150-Watt BJT (Bipolar Junction Transistor) Stereo Power Amplifier

If you want to learn more about electronics and at the same time build something useful and enjoyable, making your own audio amplifier is a great project to try. Audio amplifiers are used to make weak sound signals stronger so speakers can produce louder and clearer sound. They are commonly found in home sound systems, karaoke setups, speaker boxes, and many other audio devices. By building your own amplifier, you will not only understand how these systems work, but you will also gain hands-on experience in soldering, wiring, troubleshooting, and circuit assembly.

In this project, we will show you how we designed and assembled our own 150-Watt Stereo Power Amplifier using TIP3055 and TIP2955 power transistors. Instead of buying a ready-made amplifier, we decided to create one ourselves so we could learn the actual process of building and testing an audio amplifier circuit. This project is also a good way for beginners and students to improve their practical electronics skills while creating a working device that can actually be used for speakers and sound systems.

While working on this project, we used different resources to help us complete the amplifier successfully. We searched on the internet to learn about amplifier circuits, component functions, and proper wiring techniques. We also used AI to help us understand concepts, organize ideas, and improve our documentation. Most importantly, our professor guided us throughout the project by teaching us the proper procedures, safety precautions, and correct methods in assembling and testing the amplifier circuit.

In this guide, we will teach you step-by-step how to build the amplifier, from creating the schematic diagram up to testing the final output. We will also share some important tips and precautions to help you avoid common mistakes during assembly. Even if you are still a beginner in electronics, this project is a great way to start learning because it combines both theory and hands-on experience.

By the end of this project, you will not only have a functional stereo power amplifier, but you will also gain a better understanding of how amplifier circuits work and how different electronic components contribute to sound amplification. With enough patience, proper guidance, and willingness to learn, you can successfully build your own amplifier and improve your skills in electronics at the same time.

PCB Components

Resistors (ratings):

1. 100 Ω (6 pcs.)
2. 330 Ω (4 pcs.)
3. 4.6k Ω (2 pcs.)
4. 2k Ω (2 pcs.)
5. 1k Ω (2 pcs.)
6. 30k Ω (4 pcs.)
7. 10k Ω (2 pcs.)
8. 560 Ω (4 pcs.)
9. 100k Ω (2 pcs.)
10. 0.5 Ω, 5W ceramic cement resistor (2 pcs.)

Diode:

1. Zener diode (8 pcs.)

Transistors:

1. TIP2955 (2 pcs.)
2. TIP3055 (2 pcs.)
3. BD140 (2 pcs.)
4. BD139 (2 pcs.)
5. C2001 (2 pcs.)
6. A733 (16 pcs.)

Capacitors:

1. 47μF 50V (8 pcs.)
2. 2A1045 - Mylar capacitor (2 pcs.)
3. 100pF Ceramic capacitor

VCC → Filters:

1. Transformer 220V → 20V AC
2. GPBC3510 (Bridge rectifier)
3. 10,000μF 50V capacitor (2 pcs.)

External:

1. Speaker terminals (2 pcs.)
2. RCA jacks (2 pairs)
3. Push button (1 pc.)

Audio Control:

1. Dual potentiometer
2. For volume: 60k Ω
3. For treble: 50k Ω
4. For bass: 50k Ω
5. Single potentiometer
6. For balance: 100k Ω
7. 104 ceramic capacitors (8 pcs.)
8. 2.2k Ω resistor (2pcs.)
9. 1k Ω resistor (2 pcs.)

TOOLS:

1. Soldering Iron
2. Ferric Chloride (FeCL3) Liquid
3. Soldering Lead
4. Photoresist PCB
5. Connecting Wires
6. Screws
7. Mini Drill
8. Bluetooth Module

The first thing you need to do is create or study the schematic diagram of the amplifier. The schematic serves as the guide for all component connections and helps you understand how the circuit works.

In our design, we used:

1. TIP3055 and TIP2955 as the power transistors
2. BD139 and BD140 as the driver transistors
3. Resistors and capacitors for stability and signal control

Before proceeding, carefully check the schematic to avoid connection errors during assembly.

After finalizing the schematic, design the PCB layout based on the circuit diagram. Arrange the components properly to make the circuit organized and compact.

When designing the PCB:

1. Minimize overlapping tracks
2. Provide enough spacing between components
3. Place larger components like transistors and capacitors properly
4. Allocate space for heatsinks and external terminals

A proper PCB design improves the appearance, reliability, and performance of the amplifier.

Gather all the required materials, components, and tools needed for the project.

Materials Needed

1. TIP3055 and TIP2955 transistors
2. BD139 and BD140 transistors
3. Resistors
4. Capacitors
5. PCB board
6. Transformer or power supply
7. Heatsink
8. Speaker terminals
9. Audio input jack
10. Wires

Tools Needed

1. Soldering Iron
2. Ferric Chloride (FeCL3) Liquid
3. Soldering Lead
4. Photoresist PCB
5. Connecting Wires
6. Screws
7. Mini Drill
8. Bluetooth Module

Before using the components, test them first using a multimeter to ensure they are functioning properly and are not damaged.

Once the PCB layout is completed, print the PCB design using a laser printer onto glossy paper or transfer paper.

The laser-printed design will later be transferred onto the copper-clad board during the PCB fabrication process.

Make sure:

1. The print is dark and clear
2. The PCB size is accurate
3. The tracks are properly aligned

1. Transfer the laser-printed PCB design onto the copper-clad PCB using a transparent sticker to ensure that the circuit layout is properly attached to the board.
2. Prepare the Ferric Chloride solution carefully in a plastic container. Make sure to wear protective gloves and work in a safe and well-ventilated area.
3. Submerge the PCB into the Ferric Chloride solution for about 20 minutes or until the unwanted copper is completely removed, leaving only the desired PCB traces.
4. After the unwanted copper has been removed, carefully take out the PCB and wash it thoroughly with clean water. Avoid direct contact with the chemical by using tweezers or a similar tool when handling the PCB.
5. Once the PCB is clean and dry, drill holes using 1mm bit to 1.5 mm bit for transistors on the designated areas for proper placement of the electronic components.

This process leaves only the desired copper traces for the amplifier circuit.

Place the electronic components onto the PCB according to the schematic and PCB layout.

Start with the smaller components first:

1. Resistors
2. Diodes
3. Small capacitors

Then proceed with:

1. Driver transistors
2. Large capacitors
3. Connectors
4. Power transistors

While soldering:

1. Make clean solder joints
2. Avoid solder bridges
3. Observe proper polarity and orientation

Mount the TIP3055 and TIP2955 transistors onto the heatsink using thermal paste for proper cooling.

After soldering all components, inspect the PCB carefully.

Use a multimeter to:

1. Check continuity
2. Detect short circuits
3. Verify power connections

Before applying full power, double-check all wiring and component orientations to avoid damaging the amplifier circuit.

Design and create a casing for the amplifier to protect the circuit and improve its appearance.

When making the casing:

1. Provide ventilation holes for airflow
2. Allocate space for the heatsink
3. Ensure easy access to the controls and connectors

The casing also improves safety and durability.

Install the external components into the casing, including:

1. Power switch
2. Volume control
3. Audio input jack
4. Speaker terminals
5. Power connector

Secure all wirings properly to avoid loose connections during operation.

Finally, connect the amplifier to a power supply, audio source, and speakers for testing.

During testing:

1. Start with low volume
2. Check if both channels are working
3. Listen for distortion or noise
4. Monitor the heatsink temperature

If the amplifier produces clear stereo sound and operates properly without overheating, then the project is successful and ready for use.