I don't have any detailed info about why you shouldn't run an unbalanced signal into it, but I have heard a number of times that it's a major issue with a Distressor and that you shouldn't do it.

Maybe do a search over on the Gearslutz forum.

Both the balanced and the unbalanced can be use at the same time but you can't take the Xlr output and short pin3 to pin1 for unbalanced. You have to use the 1/4 " output. Can't remember the exact explanation but I think that there is an amp for each leg on the the balanced out. Bringing pin3 to ground shorts out the amp. End result, it sounds like crap. The Smart Research C2 has a similar issue but has pin lift switches for unbalance use.

Thanks guys. I guess I'll just run a direct box on the 1/4" input for now till I find out for sure.

a direct box will change the input impedance going to the distressor. you don't want to do that. you can't hurt anything by just plugging the wire into the input and listening to what happens. if you use a tip/sleeve 1/4 connector it should work