i have write sound bad ?
i write there is mesure here , same place , same material , before and after a change of opamp or condo
if there is change in listing , but not in data its religion
there is science : your brain , and your ear its not the same at 20 and 60 : its impossible / false to says what you hear in 1990 and 2030 is good or bad : not same source , same place , same brain
the proof : you change 100 time material because YOU change
You are vastly over-extrapolating the data from science. If you normally listen to sine waves, then science and data will be more accurate in reflecting what you hear from your system. Music is a gazillion times more complex than sine waves. It's like testing somebody's skill at checkers, and then extrapolating that to conclude they will excellent at 3-dimentional chess because they were good at checkers.
Since you are focused on controlled change, why do you think that performance measured with very simple test signals would be a reflection of how it handles music signals that are orders of mangitude different and more complex than test signals?
Out of hundreds of amps over decades, when you can only remember a small handful that sound bad -- they sound bad. Especially the Adcom, where I spent 6x and had far worse sound -- trust me I wanted it to sound good because it was a stretch for me to buy at the time. If I had bias, wouldn't it be toward the thing that just cost me a fortune? If you search around, you'll find plenty of people that say that (unmodified) Adcom from that era sounds bad -- plenty -- and those Adcoms measured very well. Data has it's purpose and I really appreciate this site as a resource for testing, but it's not a substitue for listening. Checker experts often aren't chess grand masters.