The PCSTEP is a portable amplifier that, in addition to its analog input, also has a built-in USB-DAC. When connected to the USB-port of your PC it will strongly improve on the sound that is provided by a standard quality soundcard.
The amp has a discrete volume control (32 positions, two gain settings). This volume control is not a standard industrial solution but uses a concept in which the position of an analog potentiometer is measured using a low-power ADC and in which the output of this ADC is used to control electronic switches that set the volume level. The result is a very clean and detailed sound without any channel imbalances.