There could be charge pumps inside that bump the voltage being sent to the tube to the 220 volts, but I doubt it. In the guitar world, there are quite a few tube pedals that run preamp tubes at around 12 volts, but very few still in production that exert the full voltage available to the tubes. From what I can tell, you won't be able to output 240v from USB and will need a kettle lead and a full-sized transformer. I really can't imagine the Aune T1 has any of these in the way that full-sized amplifiers have that cost ten times the price do.
I thought that I understood the role of the tube in Aune T1, but now I am not so sure.
It was said that the gain achieved by the tube is 1, that the tube is used as "buffer". If I am not mistaken, a tube used as "buffer" and with gain 1, then serves the purpose of "distortion" (or "modulation") phase, it is there only to introduce those distortions pleasant for human ear found in preamps/amps built on tube technology. Which is, BTW, great, I want sound that is pleasant for my ears, the measurements and instruments be damned.
But now the quoted chapter indicates that higher voltages can be provided by voltage pumps and that sounds like an amplification stage to me...
Which is it, please? I am considering pairing HD600's with either T1 or O2/amp and am a bit suspicious about the consistency of T1s.