The old, original Svetlanas, made in St. Petersburg, Russia, have been out of production for several years. The originals are now going for $50+ apiece as NOS tubes. New Sensor somehow acquired the Svetlana name and is making knock-offs of those and also Mullard, Tung-Sol, et. al.
I have two quad sets installed in amps. One set is the original winged =C= marked tubes with welded plates. The other set is the New Sensor knock-offs, with crimped plates. (I can't tell any difference in performance.) I'm thinking of pulling the Winged Cs, replacing them with knockoffs, and saving the Cs as an investment.
Any opinions?