I recently got a EHX Voice Box, also. What you describe is very similar to my experience. If I hook up the Voice Box with nothing but the microphone and the Fishman amp, it’s fairly quiet. But if I try to combine the Voice Box with any other effects, it hums like a madman. Specifically, I’m attempting to put a TC Helicon Mic Mechanic right after the Voice Box. I’ve tried various power supplies (including the official EHX AC/DC Adaptor) but the noise only changes–never goes away.

Electro Harmonix: Anybody home? Any ideas or suggestions here? Do you test your pedals in combination with other pedals? A quick search of music forums will show you that this noise problem is typical to the Voice Box.

-KR