While I realize this thread is old, I can tell you from experience that the folks at Sophia are very accomodating and quite reasonable with repairs. I have one of their integrated amps, a 300B single ended unit that uses a 206 output tube. It has held up very well over the years and is honestly one of the best sounding amps I have ever heard. I would agree that they are probably reticent to publish their schematic due to piracy concerns.
