This is due to your amplifier not having a capacitor blocking high frequency
noise from other noisy appliuances connected to the same ring main.


There is no easy answer to this it can often happen with fridges also.

The best place to start is with your hifi.

Regards

Jim

"Pinot Grigio" pinotgrigio@somewhere wrote in message
...
Whenever we turn a light on or off, an electrical sound can be heard from
the PC speakers.
I assume we have a faulty connection somewhere.
Any suggestion as to the best place to start. Is it more likely to be the
lighting circuit?
I suspect the answer is that it could be anywhere but just thought I'd
ask!