Can the Channel 7 knob on 8uap be turned off?
Almost there. You need to set -100% 2 times. Once with CH7 knob to the right of center and once with it left of center.
CH7 CH7 (Make sure you see the tiny ON symbol)
-100% -100%
LINK OFF
OFST 0
SW-X NULL (set whatever switch you want. NULL makes the mix independent of the switch position)