Dsp board

You probably want to run the ADCs on clean power separate from the DSP?
It's indifferent.
You would probably want to make sure you understand what features the DSP you want to use has. Implementing submix busses and or other features may not be as easy in some chips.
For now just want to convert line in/out signal from adc.
Also, how will the user interact with the DSP, via computer over USB? With dedicated knobs, switches, and display? A touchscreen?
Is a simple usb audio class 2 device without any more features for user interact. Or maybe I could follow the Dante option that rfbrw writer.
Need mic pres and phantom power built in too? Adjustible preamp gain? 20dB attenuators in each channel?
Just an jack line in/out plug in each channel.
 
You said this was for a digital mixer? How will you mix, assign channels to submix busses, etc.? Not using this?

Did you really mean this is to be a USB ADC without DSP?

Do you need realtime low latency for a stage mix, for house mix?

Still not quite clear on the goal here...
 
You said this was for a digital mixer? How will you mix, assign channels to submix busses, etc.? Not using this?
Yes, I said this was for a digital mixer? For a first stage it could be only an audio interface that only send or receive line signal over usb or Dante or other options. Mixing or another things only in date.
Did you really mean this is to be a USB ADC without DSP?
Yes
Do you need realtime low latency for a stage mix, for house mix?
In my mind I can do vst effects with audio received from the device I am projecting in daw and output this in an lineout jack in my device . There is always some latency. An understandable latency level is needed. But I could simplify the project not doing output part. Because this thing could makes using two cheapest boards instead one.

I founded various YouTube videos saying how do an sound mixer with all effects, but there haven't any digital part. I can adapt the ins connector from an analog mixer because is line level to send and receive to my projected device doing an direct connection . Even can get an way to make ins connector available for another thing but we don't need it, but I think do it with an Arduino or another way.
 
I know some musicians that complain they can't perform with 10ms monitor latency. They need it 5ms or less.

Anyway, problem is fairly simple if all you want to do is hook up some ADCs to a multi-channel USB interface. You will still have to figure out how to clock everything so the chips can work together. That or maybe ASRC, but that may add more chips and complexity.
 
The module allows you to select 1 of 4 possible inputs. Only one input device is active at a time.

Besides I already explained what you need to do. A USB board or MCU that can act as I2S 'master' must generate BCLK and LRCK. MCLK will probably have to be generated by a standalone clock module that also clocks the USB board or possibly the USB MCU. Each ADC will operate in 'slave' mode meaning that the audio clocks are externally generated outside of the ADC chip (clocks are generated by the USB board instead). Each ADC will output one data line. The USB board or MCU interface must have 16-inputs for data, one for each ADC chip.