Interesting...

Power is provided by a Happy Ending Kit uZeus, but now that I think about it, the audio cables running between the Wasp and the mixer are draped over the top of an Emu sound module before plunging into the dark recesses of my equipment rack, where is is probably in close contact with the rear plane of several other components--notably, where the power supplies would be.

I run balanced patch cables exclusively in my rack, but of course the patch cables connected to the modular are 2-conductor, unbalanced. Since these wires run very close to several transformers on their way to the mixer, that could be the problem. I'll try rerouting the wires and see what happens.

Thanks for the tip!!