Sennheiser HDV 820 CN Headphone AmplifierMaximizing headphone performance The HDV 820 is a reference grade solution for critical listening tasks. Maximize your headphone's 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. Our HDV 820 treats virtually any source or dynamic headphone to over 75 years