I do think some poeple are finding out that you can increase the performance/and longevity of a modern day tube by having it cryo treated.This will bring the so called cheap tube much closer to the NOS tube. Companies like Tube world sell cry'od tube and people are buying like crazy. Some tubes seem to do better with this treament than others. I have bought cables from a company call Ridge Street Audio that will send out your tubes ( at a fee of coarse ) to have them cryo treated and send them to you. I am using Svetlana EL34 and 12ax7s that I will eventually do just that.
NOS tubes, why can't modern tubes sound better?
Perhaps this is a useless thread, but why can't currently manufactured tubes at least equal the sound quality of NOS? With the advances in science, why is it that a modern factory cannot exceed the sound quality of the past? Perhaps for the same unexplained reasons that modern violin manufacturers cannot attain the 'Strats'.