Reducing noise on ADC input pin.

[CReze.1]

Hi guys, I am using an STM32F446RE nucleo board with an electret microphone(Waveshare Sound Sensor v2). Currently I am trying to sample audio, store it in a buffer and output through the DAC to an amplifier to a headphone jack. I am sampling the ADC at a rate of 44.1 kHz and playing back at the same rate, the DAC and ADC are triggered using a timer and DMA is used to store and send audio using a buffer.

if I connect headphones directly to the output of the microphone, there is no noise on the signal, however when listening to the audio that gets sampled by the ADC and played back through the DAC, there is a lot of noise on the signal. I am using 8 bit resolution. I measured the voltage on the ADC pin while the ADC is running and it measures to be around 0.55 V. However if i decrease the sampling rate the voltage sits at roughly zero. How can I reduce this noise? I have tried changing the sampling time cycles but that didn't help.

TIA

[S.Ma]

Not an expert, maybe you should check the audio signal is AC coupled and centered for the ADC at mid voltage (VddA/2) ?

Now electret is high input impedence and speakers probably have an audio amplifier to boost the signal.

ADC requires low input impedence, so at least a follower op-amp maybe needed, otherwise the ADC will look like a dynamically on-off switched RC filter.