The master key to your music: the HDV 820 unlocks the potential of your Sennheiser headphone collection with class-leading DAC and headphone amplifier technology. With a plethora of state-of-the-art I/O and world-class conversion, its the go-to hub for all of your sources.The HDV 820 is a reference-grade solution for critical listening tasks, maximizing headphone performance with top-class digital-to-analog conversion and exquisite amplification. While transducer quality obviously directly impacts high-level response and speed, the path to total immersion requires optimum circuitry from input to output.