In this video i am showing, how to make a dual transistors diy d718 d882 amplifier. The circuit uses minimum components to be built easily by beginners. The volume control (potentiometer) very well work in its full range. The transistor heats up on 12 volts power supply. You must use a large and heavy heat sink for proper heat dissipation of the transistor. Otherwise transistor will not survive and will burn on long time run. Use well filtered power supply for clear sound. I personally recommend that you use 6800uf / 50 volts capacitor.
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Following image has a circuit diagram of the above project. I used here one d718 power transistor in power stage and one d882 transistor in pre-amp.
These are the basic components used in this project. One D718 NPN transistor, one D882 NPN transistor, one 39k resister, one 220uf electrolytic capacitor of 50 volts, one 2200uf electrolytic capacitor of 50 volts and one single pole 10k potentiometer used for volume controller.
At very first, take D718 transistor use thermal paste on the base. It will provide better connectivity with heat sink.
After using thermal paste, stick the transistor onto the heat sink directly and well tighten with screw. You can use mica underneath the transistor for separating it with the heat sink. I am not using it because no other transistor will be used to stick with the heat sink. If you are also connecting it directly then any voltage will run through collector, it will pass to heat sink. Then be careful, the negative voltage should not touch with the heat sink.
Now take one D882 transistor and solder its pin-1 with D718 pin-1 & pin-2 of D882 transistor to pin-2 of D718 transistor respectively as shown in the following image.
Now take 2200uf 50 volts electrolytic capacitor and solder its positive leg with the center pin (collector) of D718 transistor for output to the speaker.
Now take one 220uf electrolytic capacitor of 50 volts and solder its positive leg to pin-3 (base) of D882 transistor. And the negative leg of the capacitor to the center pin-2 of 10k potentiometer.
Solder one leg of 39k resister to center pin-2 (collector) of D718 transistor. And the other leg of 39k resister to pin-3 (collector) of D718 transistor.
Take a piece of wire and solder its one end to pin-3 (emitter) of D718 transistor. And the other end of piece of wire to pin-1 (GND) of 10k potentiometer.
This is 3.5mm mobile jack which will be used to provide audio input from mobile or any source to amplifier.
Solder the GND wire to pin-1 (GND) of 10k potentiometer and both two wires or one of them to pin-3 of potentiometer.
Take two piece of wires for speaker connections. Solder one to pin-3 (emitter) of D718 transistor for GND. And solder the other wire to 2200uf capacitor’s negative leg. You can directly connect speaker wires here instead of using separate piece of two wires.
Now take a 12 volts power socket and solder its red positive wire to center pin-2 (collector) of D718 transistor. And back negative wire to right pin-3 of D718 transistor for 12 volts power input. Instead of using this power socket, you can directly solder here the wires of power supply.
Here in the following image I am showing the voltage of the power supply which I will used to run this amplifier. I using pc power supply of 5 amps for demonstration.
Below image shows the final finished product in action. Fore more detail play video at top of this article and enjoy the project.
List of Components
used in DIY D718 D882 amplifier
- D718 Transistor x 1
- D882 Transistor x 1
- 2200uf 50v Capacitor x 1
- 220uf 50v Capacitor x 1
- 39k Resister x 2
- 10k Potentiometer x 1
- Heat Sink (Large enough and thick)
- 4 Ohms Speaker
- 12 volts Single Power Supply
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