rich2k4 - you've said you are listening through the audio of your interface. Do you have a Focusrite interface? There hare been numerous reports on this form of poor audio out from Focusrites.
Just for the sake of establishing whether it is the Kemper or the audio interface, have you tried plugging into the Kemper headphone socket directly? And then after that, as suggested above, try running audio into the alternate input.