electro-harmonix vs svetlana tubes

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.

I have both Svetlana EL34 and Electro-Harmonix EL34EH tubes that I use (not at the same time of course) with my C-J amp. The quality of both are very close and makes the choice one of personal listening preference. I usually like the Svetlana's just a fraction more than the EH because of the full mid-range. It seems that the EH tubes have slightly more gain and more punch in the higher frequencies. I cannot say regarding the longevity of either of these because I have yet to have either set long enough to need replacing. Both companies could work a little harder at reducing the distortion levels as compared to the NOS types.

The performance, and sonics, of both tubes, will depend on the circuit, they are used in. To me, the Svetlana's, sound better, when the circuit is biased, on the high side. The Electro Harmonix, does not seem to like this. As with all tubes, the end sonics, will be influenced by the circuit, bias, and amount of current, that passes through the tube. In one amp, they may be heaven, and hell, in another.