Well I am happy to have finally sorted through enough N7s to have all of the TS RPs in one tray which has a bunch of other fairly good to superb ,no not the TS level tubes.The bad news or good news depending how you see it is that this is not even close to all of them.I have atray of RCAs the good the medium and the not so great IMHO. One tube a l only single is just called a CCA not related at all to 6922. It is definately an RCA with a CRC marking.
I have had the experience of dead silent tubes become microphonic it is in the non reinforced architechture. Curiously I never hear the whine or ringing people describe. I do have a resolving analytic system which will show warts and all.
The dealer cannot promise that even the most rigid will stay non micrphonic. What they do is better matching for gain etc and intertriode imbalance. These are like any twin triode one can be more than 10% different than the other. This does have a measurable effect but again you have to be looking for it. I know because I have had pairs that weren't close and used a SPL meter to measure the difference it is there, but not obvious.
