I originally had my new H390 plugged into my 20 year old Isotek Multiway. Until, that was, I started experiencing minor cut-outs. The display went black, and knobs and remote were unresponsive. The music was still playing though.
Hegel told me this can happen:
if the amp is subjected to power spike or voltage drop
Resetting was a simple case of powering off/on. Their advice was:
in general we have found that using power conditioners, regenerators, transformers etc with our amp generally tends to degrade and restrict the dynamic characters on our amps, so we would normally not use such devices unless there is a serious issue with the local mains supply
So, I bought a decent mains cable (Furutech DPS 4.1), plus QSA fuses, plugged it into my UK mains socket, and no problems since. My house is only 10 years old, so chances of substandard wiring being the cause are minimal.
Saying that, I've recently upgraded to an Isotek EVO3 Sirius for my digital sources, and am reaping the rewards it offers. I have not yet however tried the Hegel with it.