Why do old tubes sound better?
They have more experience. ;-)
I think its simpler still. Especially if you think about the times the vintage tubes were made.
Demand. Materials. QA.
Back in the 40s, 50s, & even in the 60s, times were different. The thinking was more geared towards making a better product than a cheaper one more often than not. Materials too werent in short supply usually, nor were these materials skimped upon employing mere percentages of this or that instead of using 100% of them. Quality control too was on a higher level as well I would think. During those times, sales were generated by producing better and not quite so much as making the faster and cheaper products, though the latter always will be a facet of business.
Probably as important too, the apathy level on the job was lower than it is in the workplace these days and may well have played a significant part in the whole of things.
True too, those original tube magicians that were around then arent around now, nor is the content of their heritage. Doubtless few magicians apprentices were getting on board in the business as silicon was becoming all the rage in the late fifties and sixties when the transistor came into being. So I suppose it came down to a main precept of business, demand.
You gotta know too, tube makers were almost like VHS machine & tape makers lots of brand names but scant few actual makers. RCA was a giant in the tube industry, and their plans changed in house as well in which direction they would be going forward with.
That old adage They dont build them like they used to! still has merit and reasons why.
There are some pretty decent tubes being made today though. Even in Russia. I have some and enjoy them a lot. CED Winged C EL34. Im thinking about trying some of the KT 77s too as mentioned above maybe.
In the 9 pin arena matsushita Elec. Made some back in the 70s that I feel are on par with some of the far earlier Amperex 7308 & 6922s. I had some of them a while back.
On the flip side, I tried some of the Tung Sol 5881 re-issues and sent them back quickly.
As for the lable NOS . I feel that too is more myth than fact. 50, 60, & as much as 70 year old tubes no one ever used? Really. How do you know? You had them in the closet for all of that time? Sure.
With tubes though, its as much about the vendor as it is about the tube itself. Theres one or two vendors I simply WILL NOT buy from again. Period. There are others of course that Ill accept whatever they sell me as golden, and trust implicitly.
or it could just be things change.
Perhaps tube topology designers ought to alter the other ingredients in their designs so as to attempt to recapture nostalgia by utilizing these newer tubes instead of emulating the SS like sound so commonly found in todays tube amps. After all, tubes are tubes and should IMHO have a distinct voice well apart from that of chips and silicone.