well i purchased a powermac g5 dual 2.7 a few weeks ago and its a great machine. I recently ran into this problem though. I have a set of z-5500 speakers and i had them hooked up to the powermacs rear and front inputs via stereo plug connections, and its been working out pretty well. Suddenly though im getting this huge hissing noise through my z-5500s. I checked the wires and if its my z-5500 causing hiss. The only thing left is the powermac g5. Im wondering what the hell should i do!!!