Applicable to our A2+, HD3, and HD4 speaker models
All digital audio sources will ultimately need to be converted to analog to provide sound through any speaker system. The USB and Bluetooth inputs will pass the digital signal on to the speaker's internal digital-to-analog converter (DAC), while the RCA/3.5mm inputs are already analog and have been converted by the built-in DAC in your source. So it's a question of which DAC sounds best to you. We would recommend testing each input separately to see which one you prefer!