MainStage 3 / SL 64bit - mono channel possible?

[redbrooklyn]

I seem unable to get SL to work in a mono channel in MainStage 3.
SL shows signal on it's output meter but no sound and nothing on the MS channel meter.
Works fine on a stereo channel.

Any ideas?

using SL 1.7.3 / OS X 10.8.5 / MS 3.0.4

thx,
r