This is the kind of discussions that reminds me it was smart to ditch my tube preamp and go back to SS. There are already so many ways to tinker with sound through equipment, accessories and room treatments that I felt the added tube complexity was an unnecessary burden. Not trying to demean the tube sound or trying to talk anyone out of it, just sharing my own experience.
Tubes, cheese, wine and cognac
Perhaps, similar questions have been earlier be posted.
I cannot explain why old made tubes should sound better, do they really sound better than new made ones? Or are tubes similar to wine and cheese and need time to get better?
What kind of tools or knowledge was available in 50s, 60s and 70s that is not available?
(Can Egyptian pyramids be built now?)
I didn't try any NOS old made EL-34 tubes in my amp. So far, tried five different new made tubes , including Mullard, Gold Lion and Tang Sol Russian replicas. None of them have more than 10 hours or so. So far, Tang Sols are the best , Gold Lions, which were considerably more expensive are notably worse, Mullards sound the worst in my system. I didn't try Psvane yet, perhaps i will do that in near future. There are a few Chinese reissues, including UK El34 and El 34ph, the latter ones are twice more expensive. They put the tubes in nice boxes like chocolates and sell them more expensive.
But would NOS tubes sound much better?