I’ve noticed a low level buzz when my amp is on – it’s coming from my left channel speaker only, regardless of whether the volume is off or the mute on. I
It can only be heard if one puts one’s ear near the speaker – doesn’t appear to affect the sound overall.
This sounds like some minor transformer noise being picked up by the power amp stage, the left channel may be slightly closer to the transformer “field”.
I had something similar with a SN2. I tracked it down to a cordless phone on top of the unit (there was a shelf in between it and the amp but it was still interfering). A sheet of aluminium foil under the phone fixed it
It’s a lovely look true! Considered that, but it’s the best place for it for other reasons. I’ve put the foil underneath a small covering and I now can’t see so can’t get annoyed by it