iTunes sound quality

I'm about to take a hammer to my MacBook and its probably all my fault anyway. I recently bought some Logitech G51 Speakers and they work wonders with my ipod and a RCA analog cable. When I connect my Macbook, once again analogue, it sounds terrible: There is a deep hissing noise. It doesn't happen with cds played through VLC or movies also played through DLC. Video and Audio streaming from the net is also good. The sound is so bad with Itunes, that there are times when I actually can't hear the words. I use the same cables everytime to connect to the speakers. It also sounds awful when I just use my standard on board speakers.
I read on a different forum that it could be a problem with Quicktime, but I can't seem to change any of the settings that they recommend which I assume is due to the difference between XP and Tiger.
I'm on my last legs with Itunes, so any help would greatly appreciated.

Maybe you've considered this already, but the first thing that came to mind is the iTunes EQ might be engaged with some weird setting.
If that doesn't apply, is there a chance you have encoded you music with a low bit rate?

wilkie0408 said:

..... I connect my Macbook, once again analogue, it sounds terrible: There is a deep hissing noise. It doesn't happen with cds played through VLC or movies also played through DLC.

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