NOS tubes

My question is this, why are NOS tubes percieved/ or not, said to sound better than newly manufactured ones, with all the new technology and manufacturing techniques and materials you would think the opposite to be true, but then again I guess it’s the same as solid state vs. tubes,
My perception of this is that NOS tubes were manufactured in the hey day of tube use in TVs, Radios, military equipment, etc. etc.  Because they were so essential to, in many cases, sensitive circuits, those tubes were manufactured to very strict, exacting standards leading to the coveted sound of many NOS tubes.  Interestingly, it seems that specific NOS brands have a universally recognized sonic signature.  To whit RCA clear tops are, well, clear and dynamic whereas Mullards are often considered as warmer and more forgiving in sound quality

I am not in any way an expert regarding tube history so I welcome others to correct me if my understanding is in error.

I use new production Gold Lion tubes sourced from Ron Sheldon's Cryoset store.  In my Modwright Signature mod. SACD player I use NOS Tung Sols as Gold Lion does not make 5687s.
My understanding was pretty much EVERY re-issue tube made today is made on the exact same manufacturing equipment they used back in the day.I don’t mean similar I mean complete refurbisment of the old gear.Even with advancements in metal purity I can’t see the NOS and reissues actually sounding any different..
@freediver  No argument from me about what you said above. If what you say is true, why all the fuss about buying NOS tubes rather than current production?  Because NOS adherents will use numerous adjectives to describe the sound of their gear with a particular NOS tube vs. another NOS tube, while bemoaning new production, I assume that they at least see something unique in their production and that it is not just a nostalgia movement for things from the 50's and 60's.
Not all NOS tubes sound better than current production. Some do.
You'd figure that with social media and instant feedback today, that some tube maker would realize that making a superior product would kill the competition. That's assuming anyone gives a crap anymore.
I got a set of electro harmonix 7591 output tubes and 2 of the 4 went kaplooie in 2 months. I then sourced 4 nos Westinghouse and couldn’t believe how much better they were in their power delivery and Sonics. I only use telefunkens or Mullards for tone and phono stages. 
They sure were doing something differently back then if the equipment today is the same. 
Back during the golden years of tubed based electronics EVERYONE in the electronics industry and military was using this technology, do you think the tubes themselves were important? They were! And not all companies were equal. So yes and no is the answer to the OP's question. As is the case today there are some tubes being made that are STELLAR but most are pedestrian at best.

Matt M
I don’t think that’s true freediver. Current production tubes are made in Russia and China and their construction is very different from the classic tubes made in the US, the UK, Holland, West Germany and many other countries. I’m not saying that they don’t make good tubes today, but they’re not made on the same equipment that the classics were.

There are cases of countries buying tube manufacturing equipment and using it after the original companies shut down in the 1970s. Ei in Yugoslavia bought Telefunken’s old equipment and someone in Japan ( Mitsui maybe?) bought some of Mullard’s old equipment and continued making tubes.

Some people prefer current production, I prefer the classics for the reason hifiman5 stated. Different brands have their own sound characteristics which can be used, along with other accessories, like cables, to tune the sound of your system. It’s just my preference. Some people don’t like to use tubes at all. They prefer SS.
To answer the OP's question.  And I'm talking about preamp tubes not power tubes.  Tube quality was very important back before transistors replaced tubes,  when tubes were used in essential functions in airplanes, radar, early computers, television broadcasting, medical equipment, etc.

They are getting better at making tubes but the really good ones often cost as much as NOS.  You would think that eventually they will make tubes that sound better than NOS with the technology available today, and I think they probably will, but for now I prefer old stock to the new production tubes I've had in my system.
Tim deParavicini (EAR-Yoshino) told me old tubes are better because the people making them did so as a career, with a lot of experience under their belts before they were promoted to the position of making them. To the people making them today, doing so is just a job for now---they are not experts in the field, as were the old-timers. He told me he prefers old Mullards, which may be partly because he is British.
Vacuum Tube Valley had a report on this. Look it up! It seems that the cathode-coating chemicals were of a much purer quality. Vacuum pumping went on longer, resulting in a better vacuum. Grid wire spacing was held to tighter tolerances.      Speaking from my experience as a longtime tube user I prefer using vintage used tubes that still test GOOD over present day production!
bdp24 and robererman and tomcy6 nailed it. 
Thank you gentleman for your responses, my question was posed for two reasons1- my own curiosity and 2- a few months ago I bought my first tube amp , and you know what happens after that!- correct, tube rolling questions!!
The new Sophia/Full Music 67SN tubes that are made in China are (IMHO) superior to the many NOS tubes that I have tried in my Atma-Sphere Amps.

These tubes present a wider frequency response and a deeper soundstage.
Although, they are quite pricey at $100 each for a class A rated tube.

So, high quality tubes can be manufactured to perform as good or better than the earlier counterparts. 
But, the market for them is small and I don't see that changing.

What amp did you buy wow?  If you decide to start rolling tubes, it would be best to work with a good tube dealer (Brent Jessee, Andy Bouwman at Vintage Tube Services or Kevin Deal among others) rather than try your luck on ebay.  They can offer educated opinions on which tubes might work for you and you can trust that you are getting what you paid for.  It will save you money in the long run.
I've never enjoyed my conversations with Kevin Deal.

I always enjoy talking to Mr. Deal. Very informed and reasonable man. He is, in his arena, an artist and artists are sometimes misunderstood.
@tomcy6 I got a rogue audio Cronus magnum II, loving it so far, just now getting broken in
Yep, not a fan of Kevin Deal on the phone or in person.
Mr. Deal must be a somewhat polarizing figure.  Not that long ago a thread was very active about bad service from Mr. Deal.
That's a nice amp wownflutter, but I can't tell you who would be the best tube dealer for you.  When you get ready to try rolling I'm sure there will be people here who will be happy to offer advice.  Enjoy!
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One thing is certain. Most mass produced items today are made a cheaply as possible, and many times quality is allowed to suffer for the sake of profit.  There was a time in the U.S. and other nations when cost was factored in but also balanced with quality being the driving force. 
Does this apply to all old production tubes?  Probably not, but it surely applied to many of them, and the results speak for themselves.  I collect, use and sell a lot of vintage gear from tubes to guitars to amplifiers.   I use NOS tubes in my Engl Fireball 100, Mesa Rocket 4Forty and my brownface Fender 6G3. 

When I was younger I tried all the modern 12AX7 12AT7, EL84, 6L6GC, and EL34 types.   JJ, Sovtek, EH and Ruby always performed pretty solidly.  Mullard and Tungsol performed terribly.   Even the Chinese high gain Shuguang tubes were better IMO.  But I have had the best experience with the various NOS units I've had the pleasure of owning, and after 11 years of research and forum hopping as well as experimenting, I've happily persuaded others to give old production a chance.  Most people are very happy with the results.   I use a custom DIY curve tracing kit in combination with a Hickok 600A serviced and calibrated by Radiola Guy, who sadly no longer performs those services. 
I can tell you that Brent Jesse is one of the greatest guys to talk to and work with.  Anyone who values his opinions and knowledge is ok in my book.   If I don't have what someone is looking for or think he could help them in any way I can't, I would refer him in a heartbeat. 

One thing is certain. Most mass produced items today are made a cheaply as possible..."

That is not certain at all it sounds like you shop only at your American WalMart store.
Don't forget: The Military used to use tubes in its field equipment. You don't use cheap stuff in this application. The 6H30 DR "super tubes", touted by Balanced Audio Technology, were made for Russian fighter jets.

I think everyone who uses tubes should send a note to Western Electric, who is currently building a production facility in Georgia, and express their desire for their favorite tubes (I've already done this). Who knows, maybe they will build tubes, other than just 300Bs, with super-high quality.
Nobody can match the construction quality of the 1950  tubes e.g. Amperex.Todays tubes don't come close.Jump on nos Amperex from 1950s.
Don’t forget: The Military used to use tubes in its field equipment. You don’t use cheap stuff in this application. The 6H30 DR "super tubes", touted by Balanced Audio Technology, were made for Russian fighter jets.

>>>>The US used tubes in its commercial and military aircraft radios, too. But tubes went the way of the dinosaur a long time ago in the 80s. Now pilots and air traffic controllers have to suffer the sterile sound quality of solid state radios. That’s progress for ya! Tubes were resistant to nuclear bomb EMP but that threat went away 35 years ago. Or did it? 😳
in the 70s I had a direct line to military 12AX7WAs and other goodies through by bud in maintenance at Goddard Space Flight Center. Sweet! I also had a line on regulated power supplies taken from dismantled US Navy communications centers.

That's a little harsh IMO.  Coming at me with insults, especially
when what I said is 100% correct.  The entire purpose of mass production is to cut costs, and today most of what is mass produced by the millions suffers greatly in quality as a result.  Modern manufacturers mostly operate on a much difference set of standards of acceptable quality presented to consumers.  We no longer have tubes being mass produced for military or laboratory equipment especially, so it is very safe to say that what is available to us today can not possibly meet those standards.  As I said before, there are exceptions to everything.  
@clearthink  - Wow, in seeing your other posts I don't feel so bad. You are just a very nasty person to everyone.   Have a nice day my friend!
The entire purpose of mass production is to cut costs, and today most of what is mass produced by the millions suffers greatly in quality as a result.
That's actually a misnomer. The primary purpose of mass production is to reduce overhead as a share of a product's total cost of production.

Mass production can offer other benefits too, including interchangeable parts, just-in-time inventory and - believe it or not - quality control. Consider that next time you use your cell phone, or drive a modern car.
That is one side of the coin.  But you can't discount the other side as hogwash. 
Imo, like a lot of things back in the day, NOS tubes were made to a standard, not to a price as they seem to be these days