I don't doubt that you feel the difference between the two - but that doesn't mean there is a difference.

Without a double-blind test, it's just conjecture. Audio is notoriously subjective, and existing research shows that 320kbps audio is indistinguishable from lossless.

And to be clear, this isn't an accusation that you're necessarily imagining differences in sound. It could even be something as simple as one source being very slightly quieter than the other (due to the player software rather than differences in the audio encoding).

A good test I typically use is this ABX test:

https://abx.digitalfeed.net/

> I'm no audiophile, but even when downloading the highest quality files and playing them locally Spotify is still noticeably worse quality than the default AAC files that Apple Music downloads for me on my purchased music.

That's simply impossible, the Spotify client does not change your local files, it simply plays through your OS audio stack. You are noticing the difference in loudness, you can't know if the files you downloaded have been mastered the same way than the ones Apple Music is playing.

I just tried with some of my own music, played the exactly same file as a WAV rendered from my DAW and then a very high bitrate export through the Spotify client as a local file, there's absolutely no difference.

Did you confirm this with blind testing?

Often it’s also just loudness/dynamic range compression.

Yeah you'd need to level match a couple of tracks, then blind test between them. Or else turn off normalisation.

Agreed. I release my own music on everything except Spotify as they do something horrible to them (and they're pretty awful people too).

Audio compression is based on psychoacoustic methods. Perhaps it's not your ears but different wiring in your brain that makes you capable of telling the difference.

That may be the case. I believe if you've listened to a track long enough, some of the minor details that lossy encoding remove are remembered and if you're listening closely enough, you notice their absence. My most recent experience was a particular moment in a song. I was listening to the lossy encoded version and it sounded weird to me. I grabbed the original file and that's when I noticed the difference. I believe someone else would have not noticed, but I've been listening to the lossless version and perhaps my brain has a vivid memory of that section. I don't notice when I'm playing with cheaper headphones and speakers.