I do not 10 as they are not perfect, I find them more fragile than the Sovtek that hold the shock in all circumstances, it hotter, snap a little faster (one of the four I put in place three months and other grilled quickly, obviously). I have therefore remetre Sovtek original crate in my V3112 and I really felt the difference, even though my amp does not turn three with JJ Tesla. Since then, I gave him the JJ Tesla too powerful (graded to 27) and the difference is even more blatant: the Tesla is far more dynamic, have more safe, they cover a wider sound spectrum, the receiver breathing, the solos with a Tube Screamer singing really is more tubby, warmer sound while Sovtek carément cardboard in comparison. More and more of everything really. Well, the downside is that they heat up, even if the amp is cathode bias, choose a grade that matches the receiver (here, not over 29, and 29 already is a lot) they are more fragile than the Sovtek but less than others, but hey, they are not cheap (40 euros quad matched on the net). In short, they have their faults, but they sound great and this is essential. They sound bright enough, so they combine perfectly with JJ Tesla 12AX7 that sounds a bit dark and loose. Sylvania with a reissue, that's fine too, with ground Tung, ibid. They cash in the pedals very well too. Probably one of the best in the recent production EL84. I'll try the tad-GTR who also reputable.