Oh, definitely, faith is the operating word here. On many an occasion highly trained audiophiles were able to detect “day and night” differences not only where the could not be any (cables, fuses, cable lifters etc.) but even when the “A” and “B” systems very identical! Not that it were limited to audiophiles of course. In a well-known experiment people were raving about a wine in a glass they were told was poured from a very expensive bottle, and had all kinds of nasty thing to say about the glass with “three buck Chuck.” Wine was, of course, the same.
Ironically, when it comes to telling a difference that does exist, like MP3 and a high-res file, there our golden ears tend to fail quite pathetically (but then you pretty much have to be under 30 to hear it reliably).
As for differences in individual hearing (not taste!) of course they exist, but within reasonable limits. No matter how many times the Chord guys claims to hear well below the brownian motion noise ,and not to need any stinking blind tests, it’s still utter bull. Unless, of course, he is not actually huiman. At least that would explain the design of Chord products.