I was trying to understand the audio line output schematic shown below but couldn't make sense of it.
This circuit comes after the output of an Audio DAC PCM1725, followed by an active 1st order low pass filter (opamp partially shown in this picture - top, left), followed by the final stage circuit as shown. There's nothing else between this circuit and the output connector.
I've never seen anything like this and don't understand its purpose. Can someone more experienced help me understand it, or point me in the correct direction?
Thank you in advance for your time.