Sound waves are naturally round and smooth flowing.
Clipping is when the amplifier can no longer sustain that smooth wave (when the volume is too high) so it begins clipping the top and bottom of the wave off. The reproduction that is clipped sounds distorted and generally dreadful.
Just for the record, my gains are set at next to nothing.
Remember that the gains are a sensitively controller, not a volume knob. The higher the sensitivety, the more interfierance, hiss and whine make its way into the system as well as sound. :(