That is funny, yesterday I have recieved a s/h Aethos from the UK here in Germany. A very, very decent amp. But I noticed a slight hum from... the left speaker. Not volume dependent. It is hardly audible from the distance. But it is clearly there. And it is much more audible (and annoying) over headphones, left channel too. I have disconnected all sources and speakers and checked several headphones, main cables and sockets. No difference: hum on the left headphone channel. A bit more over a Grado GH2 than over a AKG K712. I guess I should contact the dealer first and send it to my local hifi garage. Or to TAD Audio, wich is the Rega distributor for Germany. My Rega Elicit mk2 is dead silent, by the way.