I have read that some of the new Psvane 12ax-7 tubes could become microphonic after a while, but I haven't had any issues yet. My Psvane 12ax7 tubes are in my 1960 Pilot 402 receiver. They sounded pretty good right from the start but I noticed that after maybe 40 hours, they really opened up to flesh out the top and bottom end. Previous 12ax7 tubes I used were old NOS Siemens and Mullard. In my Pilot, the Psvane are superior in clarity, dynamics and frequency extension. I have never heard cymbals sound so natural. Keep in mind that this is my bedroom system. Speakers are refurbished Dynaco A-25, with Musicap on tweeter and VH Audio UPOCC copper Airlok wiring in crossover. This Airlok hook-up wire is really special...incredible clarity and dynamics.