Hi Rafael,
Thanks for the kind words. While I have always been a lover of tubes, I would say that one of the worst places to have them is in a DAC. A properly done solid state analog output stage can sound much better than a tube DAC. There is too much distortion and noise produced by tubes. Really I would not even focus on tubes versus solid state here. There are much more critical things going on like the conversion itself.
Currently USB is not ideal nor is it that important for use with a music server. Our unit accepts anything up to 24/192 through either AES or SPDIF. We have many customers that are very satisfied using USB to SPDIF converters in order to achieve 192kHz if they cannot use AES or SPDIF sound cards.
Right now we are extremely back ordered and focusing on filling orders. When there is something to announce, I will let you know.
Best Regards,
Jonathan Tinn
Playback Designs