The Winged =C= (SED) Svetlana plant made some very reliable power tubes. I hated to see the company fold, when their plant burned down. Comparing them to my NOS GE and Sylvania 6550 iterations; their presentation was quite acceptable. Used a couple octets, from Upscale, myself. Now, unfortunately; most of what’s left are factory seconds. As for me, if there’s a new sweetheart on the block; it’s the GL KT88, Russki repop. They yield most of what I got from the NOS valves, in sound, and (over the past couple years) have displayed no reliability issues.