Mini to Toslink adapter for Airport Express...

For $100, you can get a VanDenHul Optocoupler toslink cable with a mini-plug on one end and a normal optical plug on the other. That way you don't need an adapter. And the cable is supposed to be one of the best regardless of price.

I ordered mine from Divergent technology (or audio) in Ontario, Canada. They distribute VDH products.

I'm quite happy with it. Read this:

http://www.6moons.com/audioreviews/toslink/toslink_2.html

or....on the other end of the spectrum.

soundprofessionals.com

The sell Toaslink/mini cables as well as the adaptors. They are reasonably priced.

I guess it is all about how serious you want to be about it.

Buy a mini to Toslink cable. They range from cheap to fairly expensive. Some can hear the difference and some can't. Buy a cheap one and see what you think before laying down more scratch.