Words to live by, copied from the Mark III manual. "In the Rhythm modes the Volume 1
control determines the Effects Send level, and in the Lead mode, it is the Lead Master. By running the Master 1 higher and these two controls lower, you can improve the performance of sub-standard effects."
If you are an effects loop user, this will come in handy.
Also, the graphic EQ is a very nice option to have- if used in moderation. Too much adjustment of the GEQ is for a shitty guitar or speakers, in my opinion. Been playing the Mark series since the 1980's, myself. Good times!