Why do old tubes sound better than current tubes?

I think the tide is turning a little. The Genelex/Gold Lion reissues (Russian), for instance, are gaining real respect. I've personally replaced "Holy Grail" Mullard xf1 EL34s with Genelex KT77s because the new tubes sound quite a bit better in my amps. And the Sovtec 12AX7LPS is a winner. The reputation of many of the old tubes is, IMHO, a combination of performance and mystique/nostalgia. We're paying a lot for the latter.

I also believe the tide has turned in favor of the new tubes. You can get on the boards and read all you want about the "Holy Grail" tubes of yesteryear but I gotta tell ya, many of the new tubes are simply fantastic. I'll be reporting on this subject in TAS and on the AVGuide site. Frankly, it's great news and we all win.

Peter Breuninger
Sr. Writer, The Absolute Sound

The secret is inside. Quality of wire, cathodes, plates, durability...
Low noise (ask Aesthetix Callisto owners, they can tell you something about that), low microphonics, maybe shock resistance and so on.
forget the pricing for NOS, turn back the time 50 years and try to imagine you have in your left hand a Telefunken, Made in Germany and in your other other hand you have a modern Sovtec, Made in Russia, China or in other dark countries.
Do you really think they are equal? :-)
I know the answer. :-)

But we can't make money with old tubes, so let's be happy what is available today. It isn't that bad.
But not equal. I tried some modern tubes, great for the money, no doubt, but fantastic?
Fantastic is something different. But it depends on the quality of the System to hear these differences. I hate the NOS prices, I also bought a set of modern ones too with them to compare. I got my result.

The best answer I have ever heard is that some of the coatings used in the olden days are too environmentally unfriendly to be used in modern production. Another thing that you cant discount is the knowledge gained by experience of the toobe makers of old; trade secrets, lost in the sands of time :) Also, people were forced to use their BRAINS in those days.

I am happy to hear that at least some new production tubes are getting rave reviews but I remain skeptical about preamp tubes. I have seen so called preamp tube shootouts where the reviewer tested one tube of each type and drew concrete conclusions from such a limited sample. Anybody who has ever built gear or rolled a lot of tubes knows that two good preamp tubes from the same production code can sound vastly different - not to mention sonic differences due to minor changes in plate and heater voltages.

Mike