The difference between cheap and expensive headphone is its impedance (ohm). High impedance (expensive) means if you're straight connect it to a device, the sound will be too low that you need to crank up the volume or use amp which is more expensive.

Using DAC solves this by straight convert the digital signal that it receive from USB into analog (coaxial, audiojack, optical, etc), making your headphone produce the low-mid-high better.
Basically, DAC is the cheap solution for Amp.

This post has been edited by ray148: Oct 11 2021, 12:15 PM