dac/ amp sound much more different than opamp rolling. Even changing a resistor value or low resistance pot will make more difference than opamp rolling. Opamp difference can be overlooked i agree thats why many pro products use jrc4580 and 5532. But the difference caused by different circuits are not.
This was interesting to read from you of all people. I came to similar conclusions aswell, confirmed with blind testing, though the common attitude is still that this is impossible...
My blind testing with op amps cant really be confirmed, there could be circuit issues (though I dont believe it).
Some actually conclusive blind tests were with different DACs and an o2 amp in the past. Mostly ODAC against Topping D50 but also iPhones, Realtek PC output, Soekris R2R. I actually started when I didn't like the sound of ODAC and bought the D50 to test for myself if there was an audible difference or not.
All these devices with low levels of distortion that are considered to be inaudible but all relatively easy to tell apart consistently in blind testing over many trials.
Also worth noting that the differences I thought I heard in long term
sighted listening with these DACs, were the same differences that let me tell them apart in blind testing...
I have a D10S on the way to test against D50 next, the O2 amp will need upgrade too.
Would you (or have you?) consider doing more blind tests and recording results to post on here?
Although it is warranted, seeing people's sighting listening impressions being dismissed as being totally imaginary by people who are probably half deaf or never attempted any tests themselves when you already know it is possible starts to get frustrating after a while .