Could the MONO be the problem using a STEREO VH signal?
Nope - dirty is dirty in mono or stereo. It's cloudy and muffled in the internal speakers too. I have to face it - it's just not the best choice for a mic processor. Korg really missed a great opportunity here. This thing is no where near their usually high standards.
(is anybody at Korg listening ???? reading ???? R&D guys - c'mon - fix this !)