My project requires me to use an electret microphone and I am having a lot of trouble getting any decent-sized signal out of it. I currently have it configured with a 100Kohm pullup resistor and a 47uF capacitor. The signal is so weak that even if I put it through an amp with 200V/V gain, I only get an output whenever I tap the microphone or blare music straight into it with my earphones. Is there a trick to using the microphone right or do I just have a crappy one? I don't know the model because my professor didn't provide it, but 54LO is printed on the top.


1 Answer 1


2 wires or 3?
Polarity known to be correct?
What DC feed voltage?

100k sounds high.
Try 10k

Sensitivity ratings are usually wrt 1V/Pascal = 1 V/ 94 dB Sound Pressure Level.

1V/Pascal = 94 dB SPL = "loud and close"

Real world sensitivities may be 40 - 70 dB below that (!).

-60 dB ~= 1 mV/Pascal.
-40 Db ~= 10 mV/Pascal.

This may not be far off what you are seeing depending on the mic you have and what signal level you require.

So with a 200V/V amplifier and a loud signal you'd expect about 200 mV from a -60 dB sensitivity microphone with a rather loud signal.
And 2V with a -40 dB mic.

Microphone output and gain calculator here

Nicely done amplifer article here - note input DC bias resistor needed for electret.

Many potential circuits here BUT you need to have some idea of basic specs and correct connection.

Example Hosiden mic spec sheet - all at -45 dB sensitivity.

2 transistor electret mic preamp useful.

Another similar useful


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