NOS Tubes--Are they worth it? or accurate?

After doing considerable investigation, I question whether it is worth it to undertake the quest of finding NOS tubes. Just looking at the volumes of discussion on audioasylum about Amperex 6922's and how many of them don't sound that good, the fakes out there, the difficulty in confirming how much use the tubes have seen. It just seems like way too much to deal with.

I know many will say, buy from the reputable tube dealers, but at what cost? Is their inflated pricing worth investing into something that has a limited life and can quite probably never be replaced? I think that looking into current production tubes that sound good would make a lot more sense.

The other issue is that many of the amps and preamps we are using them in are were not designed around the sound of these NOS tubes. If you substitute another tube, I think you are drastically altering the sound from the designer's attempt towards his version of reality and accuracy to something that is totally unrelated to this man's intentions and work.

It seems that we then end up with a mish-mash of sonics that are tailored to an individual's preference and may be far, far removed from any accuracy at all.
Tailoring your systems sound by changing tubes can be very rewarding, although I've relied on experts for tube recommendations and have only purchased tubes from reputable dealers. I think they are probably getting better at NEW tubes than several years back, but I've had good success both with NOS power tubes in amps, as well as NOS preamp output tubes. Hey, it is part of the fun of messing around with the glowing bottles. I heard a more refined sound, and considered it a good investment towards audio bliss.
Hi Saxo; interesting thread: Paragraph by paragraph:
1. I agree and prefer to not buy tubes from anyone except a reputable dealer, and am willing to pay the price-- some of which is for piece of mind.

2. I found a type of NOS tube that sounds great in my pre-amp, and it was worth it to me to then buy 3 full sets (6 tubes/set) at $150. per set. If I could find present production tubes that I liked as well, I would certainly purchase and enjoy them-- assuming an acceptable price.

3. As you are the tube component owner, you only have to please yourself. As long as the replacement tubes (new or NOS) are electrically compatible with your component, choose tubes that YOU like and don't be particularly concerned with what the designer was aiming for. Afterall, he was probably trying to please as many people as possible. Only you can decide what is pleasant to you.

4. The designers idea of sonic accuracy may not be the same as yours. Further, the designers tube component may sound different with your components/speakers/wires/room than it does in his design system. Also, you may choose to deviate from absolute sonic accuracy (whatever that is) and choose something that is more pleasant to you in your system.

Personally, I like a somewhat warm, timbrally rich, full bodied sound because that's the way music sounds to me (I don't like that big bloomy, euphonic sound that some tubes produce). But some like a leaner more detailed-- or other sonic presentation-- there's no accounting for taste! When a professional reviewer describes a component as "accurate", take it with a grain of salt IMO. Only you can decide what is accurate and pleasing to you. Cheers. Craig
No one said adopting tube amps is easy. Finding tubes that work well is a demanding undertaking, especially with the NOS's. Some that you find are gems, some are dogs, some work well with this but terrible with that, some die quick and painless, others explode in a great fanfare, and so on. But this is part of the hobby which, in a mad way, is what the fun is all about. Much like a high maintenance girl friend.

BTW, amps are not designed around NOS tubes because their availability and quality cannot be counted on as being consistent enough to be used in a product line.
Yah they are worth it if you are willing to accept dissapointment now and then. You may not hit it on the mark the first time,so be patient and use dealers with good feedback or people you trust to deal with.
When designing these peices,manufacturers use tubes that are currently available,due to cost reasons,and sound consistencies.Manufacturers must have to have on hand many replacement sets available to customers,so thats probably why the must use generic tubes.
It is fun to try to squeeze out more performence,but its at a price. Time and Money!
I've been playing around with tube amps since I was in high school 35 years ago. I've owned dozens and have designed and built around 8 or so (I have degress in electrical engineering and physics). Garfish's points are all accurate.

Speaking of accuracy, what makes you think that the original manufacturer had any special direct line to accuracy. Most high end equipment is "voiced" which means the engineering ends and the subjectivity takes over.
On asylum, this very topic came up, and someone posted that the old NOS tubes had somewhat different electrical characteristics than, say Sovtek 6922s. So, yes, you are distorting the original design parameters by putting NOS tubes in. Contrary to your claim, many manufacturers state that they do strive to design for accuracy as well as sonics.
To Saxo:
Individual tubes from the same manufacturer have slightly different electrical characteristics. Hence matching on various parameters. If "many" manufacturers strive for accuracy in their tube designs, which I doubr but I'll take your word for it, I would have to say that since every piece of tube equipment I have ever heard has a noticable sonic signature, that those manufacturers have not succeeded.
Pls 1, since you have engineeering background, do you believe that it is not possible to design an accurate tube amp or preamp? If, for example, you look at bench measurement frequency response on a Sonic Frontiers Power 2 or 3, you will find almost a dead flat response. You don't see that very often in tube amp reviews, I know. However, again, into an actual load, who knows? But doesn't that apply to transistor designs as well?

Regarding the SF amps, from my experience and everything I have read, listeners still find there are deviations from flat in these amps. Maybe I'm answering my own question here. That we don't know how to design a truly accurate piece of equipment.

Be that as it may, it still seems that pieces that show gross frequency response deviations show these dips and peaks in their sonics as well. So, what do measurements tell us? Something and nothing both.
You raise some good points. I've got a bunch of client stuff over the next few days so it will take me some time to get my thoughts together for a more complete answer.

In the mean time a quick response. I am fairly fanatical about flat frequency response and correct phase/impulse response. I own Dunlavy SC-V's and use wall treatment and a Sigtech Digital DSP to get very flat reponse.

The Speaker/room combo is usually never anywhere close to flat. Almost every amp is virtually ruler flat compared to that or to a cartridge. If you care about accurate frequency and phase reponse the speaker/room combo is where to start.

As far as measurements on electronics, it gets interesting when the steady state sine wave measurements are replaced with impulse measurements.

In theory a simple triode amp in a well designed circuit should be linear over its designed operating range. In practice it never is.

For example, the instantaneous whap of a bass drum may drop the voltage on the B+ rails that powers the tube so severely that for the instant the amp is operating nowhere near in spec. This can be detected with a 'scope and heard as a congested sound.

Some tubes are very microphonic, that is they vibrate when disturbed. In a guitar amp, this creates a desired sound that isn't "accurate". Loud music may cause vibrations in the audio amp coloring the sound.

These are just two of the dozens of these readily known departures from a completely "accurate" amp. All real world amps have these faults to some degree. This doesn't even count all of the depatures from linearity that happen through the electrical interaction of the speakers, crossovers and the amplifier playing real music.

Some faults, like even order harmonics in a SET, can be perceived as euphonic. There is no accurate mapping from the engineering circuitry to auditorily perceived accuracy. Our ears are non linear transducers. Evolution has tuned then to be amazingly sensitive to some signals and insensitive to others.

The reason "Reference" models cost so much is that every component and build decision is (should be) made around minimizing every possible fault with the hope that then the amp will be perceived as accurate. (Plus they are usually hand built in single digit qualtities).

At what point you find the sound acceptable becomes a matter of taste. Hence my comments on NOS. Your ears will detect sonic signatures from virually any piece of tube equipment. A designer who listens only to small jazz ensembles is of no use to be personally because I listen to large scale orchestral music.

More later
Good point about the designer's musical tastes. Designers should really become intimately knowledgeable of the sound of a full orchestra as well as a jazz band, a jazz ensemble, vocalists, choirs, etc.

I guess those who think they have achieved 'accuracy' are fooling themselves as our technology and knowledge is far too limited to accomplish this.
It sounds like you are trying to talk yourself out of upgrading the tubes. Stick with what you have if you are happy. If you find you want a little more (as most of us do) then I highly recommend upgrading the pre-amp (small signal) tubes first. It does take some research. Different tube types, different manufacturers, different amps. My pre-amp only has 4 tubes so I replaced the entire quad with a matched set from a reputable dealer here on A'gon. There was a dramatic change in sound. All the good things you read about NOS tubes. Try to find ones which are matched, tested for noise and microphonics.

I'm sure that amp designers would use Mullards, Amperex or whatever NOS style tubes if they were currently being produced. I think that MF bought up the world supply of Nu-Vista tubes so they could make a limited production run. They simply can't sell a product where the tubes are in increasingly short supply.
Everyone has very good points. I would like to add that I have NOS tubes in my ARC gear but after much research and confusion, bought them from Kevin Deal at Upscale Audio.
He knows what works and sounds best in many brands and is very good to do business with. I bought some Amperex
off ebay and never received them, so beware and buy off a reputable dealer. The tubes are worth every penny and for the improvement in sound, a steal. IMO if it sounds good, it is good!
Pls1- Wow, a terrific response. If this is your quick off the cuff remark, I want to read more later. Lots to think about.