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

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.

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.

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

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.

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!