It uses subminiature tubes which have no provision for socket-mounting, but supposedly have a very long lifespan (around 20,000 hours if I remember right). I've never heard of anyone trying to swap them out.
Audio Aero Capitole-Changing Tubes
I have been reading about the Capitole and while it sounds like it would be incredible to own, I have learned that the tubes are hard wired to the board so that changing them requires soldering a new set on (supposedly). Is that true? What is one supposed to do when the tubes need changing? I would never attempt this myself. Would appreciate hearing from Capitole owners as to what you did. Thanks.