The problem with NOS 6SN7 tubes these days is the fact the desirable brands like the Tungsol Round Plates, Sylvania GTs, Raytheons, Ken Rads, RCA red base are becoming scarce. What you see on eBay is a crap shoot. Most of these tubes are not being measured thoroughly and will most likely be unacceptably microphonic. There are a few trustworthy tube dealers out there that have a nice stash but you will pay for them. FWIW I have heard from Ralph based on feedback he has received from customers that the new production Psvane 6SN7 is quite good. I intend to try a set in my custom MP-3 when I receive it.
