I don't remember who first mentioned the significant hum coming from their LFR1100 Actives, but that's been the case for me as well. It doesn't help that I don't have all of my equipment on the same circuit, and there's no easy way to remedy that. I read at one point it can help to have all relevant circuit breakers on the same side of the electrical panel, and I don't even have that. I still need to run an experiment at some point in which I run extension cords to some equipment so they're all at least on the same side to see if it actually makes a difference.

In the meantime, I heard someone had luck eliminating their hum with this product:

Emotiva CMX-2 Precision Common Mode AC Line Filter With DC Offset Eliminator

Seemed worth a shot for an easy solution. It arrived today, and I think I shot myself in the foot. I tried it in various configurations. Since it's just two outlets, first I did both DSPs, then both amps, then just the amp and DSP on one side. Each one made the hum worse. As one last test, I connected it upstream and plugged the AV receiver into it. Same thing. The already significant hum was significantly worse. Deciding it wasn't going to be my miracle, I took it out of the chain completely and reverted to the way I had it. Aaaand the hum has remained at the higher volume. Whereas before the hum could be drowned out with content playing, now I'm hearing it even when I'm playing stuff. Can't live like this!

I emailed Axiom for ideas, but I figured I'd post here as well to see if any of you have suggestions.