In my little bit of research into tubular options, I've noticed several different "brands" or "labels" of the same type (KT88/6550 in my case) of tube all made in the same Xpo-Pul factory (Reflektor) out of Saratov, Russia. These include: Electro Harmonix, Sovtek, Tung Sol, Svetlana, and the Gold Lion reissue. Now, I've read many different reviews on these, and looked at the cost differences, and have to ask: What and how are the differences between these tubes as it relates to them coming out of the same factory? How could one tube type out of the same factory have so many different characteristics? Is it an inconsistency within the factory, as it specs tubes? So say Sovtek accepts a spec'd tube within so 'n so, and a $$ Gold Lion is spec'd here? Or, perhaps they run in batches, the different "brands"? Anybody enlighten me on the subject, I find it a bit interesting!