The karacter 500 gives you ultimate flexibility in terms of configuring its channels:
This gives you two fully independent channels of saturation/distortion/destruction – two units in one! This is of course the right mode to process two completely different signals at the same time. Or to send the output of channel 1 into channel 2 for even further mangling... if you dare.
In this mode, both channels are linked and controlled by just a single set of controls for comfortably processing stereo sources. The left controllers and bottom switches become the master for both channels. The obvious benefit is that you don't have to compare and match the settings of your left and right channels all of the time when processing stereo material.
This gives you the option to process the mid and the side signals completely independent from each other. Then, left becomes mid channel and right becomes side channel. You can apply a high amount of saturation to the mid and leave the sides completely untouched, or the other way round, or anything in between... Different settings of the gain controllers can be used to create subtle or significant changes within the stereo spectrum.
The linked M/S mode might seem a little odd, as the behavior seems to be exactly the same as in linked stereo mode. It can still have its benefits, though, as the inevitable divergences between left and right channel which are caused by natural component tolerances will be reduced in this mode, because here the side information of both channels is processed in a single audio path.