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
A piece of 3mm cardboard
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
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
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
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
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
Just connect a wire betwen the amplifier and the source of sound.
Step 7: Finished
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.