Hi, I can't speak to the cause but if you run balanced cables you probably won't get the buzz. Although you might need a different soundcard to do that. I drive my TR-8s out of an afforable Emu 1212m and they sound very respectable.

The only other thing I can think of is that you might have your trim pots cranked. Try setting them to 12 o'clock and see if that helps. :)

I keep the trim pots at about 1 o' clock.

I was suspecting it could be the unbalanced cables. I am thinking of buying a Focusrite Saffire but that'll probably be until after the new year.

Anyone else know what could be going on?

Don't get me wrong, you can run the TR8s with unbalanced cables without hiss. This is something to do with the audio bus in your soundcard/compie. FWIW down the road, the saffire will definitely fix that.

That stinks cause I thought Apple's internal soundcards were supposed to be top tier. Maybe it's a Powerbook thing. I wonder if this would happen on a desktop system.

Depends. The native PCI bus on some motherboards can be dirty but often they are OK-ish. It definitely won't happen if the desktop has basic decent soundcard. 8-)

I'm anti-Apple so I can't say one way or another what the deal is there. Could be something simple, try another cable first.