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.
