The preamp clearly sounds best - significantly best - with 6 or 7 volt tubes, but I have tried NOS and new production tubes and always have noise problems. I have tried perhaps half dozen different tubes, but always the same: NOISE. I particularly like 7DJ8/PCC88 and have tried several pairs of them. It is nice and quiet with 12V tubes, but the sound is degraded. Currently 12AU7WA/6189 French Mil.
PS Audio says that if it works properly with the stock 12V tubes that is the end of their responsibility.
Does anyone know of a 12V tube that works well in the preamp that approaches the sound quality of a decent 6 or 7V tube? This is my last gasp with this thing before I replace it. Otherwise I think this is a very thoughtful design of excellent quality.
Thanks in advance.