That kind of money, it's not audiophools that are the end-market; it's probably guitarheads and other professional musicians. In that application, they DO make a difference; they don't make them the same way anymore because hand-fab vs automated. Old-production Amperex 12AX7s are sought after for fuzzboxes AND analog synthesizers. They are ALSO sought after as preamp tubes because their construction does alter the sound in that the low-mid and mid are accentuated, adding "warmth" without the distortion that running through a bandpass filter causes.
I'm curious. How does a (passive) bandfilter add any k2, k3 ... kn distortion to a signal? The "warmth" or "singin' "
as for example in Gary Moore's playing can be heard ("Still got the blues") comes definitly
from the k2 distortion of the tubes, which is very typical for triodes (not so for pentodes).
I don't condone robbing vintage test equipment for these tubes; but CONSTANTLY repeating the mantra that it's ALL in their heads really does make us all sound like the old farts & hobos that we disdain about hamfests.
If it is not in their heads, then you can measure it. If you can't measure it, then it is imho audiophoolery.
I do believe in the laws of physics since they are reliable and repeatable. Not so with this marketing babble
of a big lot of these audiophools.
And I'm staying all the time behind a flat frequency response between 20 and 20kHz and a zero degree phase
between the same frequency band.
All other saying is nuts and foolish. Imho.
Exception: If you want to create an effect like this singin' guitar as in Gary Moore's playing.
But this is a different playground.
If you want people to believe you know better, you need to NOT repeat ignorance like this about EVERY TIME you hear folks raping gear for valves. All it does is reinforce the "What The Fuckever" attitude in those circles.
The ignorance is on their side. They are denying the laws of physics, not us.
And before y'all dogpile me with pages of ridiculous adverts of moronic products featuring these precious artifacts... remember that there are a LOT MORE people selling this shit than there are people buying; literally 90% of the "product" we refer to as audiophool gear is vaporware: It does not even exist UNTIL someone buys one.
And this doesn't make things better in any way.
Just my 2 cents.