Hearing differences between amplifiers isn't like alien abduction. The latter is attested to be a hand full of cranks; the former by hundreds of thousands of audiophiles worldwide.
I'm not anti-science. Good scientists know that all science is subject to revision. It's not us audiophiles who are the dogmatists, it's the-all-amps-sound-alike who are the dogmatists. (It seems to me it's the engineers who believe that science, their branch at least, is cast in stone).
I come to ASR because I believe that the differing measurements between, say, a Benchmark and a typical AVR are important to the sound. It's hard to understand why they would matter to an all amps sound the same dogmatist.
No one here has ever claimed “all amps sound the same,” that is a strawman argument.
What many people here, I would wager, suggest is that the bulk of differences that audiophiles perceive between amps are due to psychological bias, not objective differences in sound.
I suspect many people still cling to the idea that their perceptions of differences in sound between amps are based in real differences in audio performance because they have never even attempted a blind listening test with even a modicum of rigor.
But a substantial number of people
have attempted such careful double blind listening comparisons and failed, including people like John Atkinson of Stereophile who have heard the “obvious” differences in sound between amps evaporate in a proper blind A/B comparison.
What’s incredible to me is that Atkinson apparently still thinks there are audible differences in amps that can’t be picked up in AB testing that manifest in long-term listening. This is a testament to how convincing the effects on listening perception psychological bias cause.
To argue that there are perceptible differences between amps that don’t show up in ABX testing is an extraordinary claim and I’m not aware of any evidence to back it up.
I highly doubt you would be able to distinguish between a Benchmark AHB2 and a comparably powerful AVR in the way you might suspect.
Benchmark makes a bit of a todo about a careful ABX comparison between their amp and a respected competitors amp that was conducted at a low power level. (.01 watt).
But this test was conducted with a sinewave. The audible threshold of distortion is much higher on a steady state tone. The fact that they do not tout a similar feat with real world audio sources (music, voice, movies) leads me to infer that they were not successful with such a test. Mainly because a result would be very notable in the objectivist audiophile world.
https://benchmarkmedia.com/blogs/application_notes/power-amplifiers-the-importance-of-the-first-watt