[bighat]

I made this microphone to be able to make fast and dirty measurements with my phone,
because of the fact that cellphone internal mic signal is digitally processed, bandwidth limited.
I have tested it on android phone with fft and osciloscope and it's working, how much is it reliable? don't know.
 
parts
6mm diameter cheap noname electret mic
17kohm resistor (I have measured HTC headset resistance between ring,tip and ground)
 
 

 

[Music818]

The 17k ohm resistor is useless and may damage your phone's audio output.

 

[bighat]

Thanks for answer,
I think you are right I have measured the resistance on jack between mic ring and headphone ring.
Without this 17k resistor this diy mic won't work on my cheap android phone.
Can such a high resistance load damage phone audio output?
Where is my fault?

 

[Music818]

In some phones, the MIC terminal will always output a DC bias voltage (1.xV to 2.xV) for the MIC to function. So, the DC voltage may damage the audio output. You just need to connect your MIC to the MIC pole and ground pole correctly. To activate the MIC function of the phone, you may try to make a short circuit (for <1 second) across the MIC and ground terminals, somewhat like you press the MIC button on a remote to receive a call.

 

[bighat]

To activate the MIC function of the phone, you may try to make a short circuit (for <1 second) across the MIC and ground terminals, somewhat like you press the MIC button on a remote to receive a call.

in such small design it's not possible.
Android specification use mic r=2,2kohm for 2,2 bias voltage
http://source.android.com/accessories/headset/specification.html
 
I havent tested it, but according to google specs diy mic should look like that...

 

Ear speaker impedance | 16 ohms or higher | Recommend 32 - 300 ohms
Mic DC resistance | 1000 ohms or higher

Is this correct?

 

[Music818]

  in such small design it's not possible.
Android specification use mic r=2,2kohm for 2,2 bias voltage
http://source.android.com/accessories/headset/specification.html
 
I havent tested it, but according to google specs diy mic should look like that...

 
Is this correct?

 
 
Actually the MIC connection should be only related to the MIC and ground terminals. 
 
The 32 ohm resistor from the L/R terminals is useless to the MIC function. 32 ohm is a suggested impedance of loading (that's the headphone driver impedance) for the mobile phone's headphone output terminal.......Without the resistor, the MIC should still work. May be you can replace the resistor with a driver (commonly 16 ohm - 32 ohm). Then, you can hear back what you've recorded.