Well here I am feeling like an utter fool but I really need to get this working. I get heavy distortion when I use my ADAU1701 and I'd dare say that the reason for this is that the input circuits parameters are all wrong (i.e. the analog input is being over-driven). I know what the recommended settings are but I just can't seem to find how to configure them!
So to sum it up: How do one configure the AUX input circuits?