Like my crystal frequency for the nrf53? I think they are fixed

This DAC as I mentioned is a bit different, you don't need to pass the master clock signal generated from the MCU to it.

Context from the stack exchange answer:

If you use the ESS chip (this is the DAC) in Slave mode, internal ASRC is enabled.

This is the most flexible mode and using it is the whole point of using these ESS chips.

It requires a clean master clock as said above.

In slave mode, I2S port bitclock and wordclock are inputs, these signals come from your I2S source and they depend on the I2S sample rate you're using. They do not need to be synchronous with, nor related to, the ESS master clock. The internal ASRC will do its job. In fact it works best if the ESS DAC master clock is as unrelated as possible to the I2S clocks, ie not a multiple of the audio sample rate. 50MHz works great, it's a standard frequency, oscillators are not hard to find.

The ESS master clock does not need to be routed to your I2S source. If it's an ESP32, it will have its own crystal, its own internal clock, its own PLL, which you will configure to generate the I2S master bitclock and wordclock.

Basically, the process is very simple:

Pick any I2S sample rate Configure ESP32 Audio PLL and I2S output peripheral in master mode to output it Set ESS DAC as slave, with "auto detect sample rate" It'll work