That was my first take too, but when I read @nhatlam96’s post again, I don’t think he’s saying that. I
think he’s saying that if you listen to 2 amps that have the same sonic signature, there’s a danger that bias and volume mismatches might make us believe that they sound different.
I think those are valid points, having just finished a 4 amp comparison that I still need to post (Lyr 3, Asgard 3, Pendant vs a Burson Soloist 3 still in trial period, to see if I want to keep it). There were clear differences between them, but in some cases, they were very similar and I have to admit I did catch myself looking for a difference. Once I realized that’s what I was doing, I had do the test again, challenging myself to see if I really was hearing the difference or it was just wishful thinking. Obviously the repeated test was still subjective and subject to bias.