Rechargable Pocket Sized Amplifier




About: Robots and video games...

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

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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.

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    300 Discussions


    2 years ago

    another best pocket size amp here


    3 years ago

    i used bc327, 2n3904, the same resistors and a 3w 8ohm speaker.It sounds loud and great. Thank you so much!

    2 replies

    3 years ago

    can we use tda2822 ic ?
    with li ion 3.7v battery?


    3 years ago

    and also a buzzing sound comes


    3 years ago

    it works but does not amplifies the sound very much. what should i do?


    4 years ago on Step 7

    chabon te quedo muy piola para ser de carton (otro argentino)
    nececito aprender a armar circuitos simples, y a leerlos del papel, tenes alguna recomendacion? algun tutorial o guia?
    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 :) )

    Hi, i am unfamiliar with electronics so i have some enquires. Which connections are joined to the "IN" section? The left, right or ground of the input jack?

    1 reply

    The left node of the "IN" bit connects to the "tip" 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.


    6 years ago on Introduction

    i make this amp, but using bc547 and bc557, bc 547 is good but 557 geted to hot,...
    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

    1 reply

    Reply 4 years ago on Introduction

    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.


    4 years ago on Introduction

    I made this amplifier using 2N3904 and 2N3906. It is working well but 2N3906 gets heated. Can you explain please?


    5 years ago

    thank for your posting i will try it


    5 years ago on Step 3

    All I get is a high pitched buzzing sound from my speaker once I connect the power. Please help???


    Bruno, podría usar dos de estos en unos audifonos? compré unos audifonos chinos y querría meterle dos circuitos de entros internamente.. podría? los Speakers son de 32 - 35 Ohm según el multimetro


    6 years ago on Introduction

    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?

    1 reply

    7 years ago on Step 3

    great ible *5

    Can I hook up 5 big speakers to this amplifier?