Problem with microphone preamplifier circuit

[amirahmadian]

Hi,
Please have a look at this circuit which I use to amplify the output signal of a capacitor microphone. I watch the output of the circuit on a oscilloscope, but it seems to be random noise.When I speak to the mic I can't see anything similar to audio signal on the output. Only when I hit the mic with my finger, I see the signal level increasing for a moment! Anyway the amplitude doesn't exceed 50mV.
Dou you think there is something wrong in this circuit? Or I have implemented it incorrectly? Or maybe these results are normal?

 

[KerimF]

Your circuit seems ok. Perhaps there is a minor mistake in the connections on the breadboard.

 

[E-design]

Try removing R2. You are lowering your sensitivity with a electret mic. https://en.wikipedia.org/wiki/Electret_microphone
This sort of biasing will only work with a condencer type mic. https://en.wikipedia.org/wiki/Microphone#Condenser_microphone

 

[Usama Siddiqui]

try simulating it first by giving some analog values at input.

 

[Audioguru]

You do not have a condenser mic that needs a 48V supply. Instead you have an electret mic that has the 48V built into the electret material.
It needs a preamp with a gain of about 200 times but your circuit has maximum gain of about only 27.3 times.

The electret mic has an output impedance of about 3.3k ohms which is parallel to the 10k resistor that powers it then their total is 2.5k ohms which is in series with R1. R2 is not needed since it reduces the output level.

Your first opamp is inverting with a very low input impedance of only 2.2k ohms that shorts the output level from the fairly high impedance mic. This opamp should be non-inverting so it can have an impedance of about 33k ohms or more.

Both opamps should have higher gain for a total of 200.