I don't have to know what I'm missing out on!
Actually, you might want to know, because not all NOS is prohibitively expensive. Please read on.
New production Mullard tubes are assembled by hand in the Reflektor factory in Saratov, Russia and their excellent performance closely mirror's that of vintage Blackburn construction."
Unfortunately, that’s more marketing-speak than truth. Boogie’s right about this.
The new reproductions are superficially similar, but inside the tubes the internal parts quality and tolerances are not the same, and even how the plates, getters, and other subassemblies are put together isn’t the same. I’ve seen enlarged photos showing the differences, and it’s interesting to see how many corners are being cut in tube manufacture today.
Back in the day, folks had to depend on tubes for more than guitar amplifiers and retro audio gear. There was medical equipment, aircraft controls, military communications - hell, even car radios were tube. Everything electronic depended on tubes.
In other words, the product was infinitely more essential, and had to be rugged and reliable.
Tube manufacturing was a big, cutting-edge industry back in the day, and specialists with lots of technical experience making the best they could were in it. Today’s equivalent would be the semiconductor industry. Those generations of experienced tube technicians and engineers are no longer active.
The differences in manufacture also extend to the machines; the machinery used in Eastern Europe and the Far East was mainly bought from the West when the West stopped making tubes, by 1979 or so. Most machines were already pretty old at that point. The machine tools were also old.
Add all these factors up, and it’s little wonder that new and NOS tubes behave differently electronically and sound different.
I first became interested in NOS tubes around 15 years ago, when my first Two-Rock came with them. I had several conversations about them with the amp’s designers, and started trying NOS in other amps. Turned out it was indeed a pretty big deal.
Because these days preamp gain is more of a thing than output tube gain, the preamp tubes are the place to begin experimenting. Few players are driving output tubes very hard any more.
All three of my amps have NOS preamp tubes, and two have NOS output tubes. The output tubes in the third amp will be replaced in a few months with NOS. My experience is that the output tubes matter, but start with preamp tubes.
NOS tubes make a very good amp better, and a great amp that much more satisfying to play. Of course, this presupposes that the player groks the difference between very good and excellent tone. Some do, but most haven’t the listening experience at first. But take the NOS away after getting used to having them in an amp, and they’re missed, as in, “Where’d the tone go?”
My feeling is that while subtle at times, the biggest difference using NOS is being satisfied with my tone, long-term; by that I mean spending
years with an amp and not feeling vaguely dissatisfied. Not casting about for some new ear candy all the time as I once did. Most of us have had that experience, that their amp for whatever reason isn’t cutting it any more, and surely there must be something cooler and more toneful to shop for! But at this point, if I buy a new amp it’s to add different types of sounds, not to find something that sounds better at the types of sounds my amps make.
In terms of dollars invested, even the rarest, and/or best sounding tubes are much, much cheaper investments in the long run than buying and selling amps in search of ever-elusive audio satisfaction. As for reliability, in 15 years I’ve had exactly one NOS preamp tube go microphonic, and one NOS output tube get a little noisy. The preamp tubes, of course, last for decades, while output tubes are more prone to wear, but NOS will still last substantially longer.
I’ve had many new-manufacture tubes go bad within a few days or weeks, and don’t even get me started on new power and rectifier tubes blowing like cheap lightbulbs.
For ultra-high gain players, though, NOS may be too smooth. They might prefer modern tubes that the circuits were designed to take advantage of. So as with everything tone-related, YMMV.