The USB standard is 15 feet. The big reason for this is that the cable also carries 5v which is how some many USB devices get their power. Power drops over distance.
You can extend the USB with various devices but I personally use an Opticis. Color me lucky but I find it to be a good value and reasonably priced. Also, there is a big advantage to isolating the computer and the DAC from each other. A fiber cable (be it Opticis or for that matter Toslink) does that. Instant way to avoid any ground loops and possible hash.
I am a big Squeezebox fan - beyond the CAT5 you can order it with WiFi capability and if you are lucky (environment dependent) you can eliminate cabling entirely.
>Fatparrot I don't know, you are most likely right. However there have been glass versions for a few years now. Check the famous shoot out in 6 moons when a glass Toslink equalled the best SPDIF cables.
