Picture of Pre-amp to electret mic!
This circuit is very easy to do!
and all parts of it are easy to find!
It is nice to put together with design of Rtty21
"The easy transmitter am"
so you can talk on the radio or put somewhere
hear the conversations of others!
the parts you'll need for this project will be!
Q1 = 2N3904
R1 = 10k
R2 = 100k
R3 = 10k
C1 = 0.1μf or if you prefer 104 or 100n
C2 = 0.1μf or if you prefer 104 or 100n
MIC1 = a common electret microphone
to put it together to design rtty21
and just put the place marked as output to next stage
pin 4 for the 555 (ne555/lm555/7555/ka555)
and ready to feed it to the same source of another circuit!
                                                                 My First Instructables
                                                                     Yeah!!!!  XD
                       with some debt and send a comment I will try to solve your problem!
ElleK11 month ago

Hi, I'm looking to amplify the voltage from an electret mic in order to make a VU meter- do you know whether this circuit would do the trick? If so, do you have any idea of the voltage gain on this pre-amp?

Any help would be much appreciated! ^-^

jowarkz1 month ago

good day . I need help , what to do to make an electret mic more sensitive?

Im making a clap switch using a bc547 transistor . I connected the negative pin of the mic directly to the base of transisitor , I observed that its not that sensitive . what should I do to make it more sensitive? please help . Thank you so much

lukas_tek (author)  jowarkz1 month ago
I think you need to connect the positive pin of the mic to the base of the transistor.
CameronF7 months ago


I attached this to my ipod amplifier, wired it to a speaker, and now peacefully listen to the outdoors from my basement.

Really good for your first instructable!

Lentamentalisk12 months ago

Can anyone suggest where to modify this to increase the amplification?

I am getting ~100-150mV for everything below 100dB, and at 100dB+ it rapidly rises up into the 2V range. I'd love to get some more definition in the 70-100dB range, even if I lose it in the 100+dB range.


I just answered my own question. To change the amplification, change the 100k resistor value. I believe doubling the resistance doubles the amplification.

hey lucas can this preamp be used for normal mobile audio
mamundsen2 years ago
This is sweet. I bought some super cheap electret mikes recently, and this is the third preamp I've tried to build. It's also the only one that works well. (I got a very nice progression from the first circuit as not working at all, to the second one working poorly and now this one working satisfactorily.
pinst3 years ago
Could someone help a newbie add a low-pass filter to this design? I have an electret mic with a frequency response of 20-20000HZ but wish to filter out frequencies above 300HZ.

ASCAS pinst2 years ago
make a simple audio crossover.
maixy3 years ago
i have been wishing to make an amp
but i do not know too much the knowledge of electronic
i will appricate you if you can add some explanation to it
lukas_tek (author)  maixy3 years ago
i start with eletronic like this
burn led on 220v,open light bulbs,making motors turn on with a battery
this things
framistan3 years ago
A very usefull schematic. I am printing this out on 3x5 card and will certainly use it. thanks.
lukas_tek (author)  framistan3 years ago
thanks for you !
because you see my instructables!
is this the combination for the circuit of rtty21?
lukas_tek (author)  oteng09143 years ago
May be because if you want a voice in the radio station you need a pre-amp to the mic , cause the mic alone don't make sound!
jensenr303 years ago
this looks nice.
I should try it sometime.