I have a tube-based system (linestage, phono, and amps are tube-based), but I am not inclined toward tube digital gear. What part of a digital source is really provided by the tube? Often the tube is just an output buffer or one stage of unneeded amplification. While a tube can be inserted into what is inherently a solid state chain, that generally means trying to artificially create a "tube" sound.
Vacuum State, makes mostly tube gear, as their name implies, but their modifications do not involve adding tubes. I've heard their modification to the Sony SCD-1 machine and the sound is terrific. I like the sound from my non-tube based cd player too (Naim CD555).
The one line of tube-based digital gear that I think sounds really good are the Audionote DACs. But, these can be terribly expensive. I've heard the Ayon in a system with Ayon amplification and the system sounded pretty good, but, I haven't heard that player in my own system or in any sort of side-by-side comparison.
