In this instructable I gonna try to describe how to make a simple rechargable pocket sized amplifier.
It's works using only two low power transistors and two nickel metal hydride batteries (Ni / MH).
The case is made with 3mm cardboard for making it as light as posible.
Ps: I'm from Argentina so let me know for any grammar mistake

Step 1: Materials

For the case:
A piece of 3mm cardboard
A cutter
Some glue

For the circuit:
R1= 4k7 resisor ( yellow violet red)
R2= 1M resistor (brown black green)
Q1= BC548 or 2N3904
Q2=BC327 or 2N3906
C1= 10uF capacitor
2 AAA batteries

A batteries charger
A wire for connecting the amplifier to the sound source
A wire for connecting the amplifier to its charger

Step 2: Making the Case

Cut off 6 sheets of cardboard.
2 squares of 46mm x 90mm
2 squares of 90mm x 24mm
2 squares of 24mm x 40mm

Put them together with tape and paste with some glue.
When the glue be dry take off the tape.
I used a big piece of black paper for a better look.
You need to paste the black paper all arround the case like in the picture.

Step 3: Making the Circuit

Is a really easy to do circuit.
First of all you gonna need to do the PCB.
You can do it with ironing method using the pdf or using the way that you allways use.
The PCB is designed for the BC transistors so if you what to use the 2n3904 and 2n3906 transistor be careful whith the terminals.

R1: 4k7 resisor ( yellow violet red)
R2: 1M resistor (brown black green)
Q1:  BC548 or 2N3904
Q2: BC327 or 2N3906
C1: 10uF capacitor

Amplifier circuit extracted from "Lupin, introduccion a la electronica".

Step 4: The Switch

The switch selects betwen the on mode and the charging mode (off).

If you won't make it rechargable and you will use common batteries just use a normal on/off switch.

Step 5: The Charging Position

Actually the charging mode is no really needed but is really usefull because you don't need to disassemble the system for charging the batteries.
You gonna need to make a wire for connecting the charger to the amplifier.
This wire is really easy to do.
In one side use two crocodile clips for connecting to the charger( you could solder this terminals directly to the charger if you gonna use the charger just for this amplifier) and in the other side a jack for the plug that you chose for the charging position.

Step 6: The Audio Position

When the switch is in the audio position the system is ready for amplify.
Just connect a wire betwen the amplifier and the source of sound.

Step 7: Finished

That's all.
For a stereo system you need to do one of these for each chanels.
The audio output is not enough for giving a party but is enough for sharing your music with your friends.

<p>another best pocket size amp here </p><p>https://www.youtube.com/watch?v=K7Tt0qS5aQo</p>
<p>i used bc327, 2n3904, the same resistors and a 3w 8ohm speaker.It sounds loud and great. Thank you so much!</p>
Can I see the circuit that you've done?
I am looking for an alternative transistor for this
can we use tda2822 ic ?<br>with li ion 3.7v battery?
<p>and also a buzzing sound comes</p>
<p>it works but does not amplifies the sound very much. what should i do?</p>
<p>chabon te quedo muy piola para ser de carton (otro argentino)<br>nececito aprender a armar circuitos simples, y a leerlos del papel, tenes alguna recomendacion? algun tutorial o guia?<br>el amplificador te quedo muy bueno, yo quiero hacer un amplificador sin parlante para poder unir mucho parlantes (y asi conquistar el mundo, pero no viene a tema :) )</p>
Hi, i am unfamiliar with electronics so i have some enquires. Which connections are joined to the &quot;IN&quot; section? The left, right or ground of the input jack?
<p>The left node of the &quot;IN&quot; bit connects to the &quot;tip&quot; part of the input socket and the right node connects to the sleeve of the input socket (which is always ground). If you have a stereo socket, this circuit will only amplify one channel of it.</p>
i make this amp, but using bc547 and bc557, bc 547 is good but 557 geted to hot,... <br>i ll try to make one with your transistor, for now its working but not as yours, i lll use your components and see next
<p>Did the 557 burn out, or did it just get hot to the touch? Interested, because I have a 557 on me and am thinking of giving it a go. Otherwise I'll wait for the 2N series to come in.</p>
<p>I made this amplifier using 2N3904 and 2N3906. It is working well but 2N3906 gets heated. Can you explain please? </p>
thank for your posting i will try it
All I get is a high pitched buzzing sound from my speaker once I connect the power. Please help???
Bruno, podr&iacute;a usar dos de estos en unos audifonos? compr&eacute; unos audifonos chinos y querr&iacute;a meterle dos circuitos de entros internamente.. podr&iacute;a? los Speakers son de 32 - 35 Ohm seg&uacute;n el multimetro
I have a question about the amp circuit. I was goofing around with it, and I noticed nothing different when I removed the 1M resistor. What is that resistor supposed to do?
Also, where would I put a volume control resistor in this circuit?
great ible *5<br><br>Can I hook up 5 big speakers to this amplifier?
in paralel probably
That's like getting a dog and asking if it can pull 5 plows.
the sound from mine is just a buzzing sound
i have made this and getting high distortion noise .....where have i did wrong ? <br>instead 3V i m using 9V battery and transistor BC328 in place of 327 , else everything is same . <br>
You should try using two AA or AAA batteries as suggested, because you are probably over-driving the transistors.
You should put the volume on the device on low and make sure all the input connects are wired strong and not touching.
all inputs are tight and i m not getting enough sound in low volume ...and high distortion at high volume . <br>
If this is the case then either your speakers are in bad shape like my first pair or your battery is low on power so its not supply much of a voltage. If you don't mind can you try to post a picture of the speakers. If nothing else it must probably be the transistor that's the distortion.
If I up the size of the transistors can I drive 4ohm speekers?
I built this little amp and it works great considering its simplicity and low voltage. It drives cell phone speakers especially well. <br>Would it be possible to use a more robust set of transistors and higher uf caps and increase the voltage? Maybe drive a little bigger of a speaker.
How exactly do you make the PCB, understand you need to print the PDF, but what exactly do you do.
I was wondering if there is a way to make this with a 1/4&quot; input jack for electric guitars. Would make a great portable amp.
How 'bout just adding a 1/4 jack and trying it out? <br><br>Dunno about the input impedance...But try it :P<br><br>If you are smart you might wanna build something like: <br>http://runoffgroove.com/littlegem.html<br><br>Easy as pie<br><br>or<br><br>http://www.beavisaudio.com/projects/NoisyCricket/<br><br> Better version ! :P Props to Dano the designer.<br><br>These are all based upon the allmighty Smokey amp.<br>Maybe you should just buy one of those ;)
<a href="http://driph.com/words/wp-content/uploads/2008/04/e.gif" rel="nofollow">Thanks for that, the little gem is pretty much exactly what I needed.</a>
but they need ic this dosent<br>so i prefer this one
Then please, tell me what is wrong with using a IC?<br><br>OP-Amps circuit mostly use IC's for the bigger gain they can deliver. <br><br>LM386 is the most used audio amplifier in DIY and guitar effects. <br>Its reliable, sounds good and is easy to work with.( As in one chip and two capacitators is the bare minimum for a working guitar amp. eg Smokey amp by Zinky electronics)<br><br>So please don't give your opinion.
Sometimes it's easier to obtain some components such as transistors and capacitors, whereas specific ICs have to be purchased. I for one will be building this as opposed to one of the better ones which use an IC for that very reason, I'm on a very low budget and have these components (or similar once which will suffice) to hand. Just so you know you've brought an extra member to Instructables. I was looking for a schematic for a simple push pull audio amplifier when I found this one, and on reading your comment and finding it so rude I thought I'd sign up and give my reasons for wanting a simple amp as opposed to one that would require me to purchase anything.
Wonderful world we live in, when people are shunned from giving their opinion by some guy who... I don't even know what you do. Great job.<br><br>The misspelled word of the day is:<br>Mispell
Not asking, commenting he is sooooo cute!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!<br>!
Do I.C. Mr Resistor?
That's an interesting way of creating a project box. Usually someone would get some sort of plastic container and paint it, but you use a kind of cardboard wood and instead of paint, you use paper.
some pics
Had to ask!<br>On your strip board, why did you put your components so far from each other?<br>They won't bite each other!!
i know but i had of this size and that time i was not knowing how to cut a strip board
You use a sharp stanley knife (thats what we call them in the UK but I've seen them called box cutters on here?!) anyway you just score it with the knife then snap it.
what is the capacitor voltage? i don't think a 35V 10 uF one would do right
yes, it would work, it is just have a bigger size but it will do fine.
but will it act exactly the same?
yes it will
What kind of speaker did you use? It looks like a computer speaker. Would any speaker work?

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