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!