Fiio E17K (Alpen 2) Portable Headphone Amplifier with USB DAC. The FiiO E17K is a portable lightweight brushed metal headphone amplifier and digital to analogue converter (DAC). The E17K model is FiiO's replacement of the very popular E17. The E17K features a control wheel for volume adjustment, an upgrade in the DAC specifications as well as new headphone amp components. It's also thinner and more powerful than the E17. The E17K has fewer buttons on the front than that of its predecessor the E17 making it much sleeker and easier to use. It features a new multi-functional wheel that responds to both turns and clicks, providing an intuitive agile control replacing many buttons from the older model. So buy this Fiio E17K (Alpen 2) Portable Headphone Amplifier with USB DAC Now £99.00.