Step 10: Building the Circuit

At this point, all the on-board components are in their designated spots, but like I mentioned before there are still some more connections to make. The first one is between the 0.22μF capacitor and pin 6. The second connection is between pin 2 and pin 4. This second connection could have been avoided if it had been done earlier by bending the 0.22μF capacitor's lead and connecting them between pin 2 and pin 4 instead of cutting it short like I did. 

There are still some more connections make across the board, but we'll do that later.
can i use other IC if i cant get LM386? <br>cause i cant find that part here, yet i found LM386n and LM386 9pins? <br> <br>or what else can i use, please help.
I'm pretty sure LM386n is the same as regular LM386.
I tried this circuit 2 times but all I heard was simply noise ??
How would one reduce the volume? mine is WAY too loud
<p>also the mic cable is twisted pair, makinf it a &quot;balanced cable&quot;. The circuit is unbalanced, so there is a mismatch. Use a shielded RCA cable instead and that will help alot. (Im experienced in audio equipment)</p>
<p>The noise is not a bonus, if you're trying to hear acoustic sounds... It is interference made by close by AM radio transmitters, sometimes FM but mostly AM is easiest to pick up in microphone cables etc. To resolve this, it needs a sturdy ground plane around the circuit, metal plate underneath, or a Faraday cage (metal box) Altoids can?? instead of the plastic enclosure shown. The circuit should be grounded via a jumper and insulated from the box.</p>
<p>can i use lm358 instead of lm386?</p>
<p>hi ernie666, I made one, not very fine for the testing. I can only have big noise, what's wrong?</p><p>adam</p>
<p>Did you perhaps put this on a breadboard? Maybe try soldering it on a perfboard. </p>
<p>I just tried this circuit with the same components except used 10uf between pin 1 and 8. It works really great using earphones and have little noise. </p>
<p>I also hooked the output to another LM386 and I can hear my own breathing. </p>
<p>Try this out, and see if it works for ya. I got a little higher gain with less noise.</p>
<p>Oh, and I saw that post earlier about using 18v. Only the LM386N-4 can take 18v, and even then you could cause damage to the chip. Be careful. You may not even want to take it to 12v. At least 9v, but closer to 10v would probably be good.</p>
<p>Did not work great with a 9V battery. Changed to a 14,4v one and almost blew my eardrums. :D But getting a 12V battery tomorrow and already built a case with an on-off button</p>
Very well explained.
hey dude :D <br>can i use other IC's if there is no lm386 available in my country?? <br> <br>will it be same diagram?
Can anyone give me a schematic of a spy ear circuit with 6 volts as source???
Can someone please help me? I have constructed this and double checked everything, but it does not work. All i hear is a clicking buzzing sound! Please help!
Please help! It can only pick up audio if i am talking like 1 inch away from the mic, i have checked my circuitry, and i have fiddled with the volume! Please help!
Where will i get a LM386 chip? <br>
In India we don't have RADIOSHACK-like stores, so I want your help. <br>Thanx in advance for answering!
Try www.digikey.com
ernie666- <br>I hv a question- I got the lm386 but wat can i use instead of the 1uf tantalum and 0.22 uf capacitors? i dnt hv dem!!
ok thnx dude <br>!
One question. Which side is the front of the IC? I'm assuming its on the right of the schematic. What is the pin load out? Where is 1 and where is 8? Thanks (I'm new to this :D) <br>Would a 9v battery work fine?
Can spy ear be done with wireless earphones???
I don't see why it can't be done. You should try it
thanks :)
we didn't get any output for this circuit with 9v. whether we need to change any resistor or capacitor value? advise us with value. <br>
You might want to check your circuit. LM386 chip has a wide supply voltage range. Maybe you connected the capacitors or microphone the wrong way, or maybe a component is broken. <br>
reply us as fast as u can
On the schematic, what are the pin numbers?
oops. I forgot about that. The bottom left pin is pin 1 and the rest of the pins are numbered like it would be on a regular 8 pin DIP chip if you were to look straight down on it from the top <br>
You should enter this in the kit challenge. You would have a chance! <br>-Doctordv
hey! I just wanted to ask that how much was the distance from which you can catch the sound and don't the wall's muffle the sound? I'm making it as my final semester project so want a pronto reply. :) waiting...
I'm sorry, i tried that with hooking up a speaker, i heard nothing sorry.. :(
can i use instead of 12V...9v ! if i replace the resistors with another numbers <br>?
yes with 9v and different value resistors, but you should probably test them first because too much input power could cause distorted output
or the capacitors!? plz reply ASAP
guys try shielded cable for noise interference definitely u will get results...
its good <br>
The problem I've always had with anything that allows you to pick up sounds at a distance is that they amplify the background noise as well. <br>Would it be possible to add something similar to the technology used in noise-cancelling headphones to cancel out at least the sounds generated closer to the microphone?
Noise cancelling headphones simply block sounds around you, so no this could not be used to solve this problem. If the noise is at a certain frequency, you could add a high/low pass filter, otherwise I don't think this problem could be solved without software. But you could focus on what you want to hear by adding a parabolic reflector like blinkyblinky suggested.
I used a parabolic dish but still there was background noise, most of which came from much closer to me than the sounds I was trying to pick up. I didn't mean use noise cancelling headphones themselves to counteract this, I meant employ the technology that they use and integrate it into the circuit. <br>As I understand it noise cancelling headphones use a small microphone to pick up sounds just outside the headphones then play the inverse to cancel out the external noise with destructive interference. Would it not be possible to integrate this somehow in order to filter out the noise coming from closer to you so you're just hearing the sounds from further away? <br>Other than that, I think you're right and having various filters to tune out the frequencies you don't want would be the way to go.
That sounds like a brilliant idea but I can't think of how to do that just yet. I'll try to figure out how to do this, and if I ever do, I'll write about it.
Thanks, that'd be really awesome. I wish I could help but electronics is still on my to-do list.
can i connect signal output to 2 pins of earphone to turn on speakers in both ears?? reply fast

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