For low power amplifiers we could use integrated circuits like TDA family. But I will show how to make amplifier using operational amplifier. This amplifier is only to proof the concept. It real use can be as preamp for guitar or something like that.
I am not hold responsible for any damage that occurred during reproduction.
Step 1: Parts and Materials
- two 47 kΩ resistors, 1 kΩ resistor, 100 kΩ trimmer and 10 kΩ trimmer
- three 10 μF capacitors and 100 μF capacitor
- 9 V battery with wires or PSU with 9V output
- cable with 3,5 mm audio jack
- small speaker
- breadboard and wires
- pliers and tweezers
For testing you can use MP3 player, computer, mobile phone or any other device with audio output.
Step 2: Schematics
Trimmer P1 is for adjusting input power. P1 is not necessary. Capacitor C1 is for filtering DC current out from audio signal. With resistors R1 and R2 we set voltage divider. With voltage divider we set working point of amplifier to half of the supplied voltage (4,5 V in this case). Resistor R3 and trimmer P2 are there to set amplifiers gain. Capacitor C3 is output capacitor and it is for filtering output frequency (low cut).
Step 3: Assembly on Breadboard
Step 4: Testing
Step 5: Conclusion
Have fun building and using this amplifier!