I changed a Tube and…

It makes sense for manufacturers to put cheap and available tubes into the gear they market.  The tubes they offer must be common and easily replaceable.  Because not everyone's taste and system characteristics are the same, there is no clear consensus on what constitutes and upgrade, so why should a manufacturer spend extra on fancy tubes that may make the sound "worse" to certain buyers?  This does leave it up to the customer to experiment and hunt for "better" tubes.  A local dealer in my area carries a wide array of vintage and new tubes and customers frequently borrow tubes to try in their gear to find what sounds best.  This dealer offers recommendations based on what the customer says he wants to change about the sound and discourages obsessive tube rolling (this damages tube sockets), but he knows that some swapping and matching may be needed by his customers.

@thecarpathian 

My understanding is that different shaped getters were used to guide/control where the barium patches ended up. I've always though of them like a wine glass that's designed for specific type of wine to maximize how that particular wine hits your nose and tongue; e.g.. like how a Bordeaux glass differs from a Burgundy glass.

They are also indicative of a date of manufacture. But after the vacuum is created during the production process, they really serve no purpose. I have tubes with huge foil getters that broke off at the post were it meets the mica and it rattles around in there like a maraca. They work fine, like more prone to issues down the road, but a tube with a broken getter is far from a horse with a broken leg.

@larryi 

But this starts with the false, outdated presumption that each specific model of whatever piece of gear must have the same tube as every other piece of gear with the same model number. In the age of co-creation where you get to pick the kind of wood you want your amp built with there is no reason you cannot specify also an NOS tube that is to your taste. The manufacturers that embrace this instead of fighting it I think will be better for it.

@noromance 

Let's talk more about tubes we like. I expect we have a lot of overlap.

I also like the Siemens 3-Mica E83CC short plates. I had a quad or two of some long plates that were nice but didn't do much for me.

I very much like the Siemens mC3 and mC5. The mC6 is a bit lush for me. And the mC1 can feel a bit too airy, but has moments of brilliance. 

My two favorite 12AX7 are hands down the Valvo mCn/mCp tubes and the second one isn't even a 12AX7 - it's the GEC A2900.

I don't run 12AX7 much these days, I favor octal tubes with adapters for the most part. The GEC/Osram/Marconi B36 is one of the best values in audio tubes, period.

I just sold my entire system and am rebuilding it around a VAC 200iq that shall soon be two VAC 200iq's. I am currently experiencing the unique torture that is picking new speakers, preamp, and DAC.

The only thing i can tell anybody about "new" Telefunken tubes is that there is no such thing, unless you are referring to Ei tubes, which is 2/3 of a thing.