What is the configuration of the microphone amplifiers? At a guess, it is an op-amp with the inverting input connected to the mic input via a resistor, and the non-inverting input connected to the reference, and gain setting resistors selected by the gain setting. Is that correct?
My microphone is at some distance from the codec, and therefore requires a balanced line input and which I am trying to design with the minimum number of extra components. Therefore I would like to know how the pins are connected.
It is a pseudo-balanced so I suggest you use an external amp that is fully differential and then drive the input of the codec. This will yield the best results.