Hello lovely DiS folk, can one of you help me out? When I turn my speakers on, they make a really loud humming noise. It's just as loud whether the volume is up full or on mute. If I try playing music through them, none comes out - just the loud hum, whenever they're on.

Do you think it means they're broken or is there something I can do? I vaguely remember this happening before and I think I got it sorted, but I can't remember how.

(Before you get all LMGTFY, I have tried googling, but I haven't found anything useful yet)