Headphone Amplifier - Maker Factory ELECTRONICS EXPERIMENTS BOX Manual

2.75 Headphone amplifier

Circuit 157: Headphone amplifier with Piezo element
Setup information
Install the two transistors, the six resistors and the four electrolytic capacitors as shown in Fig. 2.157. The
twelve jumper wires come next. Last but not least connect the Piezo element. Check the placement on the
board again and only then connect the battery.
You can significantly increase the sensitivity of the Piezo element by using a sound plate or even a sound
box. Read more about it in Chap. 1.2.3
Experiment
Even if everything is wired correctly, nothing will happen at first. If you connect an mp3 player to the input,
you will hear the music blasting from the Piezo element. This little circuit is very useful in various DIY pro-
jects.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.157.
182
Components required:
2 x 2N3904 transistors,
1 x 1 kΩ resistor,
1 x 2.2 kΩ resistor,
1 x 10 kΩ resistor,
1 x 22 kΩ resistor,
2 x 100 kΩ resistors,
1 x 1 μF electrolytic
capacitor, 2 x 10 μF
electrolytic capacitors,
1 x 100 μF electrolytic
capacitor, 1 x Piezo ele-
ment, 1 x breadboard,
1 x 9V battery with clip
connector
Fig. 2.157: Headphone ampli-
fier with Piezo element