ADAU1772 Output ASRC Source Select

bklein Question

Mar 13, 2023 00:00

Please explain the Output ASRC Source Select. I have been using the Core Out X selections but wonder about ADC X selections. They do not seem to have the same levels as the Core outputs. Are they basically using the inputs to the DSP core rather than the outputs? Why not the same level if no level changes are made in the DSP core (straight through no "effects")? Once this resolved should it show a better S/N result if testing ADC > serial out?

software

adau1772

Integrated/Special Purpose A/D Converters

Audio CODECs

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DaveThib Reply

Mar 13, 2023 00:00

Hello bklein,

I do not have a great answer for you. There were some gain errors in the design through the system. I have never received a good explanation from the designers. It is written up in the datasheet but it still says "approximately" and I think this diagram is still not correct. You will see about 2.5dB differences in places so it is not anything you are doing wrong.

This section of the datasheet makes an attempt to show the level differences but it does not seem to be fully correct.

You are correct that the level out of the core should be at the same level as coming directly from the ADCs. This diagram in SigmaStudio shows it well.

There is a possibility that you could have a clocking problem. Can you attach your project and let me know what frequency the master clock is running at? Let me know the levels you are seeing and I can verify I have the same measurements here.

Thanks,

Dave T