To obtain the best performance from the AD193x family of codecs, good PCB layout practices must be used.
This does apply to almost any other part since the subject is correct connections to and from bypass capacitors and also for things like loop filter components.
I have responded on the forum and via email to many customer issues with these parts that were all caused by poor PCB layouts.
I have prepared a document that details the correct practices using mostly pictures.
Please download the attachment for more information.