This issue has been discussed several times, I think. When we've been recording our latest EP, we tried out different settings, way too loud, very low. We always tried and tweaked and ended up with Master round 10-11, (Channel round 12-13) which was still way to loud to stay in the room. But that setting delivered the most defined and best amount compression with still open Sound. Very raw and mean, but not too heavy. Cranking the master ended up in an over compressed sound with less definition (as possible with the V
) ! In rehearsals I normally have my MV on 9, perhaps 10, with Channels round 10-12, Ch2 13 o'clock. On stage it depends on the room, sometimes the master is more to 11, but mostly round 10, and I rarely adjust the Channelsettings. Due to different cabs I usually have to alter Mids and Presence.