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
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.

http://www.tube-classics.de/TC/Tubes/AudioTubes.htm
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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.

http://spazioinwind.libero.it/themagicsound/_private/le_valv_telefunken_eng.htm

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.

http://www.wiwitubes.com/pic/tube/TFKecc88.jpg

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.

John

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!)