FiiO D5 Coaxial/USB Decoder DAC & Headphone Amplifier. FiiO's D5 is an advanced multifunction USB audio interface. When connected to a computer, it works both as a high quality external sound card (DAC) and a dual microphone input interface. It is therefore ideal for enjoyment of high fidelity audio playback, making voice recordings, and usage with network voice applications.The FiiO D5 Coaxial/USB Decoder connects to a computer via a USB connector, and functions as both, an external sound card, as well as a dual microphone input interface. It is suitable for high fidelity audio playback, voice recordings and network voice applications. The D5 Decoder features a coaxial output that provides output stereo PCM digital audio, and can be connected to coaxial audio devices. In addition, it comes with a 3.5 mm output for connecting your headphones.With the stereo line out, the D5 can be directly connected to an amplifier or speaker. Moreover, the line out is automatically muted once headphones are connected. The decoder draws power via the USB connector itself and hence does not need any external power cabling.