Tim Downie wrote:
... and no, it's not because it can't remember the words. ;-)

All the time my KEF PSW2000 subwoofer is powered up, there is a constant
background hum. (http://www.kef.com/history/2000/subwoofers/sub2.asp)

Pretty sure it's just a mains frequency hum coming from its power supply (it
doesn't change whether any input is connected or not).

Does this sound like a fairly basic/simple repair job? Is it likely to be
just the smoothing capacitors in the power supply or might it be more
complicated?

I know which end of a soldering iron to hold and recognise the dangers of
big capacitors. Could I fix it myself?

Tim


Is it a gritty him or a fairly 100zh hum or a really 50hz hum..

I am surprised..how long has it been doing it, and how long have you had it?

You MIGHT have an earth loop.. unplug it and see whether the audio
input earth is connected to the mains earth.(use a continuity tester).if
so try a quick test with the mains earth disconnected...