National Vacuum Tube Golden Series For 12AX7HiFi. I suppose you could call it a vintage vacuum tube. I purchased it from a vacuum tube specialty store that repairs phonographs. I bought it about 10 years ago as a replacement for amplifiers and effectors that use vacuum tubes. I used it a few times as a replacement, but I didn't use it permanently for years. After that, due to the rapid advancement of digital technology, I had no opportunity to use it and have been storing it.