The more reputable dealers will go through the same rigorous process of testing for noise and matching tubes. So no issue from buying from tube dealers. "Third-party" is probably not the right word to describe these dealers. They get the tubes from the same source as all the audio manufacturers. And you pay less, actually, then what the manufacturer will charge you, in most cases.
Regarding NOS tubes, it's more like "they don't make them like they used to" The golden age of tube was back in the 1950s and 1960s before transistor was introduced to the world. Now adays, it's just a small nich market, and all the art and know-hows have been lost. And the tooling too.
We just replaced a pair Sovtek 6922s in my friend's Sonic Frontier Line 3 with a pair of NOS tubes (Amperex 7308 USN-CEP white label) last month. And all four judges had their jaws dropped to the ground. One guy hasn't stopped talking about trying to locate a pair since.
FrankC
Regarding NOS tubes, it's more like "they don't make them like they used to" The golden age of tube was back in the 1950s and 1960s before transistor was introduced to the world. Now adays, it's just a small nich market, and all the art and know-hows have been lost. And the tooling too.
We just replaced a pair Sovtek 6922s in my friend's Sonic Frontier Line 3 with a pair of NOS tubes (Amperex 7308 USN-CEP white label) last month. And all four judges had their jaws dropped to the ground. One guy hasn't stopped talking about trying to locate a pair since.
FrankC