Connecting an electret microphone to an ESP32 via MCP3424
You have two issues.

Your Mic needs power, see the application schematic in the datasheet.

Since the Mic is referenced to ground because of the power, you must bias the input. You need an opamp that will function with a small power voltage. An LMC6482 is a nice one, but it is expensive. The opamp can be shared with multiple inputs.


If you can live with an offset when no input is present, you could remove the opamp, and bias the positive and negative inputs separately with 4 resistors, 100k to +3.3 and Ground for each input. The resistor tolerances will cause a non-zero offset.
You could also use a voltage reference of about 1.5V or so instead of the opamp.




simulate this circuit &ndash; Schematic created using CircuitLab