I've purchased the majority of my NOS tubes on eBay, or from eBay contacts over the last 5 years. All the purchases(probably 40+) were excellent, but for one(if you e-mail me, I'll let you know his user name). I got four counterfeit Telefunkens from him. Anyway- The majority of tube sellers on the 'Bay are upright and knowledgable(especially the German ones). You just have to know the right questions to ask to find them. Don't buy anything from those sellers in Asia. they are expert counterfeiters. If you visit here, you'll find a comparison chart that indicates what kind of sound to expect from various 12AX7s: (https://www.tubeworld.com/12ax7.htm) The flavor of the 12AT7s manufactured by the same companys will be similar. If you like transparency, lack of colorations/microphonics, no phoney mid-range warmth: try the Siemens and Telefunkens(from the 60's).
