ADAU1701 MID EQUALIZER NOISE

Hello fpg,

This is really hard to tell from afar. I do see you are boosting a lot of the high frequency. so that might be making the problem worse. 

You could have a ground loop with USB power and interfaces and you could be getting a buzz from the audio out of a computer. I have had to deal with that often on my desktop setup. I will get audio from my MAC and there will be a ground loop to my PC and it is often a buzzing noise sounding like data not a ground buzz. 

Remove the inputs.

Mute the inputs in the DSP. 

You have a mute on the outputs. What happens when you mute those? 

Add a mute right at the input of the DSP core. 

Are you using double precision filters? That can create a noise floor when you have low frequency filters. 

From what I can see it does not look like you are adding a lot of gain.  

What hardware are you using?

Dave T