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Microphone amplifier Issues ...

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Mr CCE

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Hi all,

I'm lately building an amplifier for an electric microphone but I'm getting nowhere. I tried a non-inverting amplifier-741- with a gain of 100 and then a gain of 1000 but still there's no luck.

Sometimes I'm getting a -ve voltage (in a non-inverting amplifier!). Also, If I connected the mic directly to a voltmeter would I get a voltage? say, in the mV range? and if not, does it mean the mic is dead?

thx.
 
The Capacitor Type of MIC will give good response to your audio signals, you can measure its ohmic resistance is Varying by The sound level by puting your Multimeter in 1 Mega Ohms range...., Now you can measure the current you can get from the mic to amplify, If it is Micro Amp range The 741 may not be able to pick it as it has less amplitude level to respond its input transistors, But you are able to do it with FET input operational amplifiers... that will satisfy your need.....
 
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The Capacitor Type of MIC will give good response to your audio signals, you can measure its ohmic resistance is Varying by The sound level by puting your Multimeter in 1 Mega Ohms range...., Now you can measure the current you can get from the mic to amplify, If it is Micro Amp range The 741 may not be able to pick it as it has less amplitude level to respond its input transistors, But you are able to do it with FET input operational amplifiers... that will satisfy your need.....

No idea what he's talking about?, if you want to test it, use a scope NOT a meter. Use the preamp and power circuit posted on here many times by Audioguru.
 
If Mr CCE is not having the Scope ? , Then what he will use ? Do you thing that he will not get this circuit simply by searching Google ? He want to make his on try.....

Understand man, I am giving source for him to learn.....!

If he is able to get the resistance level he is able to find the current by which he has given to the MIC +ve pin, Output from its - Ve ..... You are SO advanced Mr. Nigel Goodwin
but there are some ways to do everything by simple ways........!
 
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If you're using an electret microphone it'll need a bias current (e.g. use a pullup resistor). Then capacitively-couple the signal into the +ve input. Make sure the +ve input is biased to you reference voltage (via another resistor).

If it's a dynamic microphone, do all the above, but omit the microphone bias current.
 
If he is able to get the resistance level he is able to find the current by which he has given to the MIC +ve pin, Output from its - Ve ..... You are SO advanced Mr. Nigel Goodwin
but there are some ways to do everything by simple ways........!

An electret mike requires a power supply to work, you can't simply read the resistance of the output FET without it being powered.
 
I just tried it:
1) My multimeter set to measure OHMS has a voltage of 0.2V max. When it is powering an electret mic the resistance (2.2k ohms) changes when I hit the mic on the table.
2) My multimeter set to DIODE TEST has an output of about 3.5V. When it is powering an electret mic then the voltage reading (1.4V) changes when I hit the mic on the table.

The meter is reading DC, not AC. The mic is producing AC but the sharp knock produces a DC spike that is shown.

The amount of force and the voltage are not calibrated so the test is nearly useless.
 
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