The 0dBFS level of the PCM1804 is a little ambiguous from the data sheet.
The banner specifications give +/-2.5 V (Vpk, Vpp, Vrms, unspecified):
Whereas the recommended operating conditions specifies 5 Vpp:
The electrical characteristics gives again +/-2.5 V differential (again, without Vpk, Vp, Vrms specified):
The DC operating point of each input is 2.5V.
The linked post: PCM1804: Analog input, says the example therein is wrong, and that the reading I propose below is correct. However, the example is the exact circuit used and documented in the PCM1804 eval kit design.
Additionally, the 5 Vpp differential specified in the datasheet seems to describe a maximum input level when measured across the differential input of 5 Vpp, implying one leg at -2.5V and the other at +2.5V relative the DC operating point. This agrees with the eval kit description.
My assumption is that the fullscale input range of each leg is: -1.25Vpk to +1.25Vpk (referenced to the 2.5V operating point), or +1.25V to +3.25V (referenced to 0V ground). Is this correct?