Maker Factory ELECTRONICS EXPERIMENTS BOX Manual page 162

Circuit 138: output circuit mixing console
Setup information
Install the two transistors, the two electrolytic capacitors and the five resistors as shown in Fig. 2.138 The
seven jumper wires come next. Finally 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
If everything is wired correctly, you can safely go ahead and connect an mp3 player. You will hear your
music full volume coming from the Piezo element. The special feature in our circuit here is that together
with the previous experiment, we have got all the basic modules for an NF mixer. If each one gets a poten-
tiometer connected to the input, we would have a handy NF mixer. You have already learned about the
preliminary stage for such a mixer in the previous experiment.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.138.
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Components required:
2 x 2N3904 transistors,
1 x 220 Ω resistor, 1 x 1 kΩ
resistor, 1 x 47 kΩ resistor,
1 x 220 kΩ resistor,
1 x 1 MΩ resistor,
1 x 1 μF electrolytic capaci-
tor, 1 x 10 μF electrolytic
capacitor, 1 x Piezo ele-
ment, 1 x breadboard,
1 x 9V battery with clip
connector
Fig. 2.138: output circuit mixing
console