Howdy guys! I do have a tidbit or two on the Svetlana name. You may have noticed there are two Svetlana logos in use, the original "S" logo, and the newer "Flying C" or "Winged C" logo. The "C" is the Cyrillic character that corresponds to the first letter of Svetlana when written in Russian, so I'm told.
In 2003 I believe, New Sensor, owner of the Electro-Harmonix and Sovtek brand names, bought the Svetlana name brand. An legal dispute forced Svetlana to abandon use of it's "S" trademark and Svetlana brand name, which are now used by New Sensor. Svetlana changed it's name to Svetlana Electron Devices, and it's tubes are now sold under the SED brand name and "Winged C" logo. The tubes are still made in the same St.Petersburg, Russia plant, and are still the same high quality.
Today, New Sensor makes tubes with the Svetlana brand name and "S" logo in the Saratov, Russia plant, which is where the tubes branded Sovtek and Electro-Harmonix are also made. The new "S" logo Svetlana is not affiliated with SED in any way, and their tubes are inferior compared to St.Petersburg Svetlana production, either past genuine Svetlana "S" or present SED "Winged C."
For those who may own Decware Zens, the Svetlana "S" SV83s that are available are all NOS genuine Svetlana, as this tube is out of production. Ditto for EF86s and some of the newer Svetlana power triodes such as the SV572.
When it comes to types such as EL34s, 6L6GCs, 6550s, and other types that are currently made in both facilities, make sure they have the "Winged C" logo to ensure you're getting the real McCoy.
Thermionic