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

Hey anacrusis, give up your quest for accurate infor on a specific model of tube characterists.
I've tried and have had little luck. You raise a very good question that everyone wants to wiggle out of.
I personally do not go cahsing after a "magical tube". Obviously I leave that decision up to the designer of the amp. If i get the amp and it fails to deliver what i need in my muisic, away she goes.
On the tech topic i asked what are the general characterists of the following tubes 6550, Kt88, KT90, EL34.
Received one good answer, Others were vague and elusive. not straightup.
You are right , by replacing a few tiny pre tubes, you may give up one slight characterist in one, for another. But almost always too subtle a change to notice.
I thought about rolling the 4 russian 6922's in my Cayin 17 cdp, but guess what, I'm not. The designer put them in and thats where they'll stay.
If i get a tube amp, and don't like the sound, i'm not going to "roll" the tubes to get better sound. To me thats nonsense.
Just dump the amp and get one you like better.
its that simple.
What a silly game "tube rolling".

My tube rolling experiences with many tubed-based components is polar opposite to the comments made by Bartokfan. What exactly are people trying to wiggle out of? Quantifying how each and every brand/model tube will sound in each and every component? Sorry, but as Albert already alluded to, it's just not that easy.

In some cases, the differences can be subtle. And in others not at all. There have been times where a single pair of tubes changed in a component resulted in greater refinements than I had achieved in past component upgrades that costed far more. If all you hear time and time again is a subtle change, that indicates the limitations of the component or system under evaluation and not the process of comparing tubes.

From what I have learned with trying various Mullards, Telefunkens, Brimars, etc., EL34, 12ax7 and 6922/6DJ8 tubes, I would never make final judgement on any component that contained Sovtek tubes. These things are mediocre at best. No master audio engineer can resolve this with fancy capacitors, point-to-point wiring, teflon boards, chassis dampening, 18 stages of regulation, etc.

As for what tubes the designer puts in a new product, obviously new off-the-shelf tubes are the only option due to availability and guarantee issues. But with very little effort, many of us hear components perform at levels even their designers never heard.

Bartokfan, you are free to keep the stock tubes in your preamp all you want. And this is good news to the rest of us as there is one less person to compete with when a good deal on older tubes becomes available. But do not condemn the efforts and experiences of others who have significantly different results than yours. And to claim it is nonsense clearly indicates you have a lot less experience with this process than a number of Audiogon members whose reports in these forums echo mine to a T. Afterall, you are into component rolling while the rest of us do it at the tube level.

What I find silly is to go through preamp after preamp, amp after amp, etc., the cost of shipping and potential for damage, until I find a stock unit that meets my goal. Sorry Bartokfan, but it is not that simple...it is naive. I'd rather purchase a few pairs of tubes that cost me $10 or $20 to ship, try them in my system, keep the ones I like and put the rest back on the used market. Now that's simple. It sure beats packing and shipping 50-100 lb components around the globe.

Through the sharing of tube-rolling knowledge by others with the same components as mine, I have taken my system to a performance level that I never knew possible with these components. Rather than put a negative spin on this and call it a silly game, I think of this as a continued quest for refined magic.

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.