New production 12AX7

[überfuzz]

I guess it can come down to how many db you consider relevant (or irrelevant).
[ATTACH=CONFIG]33255[/ATTACH]

That graph comes from the following article. Some of the contents are debatable, but I don't have a problem with that graph.
https://www.amplifiedparts.com/tech_...ent_made_tubes

km6xz is right in his response to this graph if the bandwidth is considered, but not quite right when it comes to tubes in audio equipment. Try altering a eq setting by 3dB at some frequency and hear for your self. So, if we hear a slight change in tone when we replace tubes it's most likely because there is a slight change in tone. Even so a tube might be in specification when it comes to bandwidth.

[g1]

For tubes with differences like that to sound exactly the same in an amp would require that every other part in the circuit have a perfectly flat linear response to both clean and distorted signals.
Otherwise they can not sound identical.

[Leo_Gnardo]

Crappy sounding is 100% subjective and everybody has his own standard, meaning there is no standard.

But :
* whistling
* howling
* hissing
* popping
* ticking
* clanking


are ALL measurable; easily and with precision (and repeatably, I might add).

And your test gear will clearly show the differences.

Don't compare pears to oranges.

Test gear stuck on either side of my head works pretty fast and accurate to weed out the unacceptable ones, no need to prove it with lab tests.

Pears? Oranges? stick 'em in the blender, add some rum, all is good! AH, to your health !

[J M Fahey]

I wonder why I waste so much time here.

Maybe I'm a masochist after all.