This is 120W power amplifier schematic using TO-3 package complementary transistors, NPN and PNP polarity. The well-known power transistor pair of 2N3055 and MJ2955 used in this circuit. +/- 50V symmetrical (split/dual polarity) power supply with minimum 3A electric current should be used for maximum performance.
120W Power Amplifier Part List
Transistors
- 2N3055 (substitution: MJ15003 or 2N3772) : 2
- MJ2955 (substitution: MJ15004 or 2N3771) : 2
- TIP42 : 2
- TIP41 : 1
- 2SC2229 or 2SC2230 or C1573 : 2
- A1015 or A872 or A733 : 2
Capacitors
- 100uF/50V electrolytic capacitor: 2
- 470nF (474) nonpolar polyester capacitor: 1
- 100pF (101) nonpolar ceramic capacitor : 2
- 470pF (471) nonpolar ceramic capacitor : 2
- 10pF nonpolar ceramic capacitor : 2
- 100nF (104) 100V nonpolar polyester capacitor : 2
Resistors
- 0.33 Ω (5W) : 4
- 10 Ω to (1W) – brown, black, black : 1
- 100 Ω (1W) – brown, black, brown : 2
- 33 Ω (1/4W) – orange, orange, black : 1
- 150 Ω (1/4W) – brown, green, brown : 3
- 10KΩ (1/4W) - brown, black, orange : 1
- 1KΩ (1/4W) - brown, black, red : 1
- 4.7KΩ (1W) - yellow, violet, red : 1
- 68KΩ (1/4W) - blue, gray, orange : 1
- 56KΩ (1/4W) - green, blue, orange : 1
- 33KΩ (1/4W) – orange, orange, orange : 1
- 3.3KΩ (1/4W) – orange, orange, red : 2
Diodes
- 3A Diode 1N5404 : 2
- 1A Diode 1N4007 : 3
- Zener diodes between 20 and 24 volts : 1
Others
- 3A fuse
- small 3-pin (GP) connector
- large 6-pin connector (Molex)
- aluminum heatsink
- potentiometer of 20K if you want to add volume control
120W Power Amplifier PCB Layout Design
Bottom PCB Layout (Copper)
Top PCB Layout and Component Placement
How to mount the transistors to the aluminium heatsink, see below image:
The points are: prevent circuit shortage, use proper isolator and use thermal compound for maximum heat spreading to the heatsink. Use mica between the transistor and the heatsink.
Power Supply Circuit for 120W Power Amplifier
Power Supply Bottom PCB Layout
Power Supply Top PCB Design
Power Supply Part List
- Transformer for the mono amplifier should be 35 + 35 volts AC with a minimum of 3 amps. If the stereo channel, the amperage should be doubled.
- Capacitors of 4700 uF/63V: 4
- Diode bridge (rectifier) ​​of 15 Amps: 1
120W Power Amplifier Wiring Connection
This is how to connect the amplifier module to the speaker, power supply and audio input. And connect the power supply module to the transformer.
How can I get the Gerber files for this project?
thank you
Is there schematic for the power supply and where to place the 3A fuse?
The PCB design shows two wires connection to GND from Top are they jumper wires or fuse connection?
Can I use 1N5408 instead on 1N5404 diode?
Dear Sir, I am interested in your 120 watt Audio Amplifier DIY above, in the schematic it shows 50v DC power supply, but in the instruction it require 35v dual supply, which one to use?
Can I replace the power, supply with ready made switching power supply of 35v not dual only plus and minus out put, no earth connection the reason I cant find transformer with 35v dual power supply, or too expensive and too heavy.
Thank you.
Your reply and help is very much appreciated.
I have build that circuit and its 100% working thanks alot….very smart and useful. Please send a circuit diagram 200 watts using MOSFETs
where to use 20k potentiometer your circuit
potentiometer of 20K if you want to add volume control
Read more http://circuitdiagram.net/120w-power-amplifier-power-supply.html
I am interested in 120watt amplifier, I want to assemble this circuit. I hope that I can manage it.
120W Power Amplifier pcb