Mono/Stereo Table for the M-Series. Special Thanks to JimRyanLine6 who originally researched and created this list.
True Stereo - Left input goes to the Left output, Right goes to the Right output, effect is added to each channel separately.
Mono - Left input and Right input are summed to mono, effect is added to the mono signal which goes to both the Left and Right outputs.
Stereo Thru/Mono Effect - Left input goes to the Left output, Right input goes to the Right output, Left input and Right input are summed to mono, effect is added to the mono signal which goes to both the Left and Right outputs.
Stereo Thru/Stereo Effect - Left input goes to the Left output, Right input goes to the Right output, Left input is processed to create a stereo effect and mixed with the Left and Right outputs, Right input is processed to create a stereo effect and mixed with the Left and Right outputs.
The difference between the last two is a mono effect will sound like it is in the center of the stereo field, a stereo effect will lay across the stereo field.