#1 sub out on my Mackie 1604 vlz Pro died today. Don't know why. If I press the "ASSIGN TO MAIN MIX" button above its fader, I can hear it in the mix, but if I listen at the actual sub out on the back, there is no signal. #2 works fine, but #1 just won't make any noise. Any idea what could be wrong? Thanks, Lava