Learning is defined by educators as a change in behavior as the result of experience. 8)
Welcome to the VOS/NOS thang. Happy hunting. Keep on keeping on adding to your inventory and variety! Some tubes work well in some amps better than others. In rare instances a new production tube will sound better in a particular application, but frankly your experience with your amp is often the norm when comparing sound of VOS/NOS to modern production or so called reissues... The choice of guitar used can also influence what preamp tubes sound best to your ears. With a suitable cool-ection of various VOS tubes it is really fun to voice an amp to a particular fave guitar if desired. :wink:
There is an obscure tube weenie magazine called Vacuum Tube Valley, in one of the issues there is an article about an extensive 12ax7 shootout. Charlie Kittleson, the editor, is an electric guitar player as well as knowing tons about hifi. Copies are not cheap for back issues, more than 12 bucks apiece and worh every penny, and they are available still. Obtaining a copy of that article is one of the most helpful bits of literature for learning about the idiosyncracies of NOS 12ax7 tubes, and there are plenty! Have to thank and give kudos to sixveesix for turning me on to that article when we were neighbors a few years ago. Armed with that info, I began a 12ax7 purchasing odyssey on ebay that was very helpful to my ears and amps. Speaking of German 12ax7's, I saw a quad on ebay of Siemens VOS shortplates with Mesa Silkscreening a week or two ago, and those Siemens are some of the nicest made and sounding 12ax7's ever.
+1 for the Sylvania blackplate el84's, Jan Philips el84 blackplates are basically the same tube.
