Although Wolfson Microelectronics produces some fine integrated circuits, website their application note section is somewhat out of the way and doesn’t like to be linked to directly. This didn’t stop me from looking around and finding some potentially useful app notes:
The main reason that I was looking there in the first place was that I was getting excessive noise when coupling a portable audio player to an audio system I am working on and couldn’t figure out why. When I took everything apart, I found that output stage of the audio device was being pulled up to a higher voltage than expected by the coupling on the input stage and thereby biasing the input stage of the audio amplifier incorrectly. After some careful circuit modifications, the signal integrity was returned with fairly good low frequency response. At this point, my audio circuit experience is still minimal, I hope to post some designs once I get something worthwhile going.