I very rarely go on Audiogon these days and even less frequently look at Audiogon threads, but this one came up last night in a google search when I was looking for something else and I read it through.
I know that this will not be news to most of you, but it bears repeating that current 300B tube production is artisanal in nature, as is manufacturing of the single-ended tube amps that most people use 300B’s in - with great respect to their manufacturers, many of whom make incredible products, I want to emphasize that these things are not made by companies like Boston Scientific or Siemens in roboticized factories to critical-application tolerances - they are basically made by hand, one tube can sound materially different than a presumably identical tube from the same production run (not to mention tubes from different production runs), and two identical tube amps from the same manufacturer can likewise sound different, particularly if they are point-to-point wired like the very good ones often are. Just as with Mason & Hamlin's, Fazioli’s, etc., no two sound exactly alike.
So that said, and factoring in how different partnering electronics, home electrical supplies, listening rooms, set-up skills and the auditory capacities of listeners can affect perceived sound, I am wary when someone writes in a thread that one really fine tube is better than another really fine tube. I don’t believe that anyone has done that here and I think it is a useful exercise for owners of a common tube amp (the Coincident Frankenstein here) to report their experiences, but I think it is correct to say that Takatsuki, Elrog, Emission Labs and EAT, and even the high-end Shuguang and TJ / Full Music / Sophias, are all really fine sounding tubes and can all outshine each other in a synergistic amp.
In addition, because some amps run output tubes a lot harder than others, build quality can be a factor equally as important as sound quality. For example, the VAC Renaissance push-pull amps run 300B’s hard, and many feel that best tube life is achieved with VAC’s rebranded Shuguang 300B’s, which have been very carefully culled to withstand the stresses that tubes in that circuit are going to see - they can last many thousands of hours. PS - Any 300B used in Renaissance amps MUST be standard Western Electric-spec 300B’s (BLX tubes draw too much filament current and will cause amp failure, and mesh plates are too delicate and generally fail). So, and I think this is borne out by user reports in this thread, not all 300B’s are going to provide acceptable life in all amps.
I would query the manufacturer of your amp for tube suggestions (i.e., "What sounds good and what’s going to hold up?") as well as a reliable tube vendor (there aren’t many, alas) who demonstrates experience with your amp if you know one, buy three good candidates, put at least 200-300 hours on each tube to ensure they are properly burned in, choose what sounds best to you, and keep as spares the runners up. After another five hundred hours or so, pull them out and do the exercise again - equipment takes time and requires perspective to properly evaluate. Then retain as spares and/or sell the runners up.
Make no mistake, tube selection is crucial - they are the circuit in the equipment they serve and are generally far more important to sound quality than whether you own the "Mark III" or "Mark IV" version of your amp. Investigate what experts (the manufacturer, tube vendors) recommend, spend the money and time to audition good candidates, and never forget that your tubes and your amps are just like your friends and family members - they all have their own personalities, strengths and weaknesses, which for better and for worse, you are just going to have to discover.
