Impedence determination of a given mic

FvM said:

Seriously speaking, I don't see a particular need to measure microphone impedances because they are mostly well specified. But it's possible of course. The microphone output signal will be reduced to 50 percent if you load it with it's output impedance (impedance matching case).

For an accurate measurement, you'll use an audio frequency signal generator, a known series resistance, and an AC millivoltmeter or oscilloscope.

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Audioguru said:

A condenser mic needs an external 48V to bias its diaphragm. Maybe you have a more modern electret mic that is a condenser mic with the high voltage permanently set in its electret material and it has a built-in Jfet impedance reducer. Its impedance is about 3.3k ohms but the resistor that powers it is effectively in parallel so the total impedance is about 2.5k ohms.

A dynamic mic has a cone, coil and magnet like a little loudspeaker. Its impedance is from 150 ohms to 1200 ohms but is usually 600 ohms.

The output levels of different mic types are low and are about the same. They need a preamp.

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Audioguru said:

Maybe instead of a condenser mic you have an electret mic that has 3 wires. Its output impedance is about 600 ohms because the output is from the source of the Jfet. The higher output impedance of a 2-wires electret mic is from the drain of the Jfet.

A preamp is simply a non-inverting audio opamp with a gain of about 200.
Here is one for a 2-wires electret mic:

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rajaram04 said:

i have only 2 terminal condencer mic

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Audioguru said:

No.
You probably have an electret mic./

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