Tube Characterization: 6DJ8, 6922, 7308 Part II

This is a continuation of the thread:
Tube Characterization: 6DJ8, 6922, 7308, CCa, etc

This above thread was dense with information regarding tube selection, classification and characterization but like many threads, branched off into more specific areas of focus. Though I would definitely refer to this original thread as a point of reference, what I would like to do here is condense much of the information specific to it's original intention. The objective evaluation of 6Dj8 family of tubes.

One of the most thoughtful responses and one for which I am most grateful is:
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
To this end I have decided to cool my jets a little and take a more moderate approach.

The questions are:
1) Can a tube within an audio component be evaluated for its sonic qualities or will the associated circuitry be so influential on the sound that such an evaluation would be pointless unless put into a specific context (ie the same preamp)

2) Will a tube retain enough of its sonic signature with specific components or specific circuits to make such an evaluation fruitful?

3) Is there an objective language or terminology that we can use which will make such an evalutaion comprehensible?

Many of the most experienced audiophiles in this forum feel that it can not be done, at least meaningfully. A number of others feel reservedly that it can and a few are of the opinion "let's give it a go". Some just find pleasure in trying out different brands on a casual basis(a very sane point of view imo).

Some contributers feel and for good reason that the manufacturer used certain tubes for good reason and that tube rolling would just be making trade-offs. If you want a different sound, buy a different preamp, cd player, what have you.

Before anyone undertakes such a study they should refer to the existing information contained in "Joe's Tube Lore", and evaluations done by Vintage Tube Sevices, VAC, and Vacuum Tube Valley, especailly issue #7 (thanks to Jab and Rchau). Consider that some components are just more sensitive to tube changes than others. Lastly, be sure that you can return, at least exchange tubes for

One comment by Atmasphere I found particulary interesting was his assertion that:
If you are dealing with the best of the best in all tube types you will find them all very close.
and also adds that the 6SN7 series of tube is iherently better than the 6DJ8 series and to me supports the idea of just changing preamps. By the way Raymond Chowkwanyun of enjoythemusic does a capsule review of this tube type:

There is also a strong contingent of contributers that feel nos tubes are inherently better sounding than nns tubes. At the prices some old stock tubes are going for I find it difficult to believe that a modern tube manufacturer can't duplicate or even improve construction methods producing superior tubes and still make a nice profit but that so far does not seem to be the case.

Imin2u, if you are still interested, may I suggest starting with some of those tubes you have that haven't otherwise been reviewed and we can start putting them through their paces. We can move from there to confirming existing findings.

I invite anyone who would like to be a part of this experiment to tell us a little about the sound your favorite 6DJ8, what you use it in and if you'd be willing to run other tubes through your system.
I have one more reference that might prove interesting.

Eric Barbour, formerly of Svetlana, wrote an article comparing different types of preamp tubes.

Eric built a special preamp that could take almost any small signal triode (circuit is detailed in the article). He offers comments about all types of the preamp tube. Let's just say Eric offers his 'opinions'. Not an easy read if you are a 6DJ8 fan but a happy one if you are a 6SN7 fan.

The article was the feature article in Glass Audio, Volume 9, Number 6 1997. This artcle floated around the internet a a few years before that issue came out.
at this point my preferred 6 volt tube is a mullard 6922 white label, vintage, late 1960's. however, it is preferred marginally to other tubes.

the bat cd player uses 6 6922, i have 1 pair stock 6h23, 1 pair 6dj8 yugo and one pair 6922 mullard.

i assert that most current generation components are not tube sensitive. rather it is a design from the 1980's and pre 1980's that is more likely to be sensitive to tube changes.
Providing my usual general, nebulous, and generally biased views here's a quick response to yr quests:

1) Judge in specific context. You can extrapolate only when the circuits are similar. (There's not much creativity, anyway).
2) Oh yes -- see the abundance of comments. Mr Tennis above being one. The point is, in using a specific tube there is a specific circuit for that tube: the circuit will follow the tube's characteristics and properties -- with some differences fm one product to another. That's what I mean by "similar" above
3) Dunno, really. Some of the things we want from a tube is a good linear operating region, ease of application, frequency extension in audio applications... but how to translate that into end results is beyond me...

Another point: there are some applications (i.e. circuits) where you design around the tube and others where you choose a tube to "fit" the circuit. For example, say you need a low mu for your whatever; the 6sn7 will be difficult to integrate.

As to NOS tubes: they are generally better constructed (quality control, better tolerances). Remember that tubes were a mainstream component at the time for audio applications, so product quality had to be dependable.

I came to the conclusion that the octal tubes are better by listening to systems that use both. The 6SN7 is a great driver/preamp tube.

Ah ah ah, Mr Tennis, don't get too ahead of yourself on assertions. There are many current models that respond significantly to tube changes. Could it be the resolution of the system used to evaluate the components and not the specific component under test that result in subtle or no differences you hear with tube swapping?

As for the 6922/6DJ8/7308, as much as I like the Mullard 6922 gold pin, the Telefunken 6DJ8 has been phenomenal in every component I have tried. Tonal coherency is more refined over the somewhat edgy Mullard in the treble, and the Tele portrays an awesome piano bloom while retaining the articulation from note to note. This has been consistent with every preamp and amp I have so far tried. No other tube has given me the same results with each product under test. Ironically, the Tele 12ax7 affects components very differently from model to model.
Jafox, I'm interested in trying a pair of Telefunken 6DJ8. Having never purchased a pair, I'm interested in any tips you could provide regarding what to look for, i.e. getter type, construction, date codes, etc.

I have a couple pairs of 6DJ8/6922 tubes (National/Matsushita 6DJ8 - sourced from VTS, Mullard 6922 - Mitchum 1967 & 1968) I'd be willing to offer in partial trade for a good pair of Telefunken 6DJ8.
Jafox, regarding:
As for the 6922/6DJ8/7308, as much as I like the Mullard 6922 gold pin, the Telefunken 6DJ8 has been phenomenal in every component I have tried. Tonal coherency is more refined over the somewhat edgy Mullard in the treble, and the Tele portrays an awesome piano bloom while retaining the articulation from note to note. This has been consistent with every preamp and amp I have so far tried. No other tube has given me the same results with each product under test. Ironically, the Tele 12ax7 affects components very differently from model to model.

A perfect example where these two tubes can swap performance is the top Aesthetix pieces, the Io and Callisto. The Tele works wonders in the Io phono but sounds compressed and etched in the Callisto. Of course all the other tubes in the Io and Callisto also effect the final outcome, meaning swapping the 6SN7 from Sovtek to RCA, then RCA to Sylvania or (better yet) an RCA 5692, will alter the outcome of the tests of the 6922 and 12AX7 positions.

Another place where performance swaps is the Viva preamp. Stock it comes with Sovtek 6922 which works OK. The Telefunken 6DJ8 works better but literally dies (dead) in less than two months due to circuit design.

Swapping to Mullard 6922 is worse performance than the Telefunken but it will last about three months before dying. Go to Siemens E288 CC and you have sound similar to Telefunken and better than Sovtek with long life.

Still another is the input stage of the Wolcott Presence 220 mono blocks. The Mullard is king there, easily displacing the Telefunken. Problem is with the Wolcott, if either of the Mullards are off specification, the Wolcott starts up, all lights come on and then there is NO sound.

There are dozens of other examples. As I've stated before, tubes are circuit dependant as to how they ultimately perform and how long they operate at equal performance (as installed) before going bad.

The way to determine this is own the same equipment long enough, keep a log on hours and put stickers inside the equipment chassis with test scores from a high quality tester. Go back at 3 months, 6 months and a year and see how each holds specifications.

Tvad, if you want to borrow Telefunken 6DJ8 tubes for testing (no offers for trade) we can probably work a deal for me to ship you some to try. I have 6Dj8 and 6922 in Siemens, Siemens CCA, Telefunken 6Dj8, Telefunken 6922, Mullard white dot 6922, Brimar 6922, Amperex 7308, Amperex CEP 7308, Amperex Bugle Boy 6DJ8, Amperex 6922, Sovtek 6922, Matsushita 6DJ8 and several others.

If I had to pick ONLY one 6DJ8 tube of all there are and forced to use it in EVERY piece of equipment regardless of design, I too would choose Telefunken 6DJ8. Fortunately we have lots of other brands and can choose what works in each circuit, depending on design.
Tvad - I would be happy to ship a pair for you to play with but it sounds like Albert has the Fort Knox of these tube types under vault and key. I suspect he could ship you several different pairs to give you an idea far beyond me only sending the one pair.
Albertporter and Jafox, thank you. Would either one of you provide a short primer on what to look for on a Telefunken. I know, for example, that on Siemens tubes, one looks for differences in the risers (grey vs shiny), getter support construction, seams on the bottle. Are there similar clues on the Teles?
Tvad, this site has accurate descriptions and good images of most of the audio tubes we're discussing. Karsten is one of my suppliers and is located in Germany.
Outstanding, Albert. Thank you.

Of the four Telefunken varieties, which are your tubes of choice?

I use the ECC88, the 6DJ8 variety with common steel pins (not gold) pins. The E88CC is a true 6922 and I frequently find these gold pin versions (although classier looking) to be harder sounding, grainer and slightly more compressed.

Here is a link to a site in Italy with images of the E88CC Telefunken and the ECC88 Telefunken.

Here's a good shot of the Telefunkens with white bulk pack boxes in background from WiWi in Hong Kong. I just bought Telefunken 6463's and Mullard M8162 (CV-4024) from him.

Hope that helps.
Tvad: Interesting as I only have experience with the same exact tube, the single-ring getter, Albert has noted. I have a variety of Mullard gold and steel pins but only steel Teles here so I have no experience with the gold vs. steel Tele.

I bought 6 pairs of the Tele 6DJ8 expecting to put 2 pairs in the Callisto, one pair in the Io, one pair in the Manley DAC and then a pair for the CAT amps....with one spare for "unfortunate" events. And then right after ordering these I remembered the Manley used a pair of 12ax7s instead so this left me two spare pairs. And then upon trying two pairs in the Callisto, I found I liked one pair of Teles and one pair of the Mullards here. This could change upon some cable updates soon to occur, but for now, I like the one pair of each. So this resulted in 3 spare pairs.

If I only had one pair of these, it is very easy to know where they would go: the Io. But while I wait for my CAT amps to return, I use this pair in the Counterpoint NPS400 amp and was quite shocked at where this tube took the amp. I suspect few people have heard this amp perform to this level. It continues to outperform so much I have heard for far more cost. What a great backup amp. And it does not even flinch with the SoundLabs .... and it loved the Maggie 3.5s too.

When I took a pair of these Teles to a friend's home and we dropped them in his Calypso, once again, they brought on the midrange magic without negatively affecting the frequency extremes. He was using a UK tube here but not a Mullard if I recall. After hearing the improvement here, I left them with him as I owe him a ton for all he has done to help me refine my system this last year. So I still have the two spare pairs. I can ship a pair for you to play but I would like them back in a month or two unless you can not find a pair yourself. And then we can wrestle on an agreement here.


Quote from Joe's Tube Lore:

Telefunken 6922 / E88CC (with shield, diamond bottom, gold pins) Slightly hollow mids, not as rich as the best Siemens and Amperex. A bit like the Siemens E288CC, though a bit better than that tube. A good tube, but the more common & cheaper Siemens 6922s are much better choices IMO. (Absolutely pounds the Russian tubes, though!)
All due respect to Joe, his observations were made in his system, as far as I know, and every system is different. He also prefers Amperex over all other 6DJ8/6922, but I do not agree.

Thus far, I prefer Mullard to Amperex for the warmer mids...and I prefer Siemens CCa to Amperex for the smoother and less etched highs. Other Siemens are not so high on my list.

So since my experience is not entirely in agreement with Joe, Teles are worth hearing, IMO.
This was the only mention by Joe of the Tele 6922/6DJ8 and note it was the gold pin version which Albert doesn't like and Jafox hasn't tried. So far, I haven't agreed completely with Joe either, particularly regarding the Siemens Cca, which Joe likes, but he says have a slightly dry sound to them. And you are right in that he only evaluated them, I believe, in his DAC. Notice also that the only mention of the Mullard by Joe was of a pair that had died on him but he recalls that they were a very good tube.
Which version of the Mullard do you prefer? Gold pins, late 50's, early 60's? Oh, and yes, I also agree that the Tele is worth a try. I'm not trying to discourage you. Go for it!
My integrated is of new design and the differences tube rolling makes is profound. Certainly, modern speaker designs are based on classic designs. I might suggest that modern tube designs are based on classic designs ie. Cayin for instance, actually promote their products as such.

Consider the variables in the evaluation of any component. Applying the same logic used in opposition to tube evaluations would invalidate the reviews of all equipment. Anyway you slice it evaluations are the gears that move this industy and hobby forward and to completely excise tubes from this process seems to me a bit silly.

Perhaps someone just has an ax to grind...

Mullards have better bass than Telefunkens:))

Mullards have better bass than Telefunkens:))
Anacrusis (Threads | Answers)
In an effort to maintain the course you set for this thread, would you share the gear in which you found the differences in these tubes. And, perhaps you could specify which Mullard and Telefunken tubes you tried (year, construction, factory, etc...).
Tvad: Though I have listed my equipment on a previous post to which you specifically responded here it is again:)

My system:
Porter Ports (20 amp cryo)(direct to DK, Denon)
Eichman Express Power Cables
Denon 3910
Synergistic Research Designer Reference Interconnect 1m
Synergistic Research Alpha Quad Active 4m

Synergistic Research Designer Reference FX Interconnect 4m
NuForce Ref 9s (DK passive preamp stage)
Synergistic Research Designer Reference Spkr Cable 2m

Von Schweikert VR4 Jrs

I'm currently using Valvo E188CCs in the DK (which I am told are in fact Mullards) The Telefunkens I have are E88CC.

Since I don't know enough to say the year and construction, factory etc, I can post photographs if you can tell me how.

Other tube equipment I have owned:
Luxman CL-35 Mk III
Michaelson and Austin TVA-10
Conrad Johnson PV-6
NYAL Moscode 300

all of which saw tube rolling, although in those days we just called it "swappin out the tubes"
Anacrusis, I asked about the gear in which you tried the Mullard and Telefunken tubes for my benefit and for the benefit of others who might read this thread and have not read through your other thread. Admittedly, I had not committed your system to memory, and I did not refer back to your other thread to research the answer.

Thanks for the answer to my question about the gear in which you tried the Mullard and Telefunken tubes, which is the DK VS-1 Mk III integrated amplifier.

The comparison you are making between Valvo E188CC and Telefunken E88CC is somewhat apples to oranges, and I can understand how there might be a dramatic difference. If you ever have the opportunity to compare Mullard E88CC to the Telefunken E88CC, this will be a better barometer of how the two tubes stack up. I mention this only as a point of education because I know your goal was to produce a reasonably precise tube reference as they apply in a specific circuit.

FYI, if the Valvo E188CC are made by Mullard, they will have a two-line date code etched into the glass. The first line of the date code will have three characters, and the second line will have three or four characters depending on whether the tubes were manufactured before or after 1961.

The second line will usually begin with a capital R or B signifying manufacture at the Mitcham, UK plant (R), or the Blackburn, UK plant (B). The next character will be a number signifying the last number in the year of manufacture. If the tubes were made prior to 1961, then the second line of the date code will have only three characters.

The third character will be a letter corresponding to the month of manufacture (A=Jan, B=Feb, C=March, etc), and the fourth character will be a number 1-4 that corresponds to the week of manufacture. The fourth character will only exist on tubes made after 1960.

Finally, if the Valvo tube has a Delta, or triangle etched on the bottle, it is manufactured by Phillips in the Herleen, Holland plant. I have owned Valvo E188CC tubes that were labelled this way, and therefore they were Phillips tubes branded as Valvo.
Wow! I may not have the opportunity check out the Valvos till this weekend but I will and let you know. I will also look for similar identifiable markings on the Telefunkens and let you know too. I'll then give you a detailed description of the sound of each. Maybe some Sovteks and Amperexes as well

Why is the comparison I'm making between Valvo E188CC and Telefunken E88CC apples to oranges. I don't understand. Even if it is, am I not just looking for the best sound possible anyway? Please explain.

Lastly, I wonder if we are all looking for the same ideal. Even though my experiece with live music out-weighs my experience with recorded sound by a considerable margin I prefer this liquid, irridescent, intimate kind of sound. Not really what I would consider true to the original and in some ways more appealing than the real McCoy. I almost think that, in another way, some of the best solid state amps do a better job at reproducing reality. What would you characterize as ideal? Probably a topic for another thread.
Why is the comparison I'm making between Valvo E188CC and Telefunken E88CC apples to oranges. I don't understand.
E188CC and E88CC were manufactured to different tolerances, with the E188CC built to tighter specs and designed to last longer, have lower noise and less microphonics than E88CC or ECC88 tubes. Therefore, construction of your Valvo E188CC and Telefunken E88CC tubes is different...not only because they're different model number tubes, but also because they're from different manufacturers. Two E88CC tubes from different manufacturers will be more alike than an E88CC to an ECC88 or an E188CC.

BTW, ECC88=6DJ8, E88CC=6922 and E188CC=7308.
I used to be as fuzzy in my thinking as most of the tubes you are talking about until recently..nothing like bringing home reference tube gear to compare to exceptional solid state...tubes really do an amazing job at screwing with the signal when used in the pre and main the source however,tube output stages rule!
Dave_b: Please share with us the "pre and main stages" products you used to conclude that "tubes really do an amazing job at screwing with the signal" but that they do not do this at the source. And what source component do tube output stages rule? ..... a tube DAC? ... and which model? And what was the exceptional solid state gear used as the reference? Specifics rather than generalities are always more valuable to the reader.
Two E88CC tubes from different manufacturers will be more alike than an E88CC to an ECC88 or an E188CC
Fantastic! This is where I would like to begin. I've just ordered Glass Audios 1997 back issues per Rchau's recommendation (thanks again!) and hopefully this will narrow the field even further. I would like to hear what an E188CC Telefunken sounds like and perhaps a Siemens CCa as well as the Amperex 7308. Can you recommend specific manufacturing plants as producing higher quality product? I know that the general consensus is that older (late 50s early 60s) tubes were manufactured with more care.

Convential wisdom used to be that Telefunkens had great liquid, detailed mids and highs, but soft bass. Siemens were very linear and had good response top to bottom but were a bit cold and perhaps dry and that Mullards were approached the best qualities of each. I have found this to be the case with different equipment over the years, but admittedly I have not used premium quality tubes till the Valvos. I'd love to own Telefunkens with great bass! I'm also very curious as to how the premium Amperex sound, as I liked what I heard briefly in the Orange Globes that I have.
Look for Siemens & Halske CCa made in the early 60s, identifiable by their grey mica supports versus shiny metal supports. Siemens & Rohre CCa were manufactured later.

The best Amperex and Phillips tubes were made in the Herleen, Holland factory. I have never owned any from the late 50s, but all the tubes I have owned from these brands made during the 60s have sounded essentially the same (given the same brand and tube type).

I prefer Mullards made in the Blackburn, UK plant. They have a slightly warmer and more refined sound than their Mitcham, UK counterparts, which in my opinion sound closer to Amperex or Phillips tubes. Can't explain why this is so, but for me it just is.
tubes really do an amazing job at screwing with the signal when used in the pre and main stages

I would tend to agree with Dave b that tubes are doing something to the signal but then again, who cares? They sound so good and impart an almost indescribable life to the sound. Stop and listen right now to the ambient sounds around you, are they liquid or tube like? Not to me. There is an almost gray or white background and no warmth whatsoever. There is an immediacy and potential for power delivery so ineffable that it cannot be described. There is no place from which to take a point of view. There is no place to hide.

In many ways amplifiers like the Plinius SA-100 Mk III do a good job at approaching reality and the best, almost uncanny experience I have ever had with recorded sound was hearing the Weavers at Carnegie Hall through SAE separates. SAE is IMO the prototypical solid state sounding amplifier. I've heard this recording through many other systems and nothing even came close. Curiosly the recording was made with tubes, so maybe there is something to tubes at the source.

Thanks Tvad! You are really bringing things into focus. Still, I'm a bit confused about the Amperex PQ deal. Is PQ comparable to a 7308 or do they have 7308s that are not PQ? Where do you reach diminishing returns?
Anacrusis, the issue of tubes is not only about tonality. Sit at a piano and hit a few keys. Do the notes abruptly truncate or do they gradually decay? Then listen to piano music through your favorite ss and tube phono stage, line stage and amplifier...even DAC. My listening observations over the years indicates that the ss devices do more to screw up the signal in this regard than do the tubes. The ss devices simply destroy the fundamental characteristics of the piano. Repeat this process with saxaphone and vocal music. The results are the same.
To my knowledge, there is no 7308 that is not PQ.

Here is some required reading about 6DJ8 tubes from Brent Jesse Tubes.

Anacrusis, I say this with intended positive reinforcement and encouragement. It would be beneficial for you to do some additional research and reading about the 6DJ8 tube family. Each 6DJ8 variant has well published differences…leading to the path of scientific quantification you desire. Joe’s Tube Lore takes these differences into consideration. Once you have a little better understanding of the design differences and goals of the 6DJ8, 6822 and 7308 tubes, then take another read through Joe’s descriptions and try to correlate his observations to similarly designed tubes. I believe you might see more germane and less haphazard information in his descriptions than you originally thought.

When you ask about diminishing returns, what criteria are you using? Tube life? Tube quality, i.e. consistency from tube to tube? Their ruggedness and performance in radio and radar applications for which they were originally designed? Or, are you discussing high end audio application? Because if you are discussing audiophile application, then it comes down to personal preference. Many people prefer 6DJ8 tubes to 7308 tubes despite the higher quality production tolerances of the 7308. Others prefer something else again, which is why I have debated that the viability of your quest for a quantified, one-tube-only-for-a-given-circuit is unrealistic as it applies to high end audio.
Jafox, I agree with you even when listening to Glenn Gould:) These are some of the reasons that, personally, I prefer tubes.

I think that perhaps the attack of ss is more realistic only in that it is more immediate. Tubes are definitely more realistic in they allow transients to decay. This is why I have always held the belief that tubes are ideal compliments to electrostatics or ribbons. Where tubes may lack in attack stats excel. Where tubes may lack in bass definition, stats excel. Of course these are generalizations but the idea is there.

One of the reasons I'm so impressed with the Valvo E188CCs that I'm using in my DK is that after 25 years of electrostatics, I have purchased some dynamic speakers with transmission line bass. The Valvos seem to have this unlimited current delivery and have such great structure and definition at the bottom end. Like a great Class A (constant current) ss amp. The sound from top to bottom is marvelous. But even then, I'll be purchasing a tube integrated soon and when I can afford them a pair of Quad 989s as a system for my den, so there you go.

By the way, I think this is the tube:
Specifics are absolutely necessary..I'm sorry for not mentioning my current rig (one of very many over the years, tubes and ss). Mcintosh MC501's with C46 and MF A5 CD player with mu-vista tube output stage. Cabling is all MIT Magnum M1 stuff. Speakers are Dynaudio C4's. Just thought it was interesting that the sound I'm getting is a nice balance between the best attributes of both ss and tubes!!
Tvad, I truly appreciate your comments and I like the way you put it. There is quite a bit of information to digest and I will take your advice to heart.

I have a Musical Concepts Chameleon preamp (Elite) with a PC-1T board which uses a single tube. I am currently using an unknown 6922.

I also have a Musical Design T100 (Ultra) amplifier which uses 2 6DJ8 type tubes. The amplifier came with 6n1P tubes and I have recently tried 6H6p (AKA 6n6p) tubes.

I have found the 6h6p to provide better controlled bass (deeper, cleaner, and tighter), as well as better soundstage depth with more air around voices and instruments in the mid and upper frequencies.

The preamp and power amp I have are outstanding. Truly excellent products, excellent value, and the designer/owner, John Hillig is outstanding to work with. A real breath of fresh air.

I would be willing to give some 6dj8 tubes a roll and report back on my findings.

Let me know if I can be of assistance with your experiment.