Judging by the picture the input wire looks to only be a single conductor and with a braid shield
around it . How the XLR connector is wired at the mixer should be checked out. Pin 2 on the XLR goes
to positve + , pin 3 on the XLR goes to negative - and xlr pin 1 goes to ground. sometimes the ground is disconnected
at the amp to clean up hum or grounding noise issues.
For an unbalanced input connection the way the amp is wired now would be correct.....depending how the connector at the mixer is wired. Use proper cable and wire it for a balanced input. How far away is the mixer from the amp.
There is no return on a balanced line connection, both the + and - carry audio signal of opposite polarity.
How a balance line system works is another topic all together.
Those dip switch settings are for the QSC CX series amps and yes I knew that, I use and set up many QSC's
