This is a demo board I created to test the I2S PCM1808 DAC. An XTAL oscillator based on SN74LVC1GX04 generates the DAC SCKI clock signal, and a very low-power DC-DC boost converter is responsible for powering the analog circuitry. The signal from a microphone is amplified and filtered before entering the DAC.
Test with Raspberry Pi
The initial test involved connecting this circuit to a Raspberry Pi configured to use the I2S interface as the main audio input.
With the help of Audacity software, it was possible to visualize the waveforms and listen to the recorded sounds.
Test with ESP32 devkit
After verifying the basic functionality of the circuit, I connected it to the final demo circuit based on the ESP32 SoC.
This testing phase aimed to determine the best gain value of the preamp and the component values for the LPF (Low Pass Filter) filtering.
Oscilloscope plot of the MIC output signal and the preamp input.
Oscilloscope plot of the preamp input and output signals.
Oscilloscope plot of the preamp output signal the DAC input.
ing DIY 
