That is odd to say the least. I have never had a Parasound product hum on me at all. My current HALO has been hush hush since day one. I think in total I have had maybe a total of 8 or 9 Parasound amps and they have all been fantastic and quite! My current HALO has been run through an Onkyo receiver and now my Denon 3805 and it's still dead quite.

I honestly have no explanation why some people hear a hum with these. I have owned more of these then most and have yet to hear a thing.