My AIM is to feed audio to mobile phones over MIC IN port. This audio would be coming from Laptop's headset out port. The way i am testing is making call from the test device which is connected to my laptop. What is want is to hear the audio which been played on system at the call termination mobile device. I tested the these two circuits and here are my observation :

Circuit 1 : NO audio received at the terminating mobile. May be the resistor values are too high. I didn't tired with lower resistor values.

Circuit 2 : Audio was received at the terminating mobile device but was very low. I removed resistor and capacitor both and tested directly.Audio became loud enough but quality was poor. There was too much of 'air' like audio with some high peak audio loss too. i just connected capacitor and tested. Audio became little low but quality was still poor.

Please suggest how this conversion is possible, maintaining high audio quality ? May be i am using too high capacitor and resistor?

Circuit 1:

Circuit 1

Circuit 2:

enter image description here


This will take the headphone/speaker/line level output from a typical laptop or tablet or music player (or even another phone). It will attenuate it down to microphone level, and then C1 will block the DC voltage out of the mic input jack on the destination gadget.


simulate this circuit – Schematic created using CircuitLab


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