FiiO E9 and E7 Bundle Desktop and Portable Headphone Amplifier with USB DAC Includes powerful E9 desktop headphone amplifier and portable E7 headphone amp and USB DAC Ultra low noise and low distortion with enough power output to drive 600Ohm headphones Smooth and low noise ALPS sealed potentiometer for volume control Audio buffers using ultra-low distortion and low noise Burr-Brown OPA2134 op amps High accuracy USB DAC for optimal music playback from a computer