I have a rather old Logitech Z-2300 and was wondering why it hums while it's on. I have it connected to my motherboard's onboard soundcard. Is there a way to fix this, maybe a dedicated sound card?
It's a either a ground loop, which a cheater plug can fix, or an internal voltage issue, which a repair shop can probably trouble shoot. Although repair shops probably charge more per hour than your speakers are worth, unless you have a handy friend.