Okay, I know this is going to be a dumb question... I just attempted to connect my Helix Stadium XL to my Powercab 212 via the XLR cable, but I am getting no sound from the Powercab. My guitar volume is up, my powercab volume is up. When I pull up the mixer section in the Stadium it is showing sound on the meters. But nothing is coming out. On the ins/outs under XLR out level it is set to line. What am I doing wrong?