Yes, 11 o'clock is unity gain. Before that you are attenuating (don't know how much). I'm still getting use to my 9100, but I did pull a nice recording (at least to me I think it is) of Derek Trucks Band in about the same circumstances as you. I used the 9100 at 12 o'clock and the iHP140 at 0 gain. Being a louder show (I'm assuming), I would start out at 11 o'clock and work from there. Hopefully there will be an opening act for you to check levels with.