My perception changes over time. I think I hear distortion that I hadn’t noticed before, or some detail is all at once smeared in a certain frequency range. I can check on my headphones, which are an entirely different system, to see if it’s just me or if I’m really picking up on a problem. 99% of the time it’s me. I hear the same problem on the headphones, or anything else I listen to. Sometimes things actually seem to sound very different. Other times they sound the same, but for some reason aren’t able to have a positive effect on me like they do when I’m in a good mood. What’s weird though is that usually when I’m not enjoying the sound quality much at all, I can still really get in to the musical styles and lyrics. So I keep listening, but purely as a music lover, not an audiophile. Most of the time I’m both.
Another perception I’ve noticed is that I’ll listen to a song for the first time, and be astounded by the sound quality, with a strong recollection of how certain things sounded amazing. Further listening to the same tracks I hear them different from then on, and it doesn’t seem as amazing. But the memory of it sounding amazing persists, and creates a sort of mythical place in my mind of that one special moment, lost somewhere in time and space.