Yet you might want this to be true.. we all want the worth of the money spendBy the way, I am of the Bruce Rozenblit school of audio. I don't expect that most passive components manufactured to reasonable standards of competence have any sonic bearing on sound quality. No special cables, no special volume controls, no "audio" caps, etc. etc., etc.
"And recently when I did an op amp switch on an amp - again adjusting relative volume by ear - I could easily hear the difference"