Originally Posted by djdexta2k
Mono sound isn't meant to just come out of one side, its just that the left and right side will be EXACTLY the same, the LEFT/MONO input is duplicated in both channels LEFT & RIGHT.
There are times when this is beneficial (bass, lower frequency sounds to stop phase cancellation).
Mono sound meand the same sound on the right and left channel nor that it its panned to one of both.
Substractor is mono and every mono signal needs to be conected to te left input otherwise you wont be hearing anything...