Why sound quality on Mac is horrible?

[jayR]

I use both Windows and Mac Mini versions of VLC. Playing the same songs using the same DAC and headphones, I found sound quality on Mac is horrible. It's muddy and blurred. I set the MIDI media options to the same sampling frequencies as my songs' frequencies. there isn't much I can do more. But sound quality is horrible. Is this an issue of Mac's CoreAudio?