I've listened to audio from my MacBook using headphones and the quality is excellent so I thought I'd try the optical output and connect it up to my Yamaha amp using a standard optical cable connected to a standard mini-toslink adapter in the MacBook. Listening to the sound output quite carefully I noticed it wasn't quite right -- the sound had what my friend described as "graininess" to it, which could relate to the word clock, synchronization or something like that. It sounded as if brief, intermittent parts of the music being played were being taken out. Basically, it didn't sound good.

Yeah, so, I'm not sure what the solution to this is. Does anyone have any ideas?

Many thanks.