I have a Simmons DA200S that has a distorted output if I use either the Drum input or the AUX input.  There is no distortion if I use the Line In input. The distortion is present in the speakers and in the headphones output.  I haven't checked the line out outputs yet.  Looking at the Signal Flow Diagram in the manual, I am thinking the problem is in the equalization, master volume, or the headphone circuitry.

Any suggestions of specific things to look for? Any idea how to get a copy of a schematic?

Thanks,
Tony