Help needed with subwoofer problem

[Axel]

Very strange though.
I changed the mains cable to the original continental one (with an adaptor) and it went away for about an hour.
No its back, but a lot quieter. Just a varying 'rumbling' sound like a distant storm. Very audible when no music is playing.
Could it be something to do with the mains?

If you suspect a bad mains supply, listen to it in the early hours of the morning, when there is less draw on the mains and see what you hear. I mean hear what you hear. I mean....well you know what I mean!