I'm working on a project that deals with voice signals and must meet Voice Grade 8 requirements. Most of the requirements are met except for the intermodulation distortion. I'm using an ADAU1442 processor running a program that takes In 0 and directs it right back out Out 0, so I could eliminate the software being the cause of the problem. I've looked through the datasheet for the AD1938 and didn't see anything about it.
Could it be the ADC/DAC causing the intermodulation distortion, or should I look elsewhere (like the op-amp circuits)?