I bought some Logitech X-530 speakers from Dick Smith yesterday for my new Mac Mini. It sounds great most of the time, but not when the volume is turned down low on the Logitech unit, or when turned excessively high (much higher than I would ever want to listen to it at).. I get a loud buzzing sound. The buzzing is very loud at silent volume, completely gone near 1/3 of the way up, and back again when at 70% volume or so.. If I leave it near 1/3 volume or half volume on the speakers, and just control the volume through the Mac (as you would do, anyway) then its perfectly fine. However, I dont get this problem with the speakers plugged into my iPhone 3g. It operates perfectly. Any ideas whats causing this?

I'm running an extention lead from one side of the room to the other. I tried three with identical results. A 20 metre 10 yr old RCA lead, about a 3 metre new RCA lead, and a high quality 3.5mm to 3.5mm cable with a gender changer at the other end.

I cant actually set up the speakers directly by the Mac and plug it in directly, because I dont have enough power points or room near the desk. (arghh)

These are 5.1 speakers, so I tried unplugging the orange and black leads, as it says in the manual that green is suitable for stereo sound from a computer..

I dont get this problem with my high quality headphones, or my $3 computer speakers through the Mac. It's not a BIG problem, but I'm wondering if I should return these just in case theres a fault with the speakers. I'm leaning towards the Mac just being weird though.