I had hum/noise issues with my phono rig that came to the forefront a few years back when I switched pre-amps and had to add a step up device to match my low output Denon DL103R to the new pre-amp (ARC sp16) phono section inputs. Location/orientation of devices and wires affected the level of hum. The source is most likely nearby power transformers, most likely mostly from teh outdoor heating and AC units on teh other side of the nearby wall. I solved the problem by placing the Electrocompaniet step up device I use inside a cylinder of mu metal foil. Its been dead quiet ever since.
Non of the speakers I had attached were high efficiency which would make the issue even harder to resolve no doubt.
Non of the speakers I had attached were high efficiency which would make the issue even harder to resolve no doubt.