Plug the input end of the 12V AC power cord into the Behringer MX400 and plug the opposite end into a power outlet. The green LED light above the word "ON" will light when the unit power is on.
Plug one input into each of the input jacks of the MX400 using 1/4-inch instrument cables or XLR-to-1/4-inch cables.
Connect a 1/4-inch cable from the "OUTPUT" jack of the MX400 to the input of a multi-channel mixer.
Adjust the levels of each input in the MX400 by turning the "LEVEL" knobs clockwise for a higher input level or counterclockwise for a lower input level.
Check the input in the mixer the MX400 is plugged into to gauge the level of the MX400's inputs. Adjust the mixer input and the MX400's level knobs until the desired mix is achieved.