The E17 is Fiio’s latest offering in the headphone amplifier arena. What sets this apart from many other headphone amplifiers is its ability to be both a headphone amplifier and a digital to analog converter. What does this mean for you? The E17 can take a signal from a computer via USB, from an optical Toslink cable, or from a digital coaxial cable. Essentially this is a portable sound card and headphone amplifier – that’s a whole lot of product for as little as the E17 retails for.