Why do old tubes sound better than current tubes?

Tube are often represented as NOS that are probably old pulls, and often include testing results that turn out to be either false or based on poorly calibrated testers. Most tube testers do not subject the tubes to full power tests (the Amplitrex does do this) or give actual numbers for transconductance and other measurements, so it is hard to get meaningful readings in terms of how much life is left in the tubes.

I don't know to what extent older tubes decline without use, but, I have some old tubes that DO test very strong on my Amplitrex so I know that at least some tubes do not deteriorate with age.

As to whether NOS tubes are overpriced, that really is a value judgment. It is entirely up to each person to determine whether it is worth the cost to conduct the search for better tubes. In every instance where I, or my friends, have tried different tubes, we have found alternatives to what the manufacturer supplied that sounded better. That was the case with my amplifiers, and my amplifiers came from the manufacturer with old tubes (RCA bi-plate 2a3s, red-base 5692s). In my phonostage, I really like the result of using old Telefunken ECC803S tubes. I know that they are now unbelievably expensive; if anyone knows of alternatives that sound like that tube and cost less, please provide such information.

Manufacturers of tube gear almost always use current production tubes because availability and consistency are of prime importance. Since alternative voicing is really a matter of system matching and personal taste, it makes less sense to use much more expensive older tubes when the result (matching customer's needs) is entirely unpredictable. Thus, in almost every case, their is at least THE OPPORTUNITY to "improve" the result by selecting alternatives, whether other brands of new tubes or older tubes.

I think the very lable of 'NOS' is misleading.

Unless my parents or some other close relative bought some of these claimed "NOS" tubes when they were young and can now recall it vividly, and kept them in a box clean and dry for the past several decades.... well those tubes I'd call NOS. Otherwise, NOS means very litttle to me apart from that they are old... New? Maybe new to me... but NEW outright?

I'm going to be quite doubtful. But if my gear and my ears say they're a step up... I'm good with that, and that means only they measure out well according to orig specs... but certifiablly 100% virgin new? Probably not. not IMHO.

BLindjim,

Never thought about it but you are right. New old stock sounds like marketing jibberish. Its old, oh but its new! Oh sorry but I meant unused, not new. How do I know it was never used? Well, it reads like new. Yeah right! Funny.

I agree tube rolling can yield benefits, but the book is still open for me on the merit of NOS versus otherwise. I may never know though because so far for me, the fewer tubes, the better. And I like the few that I already have!

I claim to have golden ears in regard to NOS tubes. I bought some bargain NOS tubes that sounded half as good as full price tubes and I sent them back for full price tubes. MY point is, leave bargains for the bottom feeders.
I have bought tubes from "Brent Jesse" for years. A reputable dealer makes his living dealing with "golden ears", he can not afford not to deliver the goods. Since there is absolutely no way to tell an OK tube from the real deal by looking at it, and only if you got the ears can you tell by listining to it; your best option is to only deal with a reputable dealer.