In this video i am showing, how to make a very simple but powerful bass audio DIY D718 stereo amplifier homemade using two D718 transistors. This is a class-A amplifier with low efficiency. I am just demonstrating it for educational purpose. It is designed with minimum components for beginners or students. I do not recommend it for continuous professional use without modification or addition of pre-amplifier. I used 12 volts power supply to run this project. 4 ohms speakers of are recommended of any size for each side. Two speakers of 4 to 8 ohms can be joined together in parallel each side. If you are using more than 4 ohms then use two of them together in parallel connection which will reduce its resistance in half. But use them in both sides.
used in DIY D718 stereo amplifier
Following is the circuit diagram of dual D718 transistors stereo class-A amplifier. The circuit uses minimum components. So its very easy for beginners and students to build it. You can use 2 pieces of 560 to 1k ohms resister, 2 pieces of 100uf 50 volts electrolytic capacitor and a hand made coil of 150 to 200 turns with 26 awg copper enameled wire. Potentiometer is not shown or used in this circuit but you place one 50k potentiometer with its input source.
Stick the two transistors of D718 onto the heat sink with proper insulation (mica) and tighten it well. Take two 680 ohms to 1k resisters and connect them from base to collector in each transistor. Also take two 100uf/50v capacitors and connect their positive end to base of both transistors.
Take two tubes of 1″ length and wind 120 to 200 turns of 26 AWG copper enameled wire.
Place these coils on a board with hot glue and insert their one end of each coil to one end of each connectors for the speakers.
The other end of both the coils will be connected and soldered to the center pin.2 (collectors) of each D718 NPN transistors.
Take two piece of wires and connect / solder their one side to left most pin.1 (base) of each D718 transistor. And the other side of wires, solder them to the 3-pole input connector’s left and right sides.
Take a piece of red wire and connect from positive power supply connector to the positive side of speaker connectors.
Connect the negative point of power supply terminal to both the emitters of transistors together for ground. Also connect the center point of 3-pole input connector to the emitter of the transistor for ground.
Connect both speakers to their terminals. Connect power supply wires to its terminal and 3 wires of 3.5mm audio jack to input 3-pole connector. Turn the power ON and insert the audio jack into mobile. Now play the music and enjoy the project.
Lits of components
- D718 transistor x 2
- 100uf / 50v capacitor x 2
- 560 to 1k ohms resistor x 2
- Coil on 1″ tube 26 AWG / 150-200 turns x 2
- PVC connector 2-pole x 3 (optional)
- PVC connector 3-pole x 1 (optional)
- Heat sink large enough
- Power supply 12 volts
- Speakers 4 ohms
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