By EQ you are referring to equalizer? So if I don't use EQ on RPi (which I don't), I'm good? Is there some particular audio clip which I can sense the crappiness when listening to?
To hear these sorts of things, listen for reverb tails on drum hits, high frequency percussion like cymbals, high-hats, solo human voice (we're quite good at hearing unnatural artefacts in voices) - that sort of thing. Beware it has to be good quality source material to start with though!