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

Hi all ! A tube guy once told me the reason the older tubes sound better than the new tubes is back in the day they could use " nasty chemicals " . Apparently those chemicals make a better tube . Dont really know if this is true or not .

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.

The tube manufacturers of today have lost the "old formulas" for making quality tubes. The Russian tubes of today were formulated on "Military" tubes designed to keep Migs flying through "atomic clouds"!

There was a link on the new Mullard site worth checking out. It showed the process of making tubes in the 50/60's. Watch that and you will understand why a) they don't make them like they used to and b) why there was a big push to go to transistors. The amount of machinery, the precision necessary at every step, and the error/failure rate even at the Mullard factory are fasinating. That said, some of the new manufactured tubes are pretty good and seem to be getting better.

It would seem by trial & error over the years that there should be no problem manufacturing a superior tube. Even the machinery involved in producing tubes could be compacted, streamlined, and improved given this computer age. It may simply come down to supply & demand, maybe not enough orders to justify the factory investment. Audiophiles represent a small segment of society, thus the demand is not that significant since a tube's primary application is an audio circuit.