Some pretty bold and amazingly inaccurate statements about tubes in general and some wild claims in specific.
Where the heck does all of this stuff come from? Certainly not from anything remotely engineering oriented, that's for sure.
THIS, is why the tube marketing folks find the market so ripe for easy pickings. So many inaccurate assumptions/statements that are not backed up with fact.
It's one thing to be a hobbyist, who rolls tubes for fun and games and for bragging rights. It's an entirely different thing to have designed and tested many different tube circuit designs and has worked with many tens of thousands of tubes over decades in the industry. These specifically include ageing tests where I have tubes (including Russian and Chinese) that have over 15,000 hours on them in test circuits that I can periodically measure to see which ageing factors can be normalized by careful design. Then we can go back a generation, as tubes are not something new in my life. My dad designed with tubes all through the 50's and 60's, mostly in military and aerospace applications. You don't think that I pick his experienced brain for whatever insights he might be able to contribute? Many of the problems we see with tubes today are not new problems but a continuation of the challenges faced since the beginning of electronics. Wild variations in parameters make comparisons between 2 tubes more about comparisons of a spread of variables than any generality could hope to disclose.
Regarding plate length, one major reason for increasing plate length is to decrease plate current density which can improve linearity in high plate voltage circuits that use a combination of lower value plate resistors and lower load impedance. The problem with this is that capacitance between all of the elements increases, leakage increases, and because the grid and cathode must also be longer the microphonics issue is greater even in a well constructed tube. The Mesa current production 12AX7 tube is not a long plate tube because they just do not sound as good (in the circuits/applications they are used in), nor do they hold up as well.
Regarding less expensive and more expensive tubes, I think you would be shocked to know how many expensive tubes did not start out as expensive tubes but are nothing more than exquisitely marketed versions of the better quality every day tubes. Sometimes they will screen them for a set of parameters that support the marketing, sometimes they screen discards (or returns) to find unusual outliers of one parameter or another (I once had to screen returns because I needed a specifically "defective" tube for a very unusual and unique circuit, this parameter made the tube unusable for other applications so in this case it worked in my favor, and this specific product alone probably consumed 10k tubes, with a predicted lifespan (because of the way it was used) of well over 20k hours.
For those of you who want to believe, by all means enjoy what you are doing. Nobody is going to lose an eye over this. Those of you who are maybe a little more skeptical about tubes, good for you. Use your ears and some common sense to prove to yourself that you are indeed getting what you think you are paying for and not getting hustled. I don't have a dog in the resale tube race, but I get enough PM's and e-mails with serious questions about tubes and wild claims that I feel it's good to get some of this stuff out in the open for the sake of honesty.
