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[on:]

I am feeding audio from a Sound module wtv020sd-mini which is PWM , to the mic Pins of My GSM Module Sim900, when I hear this sound on a a speaker although its not a high quality still its fair enough, but when I play the same voice and feed it to Sim900 mic and listen to it over a call its quality is very poor, there are alot of humming sounds and voice quality itself is also low.

I wanna use the module for voice response to callers , Is it all because of PWM output ? I used another module from ISD17150 and its voice quality is very nice even on the call.

[Reply #1 on:]

That link is bad.

So I am unsure what you mean by "which is PWM"
It is unlikely that the output is actually PWM.

but when I play the same voice and feed it to Sim900 mic

Again it is not clear what you are doing. You seem to be saying that you are feeding a sound signal into a microphone and using it as a speaker. Surly that is not what you are doing?