I second the VDH Optocoupler.
Review (supposedly the WireWorld Super Nova is good too):
http://www.6moons.com/audioreviews/toslink/toslink_2.html
http://www.vandenhul.com/p_B42.aspx
Review (supposedly the WireWorld Super Nova is good too):
http://www.6moons.com/audioreviews/toslink/toslink_2.html
http://www.vandenhul.com/p_B42.aspx