USB and BNC cables I am using with the Bel Canto link are not the equal of my Nordost Valhalla AES/EBU digital cable; (d) the fact that I use my Powerbook for writing, scanning, email, and other functions rather than exclusively for music playback has introduced various factors into the interface that compromise sound quality; and/or (e) the Bel Canto link is a less than ideal interface.