Hey Science I may hav posted this already.Im still learning the computer. But try to take one of your RCA's out of the mixer. That will even it out for the MPC. With both in it gives a low or airy type of sound. Play around with it.
it will work but you dont need all that cable. Go to radio shack & pick up a y cable(at one end 1/8 plug, the other 2 rca regular phono plugs). Then look for these rca - 1/4 adapters. They come in packs of 2(the mono do) stereo come in packs of 1, so its up to you. But the adapter has one female end that connects directly to 1/4 & there you go. I have this set up myself but for monitors. It works just fine! Check it dude..they also come in mono.