DAC-80 is designed to remove hum and buzz created by ground loops.
Normal voltage differences in the system grounding points between different pieces of equipment cause small AC power currents to flow in the shield of audio cables.
Capacitance between a power transformer's primary and secondary windings introduce signals to the circuit ground which will also create small current flows in the cable shield.
Either of these problems will create hum in audio signals. DAC-80 breaks the interequipment ground path and greatly increases the rejection in the input circuits while remaining transparent to the audio signal.