Yes, the DacMagic is compatible with Mac computers. However, you will usually need to tell the Mac to output sound to the DacMagic rather than to its own speakers.
From the Apple menu select system preferences, and then choose sound option from the hardware section.
The DacMagic should be listed as C-Media USB Headphone Set as well as any other sound card devices installed. Ensure that the above device is highlighted to enable the sound to be output via the USB to your DacMagic instead of the built in sound device.
If you wish to temporarily stop using DacMagic and revert to using your computer's internal sound card while leaving all connections in place you may do this by selecting system preferences again from the Apple menu and in the sound option re-select your computer's internal sound card or alternative device.
When you disconnect the USB from your Mac, the sound will revert to the previous device before connection was made to the DacMagic.