Why aren't new vacuum tubes as good as old ones?

I have always thought it was quality control. I know that Chinese tubes are sorted by quality and sold at different prices. I suspect that many tubes in an earlier era were merely discarded. I remember radio stations buying tubes in big boxes and plugging them in side by side. Those that didn't glow were quickly discarded.

I also expect that the women who made them became quite skilled and consistent. I doubt if that level of skill is available today.

One thing is for certain the old NOS tubes of even the 1970s are become rare as hen's teeth.

I think you guys are under estimating the importance to WE of reliable tubes and the fact that there was competition among manufacturers.

Jwm, I sort of agree although there are great sonic differences among the NOS also. I think either the skill of those who were making the NOS or the QC then with many tubes discarded.