Fatparrot has a valid point.
And EVERY NOS/NIB and even old "used but test good" tube I have ever tried has sounded better, period. That's IMO, and in my system. Now I have not tried them all, but who has? But I have tried Sovteks, Svetlana's and Reflektor. Forget Chinese, too many other options. The only reason I have Reflektor's in my system now is because my pre was designed for a specific tube, and Russian is the only choice.
And the NOS ones sound MUCH better.
Yioryos, you state,
"Technology gets better and I don't accept the theory that we no longer can produce equal or better tubes".
If most cases, that is true. However, tubes are essentially obsolete except for specialized applications (radio frequencies & graphite plate tubes used in industrial heating.) In addition, even during the heyday of tubes, matching and testing of tubes for audiophile purposes was unknown.
And EVERY NOS/NIB and even old "used but test good" tube I have ever tried has sounded better, period. That's IMO, and in my system. Now I have not tried them all, but who has? But I have tried Sovteks, Svetlana's and Reflektor. Forget Chinese, too many other options. The only reason I have Reflektor's in my system now is because my pre was designed for a specific tube, and Russian is the only choice.
And the NOS ones sound MUCH better.