I said: "there are local people who have listened to my system over the years and made suggestions which improved it" and you want to know how that’s happened.
Well, for starters, the Colorado audio community is fairly large. At least 4 have come to my house and helped with comments. Their systems are equal to or better than mine. At least three people on this forum have been to my house, too.
I have several friends who are not audiophiles but are careful listeners. They notice things and can communicate what they hear.
Others are email correspondents from this forum. I described what I heard was going on in my system and they said, "Do you hear this?" or "Try that and then get back to me about what you hear." That process of dialogue lead to insight and discovery.
If you find it "fairly fantastical that one has access to that kind of expertise" all I can say is that you might need new ways of describing what you’re hearing to new people who are, respectfully, more perspicuous and articulate than the people you typically interact with.


