D718 B688 Powerful Amplifier DIY Homemade

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I am showing in this video, how to make an ultra bass 100 watts mono class-AB powerful amplifier using d718 b688 & 2n3904 transistors. Combination of d718 b688 powerful amplifier is widely used for high gain. You must use transistor insulation (Mica) to prevent touching heat sink to avoid short circuit because both transistor are using opposite current.

I have chosen this circuit with very few components which is quite easy to assemble for beginners and students. I strongly recommend to choose large enough and thick heat sink for enough heat dissipation for safety of both transistors. The components list is also provided at the end of this article which is easy to find in the local market.

Circuit Diagram

Following is the Circuit Diagram of D718 B688 Powerful Amplifier with Volume Bass and Treble.

D718 B688 Powerful Amplifier Circuit Diagram

Development Images

of D718 B688 Powerful Amplifier DIY

Step # 1

Tighten D718 & B688 transistors on to the heat sink with proper insulation (MICA). Be sure the back plate of both the transistors should not be touched with heat sink. Join plus & minus sides of the two diodes 1N4007 together. Solder one positive end of right diode with Base Pin.1 of right transistor B688. And other negative of left diode with Base Pin.1 of left transistor D718. Connect two 0.33 ohms/5w resistors to Emitters Pin.3 of both transistors. Join the other ends of both transistors together.


Step # 2

Solder the Collector of 2N3904 Transistor to the Bass of B688 and Emitter of 2N3904 Transistor to Collector of B688. Also solder a 100k resistor to the base of 2N3904 Transistor and the center joint of 0.33 ohms/5w resistor.

D718 B688 Powerful Amplifier Images1

Step # 3

Connect negative side of 4.7uf capacitor to the base of 2N3904 Transistor.

D718 B688 Powerful Amplifier Images2

Step # 4

Solder negative end of 2200uf/50v capacitor to the center joint of two 0.33 ohms resisters. Also solder 1k resister’s one end to the base of D718 and the other end to the positive side of 2200uf/50v capacitor.

D718 B688 Powerful Amplifier Image3

Step # 5

I did not show the working of bass-treble circuit here. For more detail to see bass-treble [Click Here]. Connect the positive pin of 4.7uf capacitor to Center Pin.2 of volume control.

D718 B688 Powerful Amplifier Image4

Step # 6

Take one 0.47 ohms/5w resister and also take 0.6mm copper enameled wire. Wrap the around the resister 12 times and solder both ends with both ends of resister.

D718 B688 Powerful Amplifier Image5

Step # 7

Now solder one end of resister coil to the collector Pin.2 of D718 transistor. Attach red positive wire of power supply to center pin Collector of D718 transistor and black negative wire of power supply to center pin Collector of B688 transistor.


Step # 8

Its time to attach 3.5mm mobile jack. Solder the both left & right audio output wires to Pin.1 of Bass Controller and ground wire to Pin.3 of volume controller. Also Join Pin.3 of Volume Controller Collector, center pin of B688 transistor which is ground.


Step # 9

Connect Speaker’s positive to the resister coil’s empty end. Speaker’s negative will go to +ve connection of the 2200Uf Capacitor.


Connect the jack pin to mobile. Turn the power supply On, play music with mobile and Enjoy. Thank you so much for visiting this site.

List of Components

used in D718 B688 Powerful Amplifier

  • D718 Transistor x 1
  • B688 Transistor x 1
  • 2N3904 Transistor x 1
  • 1N4007 Diode x 2
  • 2200uf Capacitor x 1
  • 4.7uf Capacitor x 1
  • 104 Capacitor x 4
  • 0.33 Ohms Resistor x 2
  • 1k Ohms Resistor x 3
  • 2.2k Ohms Resistor x 2
  • 100k Resistor x 1
  • 50 Potentiometer x 3
  • Heat Sink x 1
  • Power Supply Socket (Optional)
  • 3.5mm Mobile Jack (Optional)
  • Power Supply 12v
  • Speaker 4 Ohms

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14 comments on D718 B688 Powerful Amplifier DIY Homemade

  1. I have tis amplifier can I replace the power transistors with MOSFET to use 40-040 8 amp transformer.

  2. In your write up step 9, you incorrectly state that the negative of the speaker goes to Ground.

    Step # 9
    Connect Speaker’s positive to the resister coil’s empty end. Speaker’s negative will go to ground

    That is incorrect and just releases the magic smoke from the speaker. The -ve speaker connection is to the +ve connection of the 2200Uf Capacitor which you correctly show in the video and the schematic.

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