Also, the mix of the music. I’ve been playing with some obsolete formats recently (MiniDisc and turntables), and I’m convinced there aren’t too many factors that affect sound quality. There’s the pickup mechanism (only relevant on analog), quality of manufacture of media (again, only relevant on analog, digital will play anything as long as it’s in spec), bandwidth (increased tape speed, disc speed, bitrate), build issues that adversely impact bandwidth (poor encoders in the digital space, low quality DC motors in tape, records), speaker quality, and the original mastering of the mix.
Actually, I’m somewhat convinced that the limitation in my own audio setups is mostly either the speakers I use or me. I have a HomePod, AirPods Pro, first gen AirPods, and the earphones that came with my MiniDisc player. I’m going to do some tests with a new record I bought, compare that to the same record on Apple Music, doing some tests with Hi-MD MiniDisc. I plan on doing an AB test with 1) record recorded to MiniDisc with a modern digital sampler connected optically to my MiniDisc player recording in PCM, with the same setup and sampler recording Apple Music, 2) Apple Music to PCM with the modern sampler and with the MiniDisc recorder’s 17 year old sampler, and 3) Apple Music using the built-in sampler to PCM, Hi-SP, and Hi-LP. If I had optical on my laptop, I’d test whether Sony’s SoundStage software introduces any issues, and I’d check speaker quality with some better speakers. My hypothesis is that, with the three tests, I might notice a difference on Hi-LP, but probably none of the others.