Thanks all, very informative. This morning I tried switching all other circuits off in the house but the buzzing remained. Only thing I didn’t do was unplug all the upstairs sockets on the same circuit as the power supply as I wouldn’t have been very popular! Will try that later though. I have a reef fish tank with LED lights and a number of pumps which I thought would be the culprit, but seemingly not.
Presumably the buzzing would cease pretty much straight away if the culprit was disconnected?
I’m not worried about the unit itself as the XPS it replaced did exactly the same.
House was built new ten years ago so wiring should be fine. If I can’t isolate it in the house I’ll try a DC blocker.
I have a very similar experience. HiCap DR buzzes like mad all the time, XPSDR was totally silent, as is my recently acquired 555DR. All behind Isol8 axis blocker…
Funnily enough I was checking some devices for electrical noise a couple of days ago, using that highly sophisticated precision instrument, the portable AM radio.
I pointed it at an iPhone charger first, just to check it was working. When I turned the charger on, the noise started immediately. When I turned it off, though, the electrical noise continued unabated for about a minute.
There was probably a little residual charge in the unit till it ran down
The led on some units stays on for ages after they have been completely unplugged