>>127516983
>youtube has the worst audio quality of all streaming options, and by some margin
download some flac files of cleanly and well-recorded music (ie dont use lo-fi hardcore garage punk etc) that you know pretty well, or play or rip a cd if you can, then you know exactly what youve got. listen to a track for a minute or so, then play the same thing on youtube, then go back to your lossless file or cd, then back to youtube. try to have them both at the same volume and give it a decent amount of time so you get used to what its sounding like before switching. you might want to try a few different tracks of pieces of music
listen for a sense of realism, and a sense of space around the instruments. pay particular attention to vocals, the timbre of acoustic instruments, and most especially cymbals. cymbals in low bitrates can sound artificial and hissy, like an 80s drum machine that just goes "tssss" to imitate a hi-hat. a well recorded and well reproduced cymbal should sound realistic, metallic and not overly sibilant, you should hear the impact of the stick on the metal and the ringdown as the sound dies away.
if you cant tell the difference, one out of your speakers/headphones/ears is below par. but if its not bothering you, thats fine too.