Introduction: Mic Stereo With Little Amp in a Pencil Box

Picture of Mic Stereo With Little Amp in a Pencil Box

Mic stereo with little amp in a pencil box, i build this for my project is a non-profit project about the Soundscapes and Field recordings. This box use with a MD-510n Minidisc recorder with Analogical IN.

Happy build!!!

Step 1: Parts

Picture of Parts

The goal of this project is reuse and use cheap parts, well in my country (Mexico) are a Shops with articles from China (China everywhere!!!), in this kind of Shop buy a metal boxes pencils (and other wondefull and usefull things for Build, Make and enjoy the DIY).

From my garbage electronic:

2 transistors NPN BC548 (experiment with others if you like for example: 2n2222, c1056, etc)

1 Jack plug Male Stereo

1 Switch

2 Electrec mic

1 Little piece of hose transparent from my old Acuarius Tank

1 Battery holder 2 AA

Various screws, and hole drills.

Step 2: Drill and Wires

Picture of Drill and Wires

Make a holes for jack stereo, hose, and for close the box. Make a wire for the Right and Left Channel electrec mic.

Step 3: Insert the Mics

Picture of Insert the Mics

Warm a little the transparent hose and insert the electrec mics.

Step 4: Put the Battery Holder

Picture of Put the Battery Holder

For this i use a square of "Fasters"

Step 5: The Funny Step HOMEBREW

Picture of The Funny Step HOMEBREW

Well this is the funny step "Electronic Homebrew" i use a broken PC monitor:

Step 6: Warm and Make Connections

Picture of Warm and Make Connections

Follow the circuit and make connections with the most beautiful style: UGLY STYLE ;-)

Step 7: Two Is Best of One

Picture of Two Is Best of One

On my project have a collaborate friends and make for they this boxes.

Step 8: Result

Picture of Result

I make Fieldrecordings, interviews, Sounscapes and other sounds things with this box and Sony Minidisc MD-510n, the follow links are a few examples about performance of this project:

Music box with White Cristhmas Theme
Music box with White Cristmas Theme

Soundscape from my city Tuxtla Gutierrez, Chiapas. Mexico
Soundscape from my city Tuxtla Gutierrez, Chiapas. Mexico

You are found others recordings:


khushal_kkk (author)2010-11-12

do this circuit works for a stereo system , like i designed a system in which 3.5mm stereo jack is used and i use to connect it to computer to listen song through speaker do this mic work with it if i talk in that would i be abble to transmitt my voice through this designed stereo mic.

llaven (author)khushal_kkk2010-11-12

This mic work verywell for PC but remember is for soundscapes records, i mean, is for record sound ambients.

NeoFusion (author)2010-11-07

i cant understand the circuit well, hmm why is that there is only 1 electret mic on the schematic? help here total noob and i want to make your project badly!

llaven (author)NeoFusion2010-11-08

Hi, because is the circuit for 1 channel, if you need 2 channels (Left and Right) just make twice and put in the same box, with same battery and switch but 2 mics of course.

ShaunHill (author)2008-07-15

I'm confused, is this an amp or a sound recorder?

llaven (author)ShaunHill2008-07-15

Hi, the project is a mic amp for use in Minidisc with Line in for field recording

GorillazMiko (author)2008-05-25

Awesome! Very easy, kind of, nicely done, very cool. I might try this out if possible. +5/5 stars.

llaven (author)GorillazMiko2008-05-26

Thanks for stars and words, if you make your own, please let me know and share photos!!

ranger_steve (author)2008-05-25

to make it more "beatifyl" u could use a pc board just a thought

llaven (author)ranger_steve2008-05-25

maybe, but the Ugly style is a great design!!! :-)

ranger_steve (author)llaven2008-05-25

yup. =)

baruc (author)2008-03-20

hola se ve muy bien, y como apenas empiezo en esto de la electronica lo he hecho en un protoboard, no copie el modelo de el ultimo post, porque use más bien tres resistencias en serie que me sumaron 480k en lugar de la de 470k, y use un transistor 2n2222A, ahora, el mic. sólo lo probe y si funciona, pero ya en el circuito cuando lo conecto a mi grabadora de voz(panasonic) o a mi lap, me entra un ruido muy fuerte como de interferencia, como un tiiiiiii... nose que pueda ser. me surgio la pregunta de para que me sirve entonces, talvez no necesite un preamp.. nose podria explicarme como lo puedo ocupar, y porque crees que tengo ese ruido? gracias.

llaven (author)baruc2008-04-08

Que tal baruc disculpa que te responda hasta ahora, al parecer hay una retroalimentación en tu circuito, prueba conectarlo en tu lap pero antes de eso abre la aplicación que controla el volúmen del micrófono, las lap tops traen integrado un preamplificador, y quizá también tu equipo panasonic, quizá lo único que requieres son los micrófonos que estan separados para poder grabar el ambiente del lugar, además la grabación debe de hacerse en dispositivos stereo es decir con canal derecho e izquierdo para una percepción binaural

baruc (author)llaven2008-04-08

gracias por responder. probare más y te escribo de nuevo igual con una foto de mi circuito. saludos

truax (author)2008-01-04

can anyone see something wrong with my circuit? i've tried all sorts of stuff and it won't work.. help!

llaven (author)truax2008-01-04

I dont see the terminal negative of jack connected to ground (-) in your circuit

truax (author)llaven2008-01-05

and i'm guessing the ground for the mic also should also be hooked up to the negative?

llaven (author)truax2008-01-05

yep, the ground for mic to negative of circuit (negative battery)

truax (author)llaven2008-01-05

hmm. something is still wrong. is it necessary to be using the BC-548 transistor?.. i have here the 2n2222.

llaven (author)truax2008-01-05

no matter, bc-548 or 2n2222, only be carefully with the Emisor, Base, Colector disposition:



truax (author)llaven2008-01-05

Thanks! it works now.. i'm a total newbie at all of this.. barely passed my first college class. It turns out I had the emitter and the collector switched around.

llaven (author)truax2008-01-05

again, i see the first picture, everything is all right (only the conection between negative and ground jack plug OUT).

watch the Electret polarity too:

mrwizardgi (author)2007-07-22

total noob here so i apologize up front...what would the db rating on these things be? meaning how loud could something get before you notice distortion? are these mainly for 'normal' everyday sounds or could i take these to a concert and make a live recording? again, i'm a total novice in all of this so any info would be appreciated. thanks! peace j-

llaven (author)mrwizardgi2007-07-23

hi Mr. Wizardgi :-) god technical questions but i dont have that graphics and others, im experiment on the field, make your own is easy and you only spend a few minutes.

In the website of my project, have a others examples with this tiny amp mic and Minidisc 510-N

For example:

Trip around public market from Comitán, Chiapas, México.

Traditional and ritual of Catholic Religion called "Entrada de flores" from Comitán, Chiapas. México.

Sound of bamboo

Trip around the Santo Domingo Ex convent from Chiapa de Corzo, Chiapas. México

I think the key of the success for this project is the Binaural Mics, the length between left and right mics is like separation in owns ears, that help for spacial sound, in second hand the digital quality from Minidisc is greate the whispers, and others "silence" sounds make the record you feel here in that places.

Equal peace for everyone

- Llaven

mrwizardgi (author)llaven2007-07-23

thanks so much! this looks really cool and i look forward to trying it out! thanks j-

Botfly (author)2007-06-21

Your wonderful project was the first I came across in my search, Llaven. I have since found more that may be of interest and use to you and others.

DIY Stereo Mic Rigs
Quiet American - Links
Rane - Selecting Mic Preamps

And there seem to lots of places from large stores to single guys in a shop who basically sell these fully constructed with a preamp. Price vary from ~$50 to $600 US. The capsule prices don't seem to vary all that much from what I've seen but there's a bit of work to find a pair to match so they sound good as a stereo pair in terms of gain and frequency and then various custom tweaks. I can't really comment or plug any of the following as I am still doing research and have not tried any but do a search on Core Sound, Church Audio, Sound Professionals and Squid Audio.

SacTownSue (author)Botfly2007-06-29

Botfly, thanks for the links llaven, thanks for the project. This is an excellent beginners project. I noticed that you posted this about 7 months ago and it's the only project of its kind on instructables. wow ? it looks like the only thing you are using the screw and washer for is to hold the plastic tubing in place. It seems like you could accomplish that with tape or glue. Or am I missing something?

llaven (author)SacTownSue2007-06-30

Hi, SacTownSue thanks for you comments, for put the plastic tubing i make a hole in the middle and a screw, for the mics warm a little then insert the mics.

firewire (author)2007-06-29


electronicfreak22 (author)2006-12-04

Awsome instructable. This might work in an Altoids tin.

erevos (author)electronicfreak222006-12-09

Damn! You guys really love those Altiods tins!!! Too bad we don't have them here in Greece... :(

SacTownSue (author)erevos2007-06-29

maybe you should start importing them. Become a distributor. I buy them on sale at Walgreen's 2/$2. $1 a tin and free gum or mints. can't beat it!

I'll send you some for $500

llaven (author)erevos2006-12-09

But the tin of this project is not an Altoids is a pencil box.

James (pseudo-geek) (author)2007-04-21

BTW the modern term for "microfared" is uF not MF. nowadays MF means megafared.

but aside from that minor detail, I think I'll build one, it looks like loads of fun. does it proccess the sound to where you could hook it right up to a speaker?

drab (author)2007-04-04

do you know a good bgeinner's guide on the net for learning how to read schematics etc?

Botfly (author)2007-03-21

Stereo Microphone Techniques ( is a decent article with an explanation of popular microphone configurations (x/y 90 degress, ORTF, a/b), when to use them and photos.

llaven (author)Botfly2007-03-21

Thanks Botfly for the links are greats!!

Doingstuff (CRO) (author)2007-02-17

nice pics

royalestel (author)2007-02-15

Where is the second transistor on your schematic? And what is that "Electrec" on the left of the schematic? I'm Trying to make my own amp, so that would be really useful to know.

llaven (author)royalestel2007-02-15

the circuits is for one channel repeat the circuit for the other one.

The "Electrec" the correct name is Electret (sorry) that is a Microphone preamplifier with FET transistor internally and require a source voltage (on the schematic supply with the 1k resistor).

For more information about Electret mics:

royalestel (author)llaven2007-02-16

Thanks very much. I figured it out an hour or so after I asked. This is a very nice, simple amp!

thearchitect (author)2006-12-02

Your city sound recording is astonishing. I have a MZR900 and even using powered Sony mics, I can't get that life-like sound you have. Do you re-process the sound? Are you interested in digital upload capable new Minidisc recorder from Sony? Nice project, good instructable. Thanks!

llaven (author)thearchitect2006-12-02

The sound examples and anyone dont have a process only push REC bottom of my Minidisc, the second hand i dont use Sony stage software because i use Linux, so i use Audacity for "capture" the sound, i think the good result with this cheap mics is the effect Stereo the space between Right and Left mics is about 20 cms (like the space between us ears). Thanks for the comment

xenobiologista (author)llaven2007-02-04


thearchitect (author)llaven2006-12-04

Now I get it! :-) My Sony stereo microphones shouldn't be more than an inch apart. That's why yours make a difference!.. Cool!

Mr.Devious (author)2007-01-18

Alrighto pedro

Elastometer (author)2006-12-05

Excellent sound from such a very basic circuit with minimum decoupling. Do you have the S/N figures for the circuit?

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