We have a Ramsa 1200W

Question

We have a Ramsa 1200W power amp to run our monitors for our band. We split the channels to run two sets from the mixer board. the A channel is working great. The B channel is popping, cracking and surging. I have checked all the cables and even switched up the floor monitors to make sure it would not be a bad monitor. Is it possible for one side of the amp. to be going out? Or, could this be an issue with electricty? too much on one circuit?