do you think that by inserting a filter on AVDD as visible in the attached image, it is possible to improve the noise on the internal analog circuits on ADAU1701 more?
This is always a good idea and may help but it all depends on the nature of the noise and where the noise is coming from. I am a big advocate for properly placing bypass caps to make them more effective at keeping noise from the power planes out of a part, but it also works the other way, it helps keep noise from within the part from going out onto the plane. So the cleaner the power planes the quieter the audio will be.
Then there is the important detail of proper transmission lines for the clock and data signals. If they have a lot of over and undershoot, then they will be dumping noise energy onto the power and ground planes that you will have to try to remove afterwards. So preventing the noise at the source is much easier to do.
Then it is good to have many "stitching caps" around the PCB to keep the digital noise down on the ground and power planes.
I have seen the techniques I have mentioned above lower the noise floor a great deal in systems where it was not done well. somewhere around 10 to 15 dB.
These are big subjects, I have written a lot about this on the forum and there are many books about the subject of Signal Integrity.
Do a quick search of the forum. I can look later for some.
Thanks Dave I will do the search in the forum.
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