unless you're doing something special...run the voice
& guitar right into the wall, and get rid of the
mini-mixer. let the soundman do his thing, and don't
try to get in his way....that's what he's there for.
the more things he can't control, the less control
he has over making it sound good....
coming from a church soundman
now, if there is a good reason for the mixer to
be there (not enough inputs to the snake
to the control room, special effects, doing a play
or something where local control is desired), then
maybe....but seriously, if you are just trying to have
control over your voice/guitar you're really getting in the
soundman's way.....