Linkweitz LX mini and Wyred 4 Sound mono amps -issues?

Amongst way too many other projects I have a pair of LX mini's that first I didn't have the room/placement for and then a friend loaned me his 521.4's to use and that de-motivated me from starting the mini's. So loaned the un-assembled mini kit and four Wyred 4 Sound mAmps ( mono amps) to my friends grandson. He's got them done and they don't work with the mAmps -he can feed the miniDSP x-over into a stereo amp he has and each channel sounds great -but no go with the mAmps -muffled distorted sound when he tries to feed them from the mini-DSP crossover. I last used the mAmps four or five years ago to drive my SEAS A26's -they worked fine then . I'm wondering if the miniDSP x-over requires a common ground for amp inputs ?