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GMB · 5th Apr 2021, 2:29 pm

A big problem these days is that everything is "double insulated" which means that any wired connections see a capacitor to an average of the L and N voltages, so any such connections for simple audio have to face potentially quite a lot of common-mode mains hum, and this may include higher frequencies modulated with 50 or 100Hz too if SM PSU is involved.

I have this problem myself but haven't got round to trying what I would consider the obvious fix - transformer isolation of the audio, with an interwinding earthed screen. Or perhaps an optical isolator.

Powering your rebro from the TV would be the other fix of course.

5th Apr 2021, 2:29 pm	#6
GMB Dekatron Join Date: Aug 2003 Location: near Reading (and sometimes Torquay) Posts: 3,094	Re: Odd PSU behavior A big problem these days is that everything is "double insulated" which means that any wired connections see a capacitor to an average of the L and N voltages, so any such connections for simple audio have to face potentially quite a lot of common-mode mains hum, and this may include higher frequencies modulated with 50 or 100Hz too if SM PSU is involved. I have this problem myself but haven't got round to trying what I would consider the obvious fix - transformer isolation of the audio, with an interwinding earthed screen. Or perhaps an optical isolator. Powering your rebro from the TV would be the other fix of course.