Tube Characterization: 6DJ8, 6922, 7308, CCa, etc

Your responses to this thread, even those in opposition to my ideas are very much appreciated. There is some great information and some true audiophile wisdom here. I've even decided to purchase an integrated for a second system with 6SN7 tubes at the preamp stage.

Though I would concede that there may be no absolute basis for tube selection because of differences in circuitry, there are certainly preamps out there that expose similar qualities in particular tubes. (if my mullard and telefunken tubes sound the same in my preamp as yours, it's probably likely that every other tube will expose similar qualities in my preamp as in yours)

I have come upon a tube that I would like to share with you (with fellow DK owners for sure) that I feel is absolutely amazing and it's a Valvo E188CC. The person who sold it to me claimed it to be a Mullard, but it doesn't look like any other Mullard I have ever seen. The midrange and highs are neutral and transparant and the bass is close to if not the best I've heard. I highly recommend auditioning this tube if you can.

I've continued this discussion on audio asylum on recommendation and have received some quite interesting information there as well. Thanks again for your input.

Mrtennis, you might reread the caveats I included earlier. However I might also point out that this experience is from working with literally thousands of tubes. I do agree that the tube type ought not be the criteria for selecting a component, although I would hesitate at buying any new component that uses tubes that are out of production or doesn't sound right with current production. That is one reason we switched to 6SN7s- the current production sound much better than the current production 6DJ8s.

Of course, we have our own reasons for thinking that we have a handle on transparency that allows us these judgements :)

FWIW we tried several types in circuits that were identical in topology, but optimized for each tube. The differences became very clear.

gentlemen:

how can a statement regarding the sonic characteristic of atube be independent of a tube circuit ?

not all 6sn7 tubes sound the same and not all 6 volt tubes sound the same, provided a tube circuit is tube sensitive.

there is sufficient variation within tube class to render a generalization stating a "generic" tube sound not a good basis for selecting a component.

Ah- OK. The 6SN7 will *generally* offer you smoother sound with less 'hash', especially at higher volume levels where airbourne vibration can affect the tubes. Detail will be the same and 6SN7s will generally allow you more drive ability as they will handle higher currents better than 6DJ8s. Lifespan seems better too. The 6SN7 will make less gain, but often that is not an issue in driver circuits, line sections or DAC outputs.

Another way to describe the difference is that circuits with 6SN7s sound more refined, while those with 6DJ8s sound more brash.

Okay, curiosity got the better of me and I had to see what was going on in this thread. Albert, as you know, I do value your opinion and will no doubt be calling you at some point.

Many of us, certainly tube users, choose sound produced by circuits employing tubes because to us they are different if not preferable to the sound produced by all solid state circuits (with a few notable exceptions). We could call this particular class of sound “the tube phenomena.” We have come to this choice through observation and analysis. My hypothesis is that design engineers employ tubes because of their inherent sonic qualities and not because of electrical parameters that can otherwise be achieved by solid state devices which are cheaper and generally accepted to be more reliable. It would logically follow that these design engineers would want the full measure of benefits that can be derived from the device around which they are basing their design. Wouldn’t you? I know I would. Now you may choose to agree or disagree with my hypothesis but without some conjecture there would be no basis for experimentation. Without experimentation opposing opinions are themselves mere conjecture. Every opposing opinion I have seen in this thread is logical and valid. Does anyone have evidence to support these views? If you do, I would like to investigate whether or not there are certain classes of circuit design (as i suspect there to be) that can be identified by a certain design approach and if “common” designs yield similar sonic results based on a control tube. If we can then name these circuits and identify them within our own equipment, perhaps through consultation with the engineer we would then have a testbed. The idea is to agree upon what we can prove and bring this noble quest closer to fruition for the greatest number of people. If it finally comes to having to share my findings only with other DK Design owners then so be it. Though opinions would seem to lead in that direction, hard indicators do not.

I suspect that some manufactures choose some particular tubes due to cost, reliabilty, market perception, ease of use, and especially avialability, as well as "inherent sonic qualities".

Okay, curiosity got the better of me and I had to see what was going on in this thread. Albert, as you know, I do value your opinion and will no doubt be calling you at some point.

Many of us, certainly tube users, choose sound produced by circuits employing tubes because to us they are different if not preferable to the sound produced by all solid state circuits (with a few notable exceptions). We could call this particular class of sound “the tube phenomena.” We have come to this choice through observation and analysis. My hypothesis is that design engineers employ tubes because of their inherent sonic qualities and not because of electrical parameters that can otherwise be achieved by solid state devices which are cheaper and generally accepted to be more reliable. It would logically follow that these design engineers would want the full measure of benefits that can be derived from the device around which they are basing their design. Wouldn’t you? I know I would. Now you may choose to agree or disagree with my hypothesis but without some conjecture there would be no basis for experimentation. Without experimentation opposing opinions are themselves mere conjecture. Every opposing opinion I have seen in this thread is logical and valid. Does anyone have evidence to support these views? If you do, I would like to investigate whether or not there are certain classes of circuit design (as i suspect there to be) that can be identified by a certain design approach and if “common” designs yield similar sonic results based on a control tube. If we can then name these circuits and identify them within our own equipment, perhaps through consultation with the engineer we would then have a testbed. The idea is to agree upon what we can prove and bring this noble quest closer to fruition for the greatest number of people. If it finally comes to having to share my findings only with other DK Design owners then so be it. Though opinions would seem to lead in that direction, hard indicators do not.

Tvad and Neebee, there is no doubt that I support my design decisions !! :)

-And the reason that I made those decisions is based on the experience that I had with the tube types I mentioned. The 6DJ8 was a popular intrumentation tube (look in an old Tektronix scope sometime) and is very good in that application. Unfortunatly, the tube was not originally intended for audio and while it is very linear, it has a micorphonic tendancy that is profound relative to other tubes.

Despite that it has been popular in audio for a long time. However if one pays attention to what it and other tubes do, it will be seen that any equipment that uses it will have a coloration particular to that tube- you all know what I am talking about. The fact of the matter is that audio (high end anyway) equipment ought to have *no coloration at all* so if you want that you will have to start with a less troublesome tube. It really is that simple.

I was influenced to try the 6SN7 after seeing the the MFA Luminescence preamp (which was extraordinary in its day) as well as the Vacuum Tube Research Labs stuff. It was easy to discern why the tube had/has a serious following.

So I was just letting you in on what I have found to be true over the years (I think most of the more respected people posting here do exactly the same). I hope this is not troublesome.

Tvad, I suspect that Atmasphere is just supporting his design decisions, thats all. He put his money where his mouth is, but we don't have to. :-)

Interesting thread. For myself rolling tubes is a distraction which keeps me from endlessly spending big bucks on buying, trying, and growing dissatisfied with electonics, wires, PC's, ad infinitum. Just another aspect of the hobby. I try to entertain myself by rolling tubes and playing with room set up. Much cheaper and more fun. To each his own. I can understand why someone would want a near definitive list of tubes, applications, elcetronics speakers, etc, but I think there is a certain amount of mental masturbation involved in thinking that actually accomplishing such a feat was possible. Oh well.....

Thanks to everyone who contributed kindly and thoughtfully to this post.

Jab, Cmo, Dopogue, Imin2u, let's move forward. I will repost a part II to this thread in hopes that we can consolidate those of like opinion in this forum. If not I will try to find some other way to invite your participation. I'm planning out a methodology with a speaker designer so when we have a plan of attack I will let you know. Look for: Tube Characterization: 6DJ8 Part II

In the meantime Albert, please feel free to basterdize this thread to your hearts content. The rest of us will be somewhere else. I guess spending an hour on the phone with me discussing audio at 3:00 in the morning was not so much personal generosity as insomnia. Sleep well!

In the meantime Albert, please feel free to basterdize this thread to your hearts content. The rest of us will be somewhere else. I guess spending an hour on the phone with me discussing audio at 3:00 in the morning was not so much personal generosity as insomnia. Sleep well!

We can speak on the phone if that is of value to you. My comments to Ralph are due to our 20 year friendship.

Thanks to everyone who contributed kindly and thoughtfully to this post.

Jab, Cmo, Dopogue, Imin2u, let's move forward. I will repost a part II to this thread in hopes that we can consolidate those of like opinion in this forum. If not I will try to find some other way to invite your participation. I'm planning out a methodology with a speaker designer so when we have a plan of attack I will let you know. Look for: Tube Characterization: 6DJ8 Part II

In the meantime Albert, please feel free to basterdize this thread to your hearts content. The rest of us will be somewhere else. I guess spending an hour on the phone with me discussing audio at 3:00 in the morning was not so much personal generosity as insomnia. Sleep well!

Hey Ralph! I need to call you.

Hope your going to attend Rocky Mountain again this year, you can spin some more new music. I bought that Shins "Chutes Too Narrow," LP and still trying to get into the new Bjork.

my experience with the Audionote CD2 and the VTL Deluxe 120 amplifier has confirmed that changing tubes can affect an audible difference.

the CD2 uses a 12 volt tube. it is a 1990's design CD player. I have treid 12AU7, 12AT7, 12AY7, 12AX&, and 5751.

i currently use a GE 5751 black plate.

the VTL uses 12AT7 input tubes. I prefer RCA 12AT7 black plate or 1960's Mullard.

the VTL is a design from the late 1980's.

It is possible that the older tube designs are more sensitive to tube changes, than current production tube products.

Again, i believe the circuit design is key.

Here's another example. I had a Cary AES preamp. I tried many NOS 6SN7 tubes, hardly noticing a difference in performance.

Thanks for your input Tvad!

I agree with Albert too. Having said that, I will now proceed to step on some toes so please excuse me for a moment :) :

6DJ8/6922s are not a good tube for audio despite what you might hear here. The reason is they have a tendancy to microphonics (they were built more for instrumentation and not audio), despite their otherwise excellent characteristics. You *really* have to hunt to find one that is low microphonics. The 12AT7 is a lot easier to use and so is the 6SN7 for many of the purposes that you might use a 6DJ8 for.

The 6SN7 is the octal equivilent of the 6CG7, but is usually smoother sounding because again there are less microphonics (my guess is due to the more robust structure).

12AX7s can be very nice but do not expect a wide bandwidth circuit! So from 12AX7s you will get an older-fashioned tube sound as mid and treble artifacts will be audible due to phase shift caused by the upper frequency cutoff. Its not a bad sound- just not very fast. Incidently this is something that 6DJ8s do better (they have plenty of bandwidth) but now you have an 'iridescence' caused by their microphonics.

12AU7s can be very nice as they have good bandwidth, but they are more prone to microphonics again, however with less of the 'bell ringing' issues of the 6DJ8 family (which includes the 6H30).

IF it seems that microphonics is a major problem, you are right. Tubes designed for audio do seem to have less in that department then those designed for instrumentation. There are other more subtle effects caused by means of construction, some of which are lost to time: Telefunken 12AX7s and Mullard tubes are sought due to the excellent contruction techniques employed during the hey day of tubes.

So, while I have offered some general pointers on some tubes, the individual tubes of the specific types will vary enough for considerable overlap! This is why Albert is correct in his assertion. If you are dealing with the best of the best in all tube types you will find them all very close. It is the generel average tubes where the foibles that seperate them become evident- for example the average 6DJ8 will sound pretty bad compared to the average 6SN7.

My advice if you are tube rolling is to be careful about documenting what you are doing, and make sure you can return tubes that you buy from NOS/antique dealers! *Above all* remember that you are supposed to be having fun and don't go off the deep end. Its not pretty :)

08-01-06: Mrtennis
"this question can only be answered in the context of a particular tube circuit".

08-01-06: Rchau
"You can change the sound of tube by just changing the operating point (plate voltage, load ressistors, heater voltage,...). Also, the sound in different topologies(anode follower, cathode follower, cascade, mu follower, etc..) vary with the same tube".

This is the first issue that needs to be addressed: Can anyone offer confirmation that using the same tube (control) in a number of different preamps radically changes the latent sonic characteristics of that tube or will there remain a distinct signature? It seems to me that a designer creates a tube amp or preamp not because of the electrical characteristics of tubes(you can accomplish that with solid state devices) but rather for some sonic quality inherent with tubes. A tube isn't just another circuit in a device it is "the" circuit in the device and engineers design the ancillary circuits in support of this all important part. I know that I'm out of my depth here but this idea would seem to be supported by Mick Maloney of Supratek and my guess is most other design engineers as well. If indeed your tube component is virtually immune to tube rolling, then it's a moot point. If on the other hand, your sound changes considerably with changes in tubes then you are the most likely candidate for this study.

How, in one breath, can one laud the accomplishment of Joe's Tube Lore and in the next breath invalidate the concept? Let's face it, this classic post has probably generated more tube interest and more tube sales since its release than any other single contribution. Personally, and based on my limited testing of 4 sets of tubes, I have found his objective observations to be spot on and his equipment doesn't even resemble mine. That's why my reaction was, 'hey let's run with this'.

I think Albert Porter is the most generous and one of the most knowlegeable persons in this hobby. I'm hoping that just because his post was in opposition to mine that we're not creating camps. I'd guess that upon the additional information and further reflection, he would incline more towards the "okay if we want to do it, this is what we would have to do" side and this is what I would like to encourage. I'd be very interested to know the vernacular Albert uses in his listening sessions with his friends of invite anyone to recommend such a language, perhaps something used by their favorite reviewer. This could be the Audiogon standard. We can also use existing reviews as a launch point.

You either believe that tubes make a difference or you don't. If they do make a difference, then shouldn't we seek to objectively evaluate and bring closer to science our selection process. than exists currently. Perfect? hardly. Science? sorta. Vauluable? invaluable!

I have over 100 hundred pairs of this series of tubes. In the past year I've listened to plenty but not all. One problem you'll find is that most take days to have their signature sound settle.

Regardless, I'd be willing to participate in this experment and am "all for it".

Mrtennis - When I owned the BAT P10 a few years ago, I never got around to playing with the many different tubes like I did after I got the Aesthetix Io. So I have no experience that may or may not match your findings with the P5. It may very well be insensitive to tube changes ..... BUT .... have you tried the Tele 6922/6DJ8's here? And what about the Mullard 6922?

After reading Albert's numerous details on tube trials with the Aesthetix models, I wasted no time to play with this for the Io. And as much as the stock Io was far beyond the stock P10 in how in rendered 3-dimensionality and decays, the Mullard and Tele tubes took this to yet another level. And when I got the Aesthetix Callisto, I went back to read Albert's tube experiences and found nearly identical results in my system with this. The only thing that I have learned recently is that a strategically placed pair or two of Brimar 12ax7's in my system can add just a little more foundation on the bottom end, and a little more sparkle on top with just a tiny bit of midrange magic loss from displacing the Teles. It's all about fine tuning to a personal "balance".

With knowledge on how incredible the Tele 6DJ8 was in both Aesthetix models, I discovered how far it took the Wolcott amps as well as an older Counterpoint NPS400 amp. A pair of these alone has improved each component significantly.

As much as Ken Stevens likes to run with Sovteks in his preamp and amps, I found the Mullard 6922 and 12ax7 to take the JL-3 amps far beyond the Sovteks in terms of tonal coherency which results in a more natural (not edgy) top end. I did however try several different 12au7's here and could not hear a difference. And I had similar findings when I had the CAT Ultimate II on loan for a few months to compare to the Io/Callisto. Some people have reported they did not like the Mullards into the CAT preamp at all but it was a major improvement over the Sovtek in my system.

My system's resolution took on a huge boost when I put in a power line conditioner. This followed with power cable upgrades throughout makes tube differences even greater. But even nearly 20 years ago when I owned the ARC SP-10, I remember the RAM tubes that I put in this made quite a sonic improvement to the tubes from ARC. And when I sold the SP-10, I kept those tubes and used them in the LS5 and got the same benefit over the stock ARC tubes. No doubt improved system performance makes these differences even greater. But 20 years ago, my system was not known for detail and resolution and yet tube changes in the SP-10 were not subtle.

So unlike your lack of success with tubes bringing on significant changes, my hodge-podge collection of components over the years, from many different manufacturers, has given me quite different results. I'm kind of a midrange textures, harmonics, ambience, bloom, decays, etc., fanatic, so this is what I listen for with tube trials. Many systems out there lack much of this magic and in such cases, these differences might get lost in the wash.

And thanks Ecclectique.

Amen Jafox. Very well said, and Kudos to Photon as well.

Bartokfan, one important thing to remember about tubed new gear is that a manfacturer has to be able to depend upon a reliable supply. I'm sure that most manufacturers would prefer to install 60's Amperexes, Siemens, or Mullards instead of Russian variants if they were available in unlimited supply at a reasonable price. But that isn't going to happen, so they have to install what's available. A number of smaller manufacturers do offer upgraded NOS tubes as an option if you want to pay for them. As to the effects of tube rolling being too subtle to make it worthwhile, it's a matter of perception. To my ears, the difference in sound between a particular pair of 6922 Phillips Mini-Watts and a pair of 60's Amperexes in my phono stage is hardly subtle, but hey, to each his own.

hi jafox:

i find that many tube circuits do not respond to changes in tubes.

for example, a jolida cd player and bat vk d5 did hardly changed their performance when i inserted a variety of nos tubes.

some circuits are relatively insensitive to changes in tubes.

i had a similar experience with a cary cd player.

My tube rolling experiences with many tubed-based components is polar opposite to the comments made by Bartokfan. What exactly are people trying to wiggle out of? Quantifying how each and every brand/model tube will sound in each and every component? Sorry, but as Albert already alluded to, it's just not that easy.

In some cases, the differences can be subtle. And in others not at all. There have been times where a single pair of tubes changed in a component resulted in greater refinements than I had achieved in past component upgrades that costed far more. If all you hear time and time again is a subtle change, that indicates the limitations of the component or system under evaluation and not the process of comparing tubes.

From what I have learned with trying various Mullards, Telefunkens, Brimars, etc., EL34, 12ax7 and 6922/6DJ8 tubes, I would never make final judgement on any component that contained Sovtek tubes. These things are mediocre at best. No master audio engineer can resolve this with fancy capacitors, point-to-point wiring, teflon boards, chassis dampening, 18 stages of regulation, etc.

As for what tubes the designer puts in a new product, obviously new off-the-shelf tubes are the only option due to availability and guarantee issues. But with very little effort, many of us hear components perform at levels even their designers never heard.

Bartokfan, you are free to keep the stock tubes in your preamp all you want. And this is good news to the rest of us as there is one less person to compete with when a good deal on older tubes becomes available. But do not condemn the efforts and experiences of others who have significantly different results than yours. And to claim it is nonsense clearly indicates you have a lot less experience with this process than a number of Audiogon members whose reports in these forums echo mine to a T. Afterall, you are into component rolling while the rest of us do it at the tube level.

What I find silly is to go through preamp after preamp, amp after amp, etc., the cost of shipping and potential for damage, until I find a stock unit that meets my goal. Sorry Bartokfan, but it is not that simple...it is naive. I'd rather purchase a few pairs of tubes that cost me $10 or $20 to ship, try them in my system, keep the ones I like and put the rest back on the used market. Now that's simple. It sure beats packing and shipping 50-100 lb components around the globe.

Through the sharing of tube-rolling knowledge by others with the same components as mine, I have taken my system to a performance level that I never knew possible with these components. Rather than put a negative spin on this and call it a silly game, I think of this as a continued quest for refined magic.

Yes, worthwhile indeed. I would personally be interested in hearing from anyone with a Conrad Johnson Premier 17 about tube experiences. I'm currently using Mullard E88CCs with a back-up quad of Amperex/Holland 6DJ8s and would be quite happy with either. Dave

this question can only be answered in the context of a particular tube circuit.

it is difficult to generalize because circuits differ, even discounting the variable of differences in perception of sound.

You guys might want to check out issue 7 of Vaccum tube Valley (VTV). An analysis of about 26 different versions plus a history of the development with pictures of versions from different eras.

In VTV has done such test on a number of tube types. I don't necessarily agree with any of them but it is basically what this thread proposed.

BTW-I think this endeavor is fruitless. You can change the sound of tube by just changing the operating point (plate voltage, load ressistors, heater voltage,...). Also, the sound in different topologies(anode follower, cathode follower, cascade, mu follower, etc..) vary with the same tube.

Hey anacrusis, give up your quest for accurate infor on a specific model of tube characterists.
I've tried and have had little luck. You raise a very good question that everyone wants to wiggle out of.
I personally do not go cahsing after a "magical tube". Obviously I leave that decision up to the designer of the amp. If i get the amp and it fails to deliver what i need in my muisic, away she goes.
On the tech topic i asked what are the general characterists of the following tubes 6550, Kt88, KT90, EL34.
Received one good answer, Others were vague and elusive. not straightup.
You are right , by replacing a few tiny pre tubes, you may give up one slight characterist in one, for another. But almost always too subtle a change to notice.
I thought about rolling the 4 russian 6922's in my Cayin 17 cdp, but guess what, I'm not. The designer put them in and thats where they'll stay.
If i get a tube amp, and don't like the sound, i'm not going to "roll" the tubes to get better sound. To me thats nonsense.
Just dump the amp and get one you like better.
its that simple.
What a silly game "tube rolling".

I've found TFK 6DJ8s to be accurate, linear and true across the frequency range. Mullards are nice but a little warm to my ears in my system. It's not really what this tube sounds like versus that, it all depends, But if I were going to make generalizations, it would be just the opposite of your observations, just my 2¢.

Happy listening,
Joe

Comming from someone who is pretty much just starting to experiment with NOS tubes I would love to have some further references (I think Joes Tube Lore is really great BTW) on the general qualities of differing tubes. I wish there was some more info on identification as well.

Chris

Perhaps I should follow Dsremer's lead and invest in good wine and forget exotic tubes. Now you may like Chardonnays for reason of their peppery quality and I may dislike them for that same reason. The peppery quality remains.

Tubes too indeed have characteristic sonic qualities as does everything else in the component chain. For instance, in the 6DJ8 family, I have never heard a Telefunken that didn't have soft, warmish sounding bass relative to say a Mullard which I would characterize as quicker cleaner, with more dynamic impact. Then again Teles have those liquid mids and highs. Though you may like what you like and that's how it should be, I doubt any of you that have experience with the afore mentioned tubes would question my objective observations. We need a peoples point of reference and a common objective language.

My system:
Porter Ports (20 amp cryo)
Eichman Express Power
Denon 3910
Synergistic Research Designer Reference Interconnect 1m
DK VS-1 Mk III:
Synergistic Research Alpha Quad Active 4m

Synergistic Research Designer Reference FX Interconnect 4m
NuForce Ref 9s
Synergistic Research Designer Reference Spkr Cable 2m

Von Schweikert VR4 Jrs

I'm using Valvo E188CCs in the DK

If you still think I'm all wet (as opposed to lucid with great midrange sparkle), I'll discontine this thread.

My post is offered more as a contribution and less as a quest for a personal solution. I propose the creation of a logical methodology for determining the sound of individual tube brands and models. This post was inspired by Joe's Tube Lore and I hope would represent the next logical step.

If we can establish a minimum reference then we benefit the greatest number of people. If I only use my personal system as a reference, I benefit maybe only one or two others.

If it can be said that a tube has a house sound then surely there are characteristics latent to the sound of a particular tube in a given context. I really don't think that context has to be as exacting as -this preamp or that preamp- because we are looking at relative values here. But you do make a good point so let me ask what you feel the minimum reference requirements would be to make valid evaluations. Let's start with the above being used as preamp tubes, and that the participants would decide on reference recordings, and that there would be a reference tube from which comparisons can be made. Do you feel that we would have to be more specific than that for the experiment to have value? Once we establish the above, we can get a consensus on descriptions that are objective and quantifiable.

My post is offered more as a contribution and less as a quest for a personal solution. I propose the creation of a logical methodology for determining the sound of individual tube brands and models. This post was inspired by Joe's Tube Lore and I hope would represent the next logical step.

If we can establish a minimum reference then we benefit the greatest number of people. If I only use my personal system as a reference, I benefit maybe only one or two others.

If it can be said that a tube has a house sound then surely there are characteristics latent to the sound of a particular tube in a given context. I really don't think that context has to be as exacting as -this preamp or that preamp- because we are looking at relative values here. But you do make a good point so let me ask what you feel the minimum reference requirements would be to make valid evaluations. Let's start with the above being used as preamp tubes, and that the participants would decide on reference recordings, and that there would be a reference tube from which comparisons can be made. Do you feel that we would have to be more specific than that for the experiment to have value? Once we establish the above, we can get a consensus on descriptions that are objective and quantifiable.

I also feel that one of the pleasures of tube rolling is the variation of different nos tubes in different applications. Many nites are spent in trying different brands and or different "levels" of tubes CCa's, PQ's 7308's and so forth in my tube equipment, with friends who may or may not agree with my favorite. One thing is for sure the tubes all start to sound better by the second bottle of wine.

>>Does anyone agree with me that there should be detailed descriptions of the sonic characteristics of each of the popular versions of each of the above tubes.<<

No.

What you wish could be stated with absolute certainty is not possible, in my opinion. There is too much variation in sound, even when the exact SAME tube is auditioned in two or more pieces of equipment.

Depending on design, a 6922 type tube might be used as input, phono gain, intermediate preamp stage or output buffer in a CD player. Then throw in various associated equipment, personal preferences and the fact that two NOS tubes aren't necessarily equal (even if they test good) and you get the idea of how difficult this is to nail this down to an exact science.

Joe's tube lore is written by a good friend of mine, we speak almost every week. We were just discussing this topic a few days ago and remarking how difficult is it is describe sound when the teller and listener don't know each others personality and preferences.

Fortunately I have a large group of people I've listened with, making it easier to come up with language that applies to things we've listened to together.

To give you a possible solution to your question. Best if you outline your own system, personal preferences and what tubes you've tried. Audiogon members that have similar experience will share their opinion. I find that usually, the comments posted here are extremely helpful (and accurate), an excellent way to establish your own references and favorites.