Master at 12 o'clock or above, Volume at 10 o'clock or above. Push the volume up as needed for more crunch. Switch on the bright for a "crispy" tone, but be careful the treble is not above 2 o'clock.
Personally, I run master a 3 o'clock, volume at 11 o'clock, no bright, treble at 2 o'clock, mid at noon, bass at 9 o'clock. This gives me huge crunch, also very loud, but still sound great.
Hope that helps.
Jim