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 Rtty21http://www.instructables.com/id/Easy-AM-Transmitter/
"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!
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Can i use 2n222 transistor for this circuit
<p>I've made it and it working but i have to things to share and ask</p><p>My sittings :</p><p>I connected the circuit to an atx power supply regulated (through lm317) to 4.5v and thin the output is connected to an AUX of my setreo.</p><p>1-Problem is i am hearing a buzzing sound , why? And how do i reduce or eliminate it?</p><p>2- the mic isn't very sensitive, any ideas to improve it??</p>
<p>check this casing hehe...</p>
<p>Wow.It's awesome,I really like it.</p>
<p>This is pretty darn brilliant. As near as I can tell, the circuit finds its own point of stability, by self-correcting until the current through the base opens up the transistor exactly the right amount to be stable. (In other words, where V(ce) = V(b) + I(2)R(2), with V(b) as 0.7V.)</p><p>This circuit inspired me to finally, FINALLY build a common-emitter amplifier that seems to work to my satisfaction (see image). The electret microphone that it's connected to &quot;idles&quot; at about 4.5 V, and so does the transistor. It picks up sound well, oh and the transistor doesn't overheat and then go &quot;poof&quot; like with some of my previous attempts. :-) I don't know that this circuit is any better than the one lukas_tek gave us; mine's more complicated and you may find it doesn't work as well (YMMV). Nevertheless, it's an example of a standard common-emitter amplifier that works and is made of parts with pretty conventional values.</p>
<p>Really cool,I will try it later.</p>
<p>works fine, thank you!</p>
<p>So I've been fiddling with the featured circuit more, to see if I could control the circuit characteristics more precisely. In particular, I wanted a circuit that &quot;idles&quot; with a V(ce) of 4.5V (since I'm powering it with a 9V battery) and I want 20 mA going across R3. I also want the output from the microphone to center on 4.5V. Using datasheets, Kirchoff's Laws, arithmetic, and a little trial and error, I've come up with these recommendations:</p><p>R1 - 18k (this could vary depending on your electret microphone)</p><p>R2 - 68k</p><p>R3 - 220 ohm</p><p>This makes for a satisfyingly sensitive microphone, and the electrical characteristics are about where I want them to be. I could probably rejigger this so that it runs on less current, but then I'd also have to figure out new R2 and R3 values (since, for what I understand to be best performance (which you supposedly get when Vce is half of Vcc), the current is going to determine R3 and therefore R2).</p>
<p>... you know, a smarter person than me wouldn't have spent so much time trying to work with data sheets and algebra and so forth. It's two simple steps:</p><p>1) Once you've decided on the current you want at Q, that tells you what R3 needs to be: it's Vcc divided by current, divided by 2 (because the intention is for the drop across R3 to be half of Vcc, and the other half will be across the transistor).</p><p>2) How to figure out what R2 needs to be to keep the transistor at half of Vcc? Just hook up a potentiometer, and adjust it until the voltage across the transistor is indeed half of Vcc. Then measure the resistance on the potentiometer.</p><p>When I just did this, I ended up with 72k; pretty close to what I got via much more complicated means earlier. Except using the potentiometer it took me less than five seconds.</p>
<p>For R2 and R3, values of 470k and 1k seem to work pretty well too.</p>
<p>Is the output considered &quot;line level&quot; ?</p>
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.
<p>Keep improving your skills!</p>
hey lucas can this preamp be used for normal mobile audio <br>
<p>What do you want to do with it?</p>
<p>Awesome!</p><p>I attached this to my ipod amplifier, wired it to a speaker, and now peacefully listen to the outdoors from my basement.</p><p>Really good for your first instructable!</p>
<p>can I connect the output to my pc ?? I mean when I talk can I hear my voice to the speaker connected to my pc coz I want to build it and record </p>
<p>how can i connect this to a speaker?</p>
<p>At this point, if i connect it to a set of powered PC spekers or something similar via a 3.5mm jack, will It be aubible ?</p>
<p>Yes, the amp in your sound card will take care of it.</p>
<p>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?</p><p>Any help would be much appreciated! ^-^</p>
<p>good day . I need help , what to do to make an electret mic more sensitive?</p><p>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 </p>
I think you need to connect the positive pin of the mic to the base of the transistor.
<p>Can anyone suggest where to modify this to increase the amplification?</p><p> 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.</p><p>Thanks!</p>
<p>I just answered my own question. To change the amplification, change the 100k resistor value. I believe doubling the resistance doubles the amplification.</p>
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. <br> <br>Thanks!
make a simple audio crossover.
awesome!<br>i have been wishing to make an amp<br>but i do not know too much the knowledge of electronic <br>i will appricate you if you can add some explanation to it <br>thx
A very usefull schematic. I am printing this out on 3x5 card and will certainly use it. thanks.
thanks for you !<br>because you see my instructables!<br>
is this the combination for the circuit of rtty21?
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!
this looks nice.<br>I should try it sometime.

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