In my experience with EL-34's, the Svetlana's outperform both the Sovtek's and the Tesla's (I have not tried the E-H branded Sovtek's). In my c-j amp, the Svetlana's have the smoothest and most extended response at both ends of the spectrum, possess the more finely developed midrange, and give the best bass firmness. They also have the least "electronic"-sounding artifacts. I would rank the Tesla's number two sonically, but they have been less durable than either of the Russian brands.
