I've been listening to music for a long time using the cheapest headphones of any type, on all devices until ~2010 when I noticed that on PC the music has more of a stereo feel to it than on tiny mp3 players. Then I bought a pair of ~80 usd headphones (don't remember the brand but the point was it wasn't the cheapest, and it was entry level price) and it sounded a lot better, and I could distinguish new detail which I previously wasn't aware existed in my favorite tracks. If connected to phones or mp3 players though, it also brought out a little bit more detail, but not as much.
Then I bought the cheapest internal Sound Blaster PCI-Express audio card I could find and then I found out there was even more to hear in my favorite tracks. The low frequencies became notably more powerful, but not in the way that blocks out the high frequencies and drowns out all detail, as you'd get if you play around with equalizer software on builtin Realtek AC/HD codecs. Compared to any portable device with a 3.5 jack this is night and day. But why is that exactly?
What electrical characteristics allow the discrete audio card bring out more detail and significantly improve low frequency sounds without losing all detail of higher frequency sounds? What does the cheapest PC audio card have that portable music players and even high end phones don't?
For comparison, Realtek ALC 892, HD and AC'97 all produce inferior sound in my opinion to all of the dedicated audio cards I've listened to.