They are DAC/amps. External sound cards. Crazy guys (like me) use them to: 1) Override the built in sound card in Macs/PCs 2) Override the sound chips in smart phones Basically, the PC or smartphone is just a "tupperware" for your songs, the ingredients. With everything connected, when you press play on the e.g. phone screen, the ingredients get transported to the Mojo/Cozoy, and the Mojo/Cozoy cooks and serves them to your ears. Your phone doesn't do the cooking. There are various players in the market. I'm at work now so I can't really Google them down for ya. Soo...freaking...many. FiiO, iBasso, Sony, crikey. See what your ears like, try them out. When in doubt, trust your own ears, meng. No matter what the reviews say, at the end of the day, only your own ears will tell you what you like. Godspeed, and happy listening/hunting.