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: http://www.enjoythemusic.com/magazine/equipment/0304/6sn7.htm

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.
anacrusis
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.
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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 stages...at 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.