Lately the sound of my system has been slightly noisy and less dynamic, something missing. First thing I noticed was that one of my Tung Sol KT120 tubes on my Rogue Audio CMII is dead! Won't bias- zero. Received the new set and things are sounding much better. Decided to swap in my never used new production Tung Sol 12AX7 just for kicks and wow, the detail, treble extension and bass is much better than the somewhat new NOS Amperex 12AX7s that I paid a huge premium for. The Amperex sounded great at first but rounded off in a hurry. Then I noticed that my prized 12AU7 Amperex Holland Treble Clef logo from the 50's is microphonic and noisy like a mofo! I paid a small fortune for that one! Swapped in the stock $10 JJ and the sound is much more pleasing- clean, extended, dynamic but a little dark. Since I like the Tung Sol sound so much I ordered some new issue 12AU7s to replace the JJs. Through the whole exercise my amp is telling me that NOS tubes are not worth it any more- for sound or longevity. Very surprised by this.