The HD20 offers a significant improvement compared to its little brothers. Both in terms of sound quality and functionality. The HD20 has both USB inputs as well as regular coaxial and optical spdif inputs. The HD20 also has a Hegel system remote control that can be used to control the HD20 as well as other Hegel components. The big thing with Hegel digital to analog converters is that we are able to get very high quality sound from standard audio players like computers or iPOD type units. The problem with these common players is that they send out the digital data in an uneven rate. This is called jitter, and results in a smeared sound with less dynamics and detail. The Hegel DAC’s incorporates technology that store the data stream and build it up again in exactly the correct rhythm. Thus reducing the effects of the quality of both the computer and the digital cable. The HD20 also has a new impedance matching technology developed by Hegel. With this we can adjust for the less than perfect impedance in normal RCA digital cables. This further reduce the jitter, resulting in increased precision.