Upgraded DAC Chips
The ES9028Q2M DAC chips on the original R3 have been upgraded to dual CS43143 DACs. The upgrade promises improved signal to noise ratio and reduced distortion.
Increased Battery Life
Hiby hasn’t also boosted its battery capacity, it is still 1600mAh. But the original R3 offers about 10 hours playback while R3 pro could offer about 20 hours through the 3.5mm connection and about 16 hours using a balanced connection according to Hiby announcement officially. I think so many improvements may due to the upgraded chips of DAC and BlueTooth.