Hi, If found this on page 104 in the Main manual:
Monitor Volume Pedal (MIDI Control Change #73)
“Monitor Volume” is a special additional pedal option to control the volume of the MONITOR OUTPUT as well the internal power amplifier of PowerHead and PowerRack. It allows you to generate controlled feedback through your monitor cabinet.
Can somebody tell me if this will only attenuate the volume of the Monitor out (and speaker connected to the internal power amp), or will it also control the volume going through the Main Out's (to the P.A. sytem) ?