OK, it seems that I have got circa 300 hours of burn in on those tubes, I might write some summary of impressions about those tubes.
Burn in. Tubes change dramatically during 50 hours, after that I was seening little or unidentifiable changes. Those tube take 300 hours I believe to burn in completely, before sounds settles up completely. There is one interesting thing to mention - the base came up suddenly after 100 or 200 hours (cannot tell), it becomes solid and punchy and articulated, just out of blue.
I think burn in is important, since the sound becomes definitive, airy on highs and seem to improve sound just in every direction.
Out of the box. Sound is wonderful, by all means. Easily beats up Golden Dragons and Svetlana which I used before.
Qualities of the sound.
Soundstage. It is big, huge as compared to those tubes I used. Soundstage seem to increase in wideness as well as in deepness of the scene.
Midrange. Sound very open, without any veil, very lively.
Bass. Punchy, articulated, but gets even better after 100 (200) hours. It is not boomy by all means.
Highs. I think the most difficult part in the sound of those tubes. I found myself wondering where are the highs?? :). Having compared to Senn Hd650 (Stefan Art audio cable), plugged in Zana Deux micro (Russian variant of famous headphone amp) I realized that they just give what I have in the system (I use Audion Phono, Pre-Amp and Silver Night classic SET 300B) running Klipsch Heresies 3. Very revealing the quality of recordings too - switching between vinyl and CDP, easily seening how the record was made.
Starting from this, I changed wiring in amps (all three) to silver (audio consulting wires). The effect was immediate - more resolution came up right away.
Sound texture and resolution. I think they give very good level of texture, could notice subtle details in performances.
Way of presentation. The most magical part of the tubes. It is so addictive that you could find yourself wondering about CD/LP music (not sound!) sounding sooo gooood... Starting listed to LP I often stopped when the side has been played through. CD - listening track after track. The best word I believe would be seductive (tubes). The sound is so easy and relaxed that often at times I fall asleep :)
Now, what about drawbacks?
1) They are most expensive tubes in the range (twice more than TJ Full Music Mesh plate)
2) At my system, I would not say the imaging was very exactly locating instruments and performers.. But that could be my system, may be horns are not good at that, compared to bookshelf speakers.
3) They are quite revealing, could be thought as drawback by some people, I think, in some systems.
4) It takes 300 hours to burn in !!!! you could go nuts before they settle down.
The final part of the impressions would be when I visit a friend (he has WE new production and 2 amps using 300 B) to make a comparision like A/B to see how they perform vs. westerns.
