Why Can't Tubes Be Mass-Produced Cheaply?


I often read that old tubes manufactured from the 60's or earlier are collectible items and often much sought after, and new tubes are not as valuable. Reasons cited are that these older tubes are a rare species, and they often sound 'better' and hence the hefty price tag on them. I am puzzled as to how these older tubes are different from the new ones and why they are better-sounding. Why can't technology today produce tubes that are similiar in quality to those in the yesteryears, or even better them? After all vacuum tubes, electron tubes or valve tube(where they call it in Britain) are electronic components made up by plates and filament. What happens if these old tubes become extinct? Why are there still so many of these old tubes available for sale although it has been almost 4 decades since they were manufactured? I mean once these tubes have run out of life they will basically be disposed off.

Pardon my ignorance as I cannot seem to find any discussion on this matter elsewhere. Any opinions would be much appreciated.
ryder
I just worked with one dealer who will not sell anything other than new Electro Harmonix tubes for use in a few preamps that are "demanding" of 6922 tubes placed in critical positions where low noise and reliability are important, along with at least a touch of musicality. Of course I will also be trying a pair of Amperex PQ white labels I have around here.
Stevecham,

What I said in my post is:

When comparing small signal tubes such as 12AX7, 12AT7 and (especially) 6922, the modern versions from Sovtek and others are nowhere close if the comparison is made in a critical position.

By critical position, I'm referring to small signal tubes in EAR 834, Aesthetix Io and Callisto, Audio Research Ref 2, input circuit (12AT7) of VTL 450, 750 and 1250 to name but a few.

If you doubt me, do an experiment by putting new production tubes in the first stage of an Aesthetix Io and to make things fun, go with a .2 MV cartridge such as a Koetsu Jade.

If you can get new production tube to work as well as Telefunken, you need to reveal your magical source. I have a lot of people, including several manufacturers that would like to buy some of these tubes.
Some of the difference in opinion on whether NOS sound better than current production can be differences in hearing. As I get older I am less and less able to tolerate harshness or grain or glare. Speakers and gear that I once enjoyed now grate on my ears.

So my guess is that people who think that current production tubes sound great are better able to tolerate whatever distortion it is that hurts my ears. And that's not a bad thing, it saves you a lot of money, but your opinion may change over time.
Albert's point is well taken and something I mentioned earlier. If the circuit is demanding, like driving real hard or whatever, then there probably are tubes that work better than other. Maybe NOS, maybe not. I have also had good results with new JJ and EH small signal tubes. (I have a pair of the new ECC99 on the way, heard several good reports on these.) I'm using some NOS Tesla right now that I find very special and they only cost $40 a pair. No, I won't tell you which they are cuz I don't want the price to jump. ;-) In my amp I have found that the new production EH EL34s are better than some very high dollar NOS EL34s that came with the amp when I bought it. These were supposedly the best EL 34s ever made. I can't remember exactly what they are and I'm not at home right now to check.

Not to stray off topic too much but I have moved away from such equipment because I have found other designs that work better without the need to drive the tubes hard. I've also not found in my humble experiences a design using the 6922 that I like. And I've tried the PQ white labels and a few others. I'm not slamming any make or model, just hoping to help explain why some may find NOS necessary and others can find great performance with some current production tubes.
BTW, to those who sent me email. Hope you don't mind if I answer here so I don't have to reply more than once. Long story short, this thread contains the sum of my experiences. Maybe not in any detail, but the high points are here and not just in my replies.