The power amp in a rehearsal room was bridged to mono because of trouble with one of it's channels. The M20d is connected to it via Left/Right XLR. Is there a setting on the M20d for the Main Outs (XLR) to be converted or panned up to mono? If not, can I unplug one side and M20d will know to sum any stereo signal (such as Aux In, or Keyboards) to mono out? Any other suggestions to resolve? (other than fix the channel ^_^ )