There is a bug in a documentation for PCM3168 and in User's Guide for motherboard for PCM3168 . How this circuit converts differential signal to single-ended? You should add some DC on non-inverted input, if not signal after conversion has reference voltage on AGND and negative part of the signal is cutting off.
This is a part of User's Guide for motherboard for PCM3168:
This is a part of PCM3168 datasheet:
Could you explain this strange situation?