Does anyone have this problem? I very rarely use the rack mounted Fender reverb, but I just tried it on a clean guitar sound and found that the sound it creates is horribly distorted and fizzy, almost like it's acting like a fuzz pedal. Gets worse the more you turn up the "dwell" knob. I don't recall it ever sounding like that before. Tried it with multiple amp types, all very clean tones, yet the reverb is basically full on distortion every time. 

I'm not familiar with the plug, but in the real unit the Dwell control is affecting the gain of the circuit. A fender Champ and the reverb unit are essentially the same thing circuit wise. One drives a speaker and the other a reverb tank. The Garnet Hertzog that was made famous by the Guess Who in American Woman is also similar.
 
Perhaps parallel processing or reducing the input signal will help. 

Funny thing is though, I don't seem to be able to dial in a reverb setting that doesn't sound horribly distorted, even with the dwell on low settings it's noticeable. And my input setting is quite moderate. Perhaps I'll try even lower.