Unfortunately I’ve not been in the market for one in ages.

What I ended up getting years ago was a FiiO M5. It’s a portable music player, except it can function as a USB DAC, as a BT transmitter or receiver, OR as a player on its own. I don’t think you can get one anymore.

At the cheapest, a USB DAC will just look like a usb adapter cable to a 3.5mm jack, with the electronics hidden in one of the plug ends. Watch out for ones that say they only work with certain phones. These don’t contain a DAC, they are just an adaptor, and actually use the DAC in the phone they are for. That means they are fine for use with that phone, but wont work with anything else.

It looks like FiiO sells the KA1 USB C DAC now. It’s just a little cable, too, but with room for some more serious electronics. Might still be pricier than it has to be, tho.

Honestly, unless you’re getting headphones that require a decent amount of power, you should be good with Apple’s USB C DAC that they sell for around $8. If you have a limited budget, it’s better to put as much towards the actual headphones as possible, you’re going to get a lot better sound out of $100 headphones through a $10 DAC than you would with $50 headphones through a $50 DAC

Digital to Analogue Converter. An audio signal must be converted to analogue in order to be fed to an audio driver, so anything that takes digital audio data and actually plays it, has a DAC somewhere. Your phone has a DAC, your laptop has a DAC…

Headphones that use USB, have a DAC, because USB doesn’t do audio. It only does digital stuff. Hence USB heaphones are actually DAC and heaphone combos. The USB goes to a DAC, which goes to the headphones. Except they are connected together with no way to use either separately from the other.

But you can get USB DACs, little USB stick looking things that plug into a USB port and have a headphone jack on the other end. If you then get any other normal pair of headphones, you can use the USB DAC to use those as if they were USB headphones, whenever you need.