Why are NOS tubes considered superior?

The older tubes are better IF you have a reputable supplier that properly tests them. Some of the tubes are less microphonic, some just sound better because of the midrange bloom. This is a fine example of tweeks, but I have done this to my ARC gear with GREAT results. If you would like to know my tweeks, write me off line.

Some NOS are better, some are not. Know what you are buying. Many current manufactured tubes are the best ever. Sometimes mid-range bloom can be achieved with NOS tubes because of inherent problems with equipment and equipment matching. Just because a tube is NOS puts it far from a recommendation. Good luck.

NOS tubes are highly sought after by guitar players for our vacuum tube amps. We use a lot of tubes. There are web sites that specialize in NOS tubes. Mullards,Telefunkens, Brimars, RCA's and GE's sound dramaticaly superior to new Soviet and Chinese tubes. The Russian tubes have been improving and are "good enough" for most uses. The Chinese are mixed; many are microphonic and fail after several months. It has to do with the mechanical assembly and the rare earths used in the tubes. The factory skill set that was lost when the West shut down the production lines has not been recreated. Perhaps it never will be. For now there are good stocks of JAN (military)and old TV/Radio shop stocks to be worked out.