QS6.2 that if you hook up a single cable in the left (or right) output the QS will automatically route both the left and right channels to that one output. This is suggested when hooking up to a "mono" system.