Electro Harmonix valves vs...

The Svetlanas are a little smoother ( IMHO ) in the mids and maybe a bit more bass. Of course it will depend on what your associate equipment is, as to how well you will notice a difference. Check out this website and read what they say about the Svetlana.

http://thetubestore.com/el34review.html

They do not compare it with the EH tubes, but unless I'm mistaken the EH is the cream of the crop from Sovtek. Of coures if I'm wrong I'm sure at least 5 people will let me know before this thread has reached it's end.

It's hard to get a straight story about any differences between Sovtek and E-H branded tubes, but I generally assume they're the same tube with different logos and boxes - after all, they're made on the same line in the same factory, and they look the same when you gaze inside...

In my C-J MV-55, the Svetlanas have been clearly superior, IMHO, to the stock Sovteks C-J supplies: Better extension at both ends, better bass control, fuller midrange, airier highs, cleaner transients and livlier dynamics, with more transparancy and resolution accross the spectrum noticeable primarily as a clearer sense of 3-D space and location, allied to a comparitive lack of "electronic"-sounding artifacts making for a smoother, more natural-sounding presentation overall. In previous posts on this topic however, others have begged to differ (some citing the Tesla/JJ Czech tubes, which placed in between the Sovteks and the Svetlanas in my shootout), so I think it's safe to say that YMMV, and that the particular circuit a tube is used in can make a big difference in which brand is ultimately preferred.

I agree with the Svetlanas being better.Have both prefer Svetlana by far! Thor 30 watt tube monos.

Update: Having very excellent results with Electro-Harmonix KT-88's vs. Svet (SED) 6550C's. And apparently this EH KT-88 is *not* the same tube as the Sovtek version. (I haven't tried either the Sovtek or the SED KT-88's ; nor did I try any 6550's other than the Svet's.) Live and learn...

Update:
Tried EH valves in my VTLs. They have better bass controll but its reliability is totally unaccaptable! Will never ever use them again.
Currently use 6CA7 yugoslavian fat bottles flowlessly with advantages of both: Svets and EH.