Sorry, but a big "Ewwwww YUK!" to the designers.....

Move the volume pot way-away form the mains wiring, mount it into a seperate box somewhere else in the cabinet...

Try and pull most of the speaker wires away from the mains wiring loom...
If you leave wires in the same loom (parallel to eachother) you'll get hum probs.

Running the speaker cable perpendicular (90degrees) to the mains wires will attenuate the hum greatly.

I realise most manufacturers were cost-cutting, so there's plenty of short cuts and industry No-No's with their electrical/electronic/pcb designs.

For best practice, you'd want to keep your mains wiring as short and limited as possible in the cabinet, and keep mains on 1 side of the cab, and audio/data wire on the opposite side.
This will greatly reduce interference probs.

MM.