> It could be some "ground loop" problem, including capacitive coupling
> through the wall wart.

I realise that's a possibility. Up until now it's been running hum-free on =
a
12V SLA, which it will need to do if mains fails. Of course the knee-jerk
reaction is to blame the elephant-in-the-room 50Hz supply

Which it may well be, but I will investigate re-wiring, such as a common
ground point. I want good sound so won't be arguing with the circuit to
see it my way. However it gets done ........

For the time being I'll have a quick try with a jacked-up 7808 and see if
a flat 10+V is hum-free

Thanks

Joe



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