Replicating 150 W Stereo Power Amplifier

Cavite State University - Don Severino Delas Alas Campus

Bachelor of Science in Electronics and Communications Engineering

S.Y. 2025-2026

Subject Code & Name:

1. ECEN 70- Electronics 2

Members:

1. Concepcion, Jemaelah P.
2. Escorrido, Jose Danielle C.
3. Fronda, Adrian Von A.
4. Nuestro, Daniel Anthony C.
5. Romen, Jerick Ronn O.
6. Telmo, Ahron Tristan Jay B.

Year & Section:

1. BSECE 2-2

Instructor:

1. Dr. Edwin R. Arboleda

We are Electronics and Communications Engineering (ECE) students from Cavite State University–Don Severino Delas Alas Campus in Indang, Cavite, Philippines. In this project, we are replicating a 150-Watt Stereo Active Power Amplifier with Knob Panel, a Class AB stereo amplifier integrated with a power supply unit (PSU) and control knob panels.

The amplifier is powered by an 18V input supplied to the PSU, which then distributes the regulated power to the control knob panels and the two amplifier channels for stereo output. The audio input signal is combined with the power from the PSU and is then amplified through the Class AB amplifier stages. This configuration merges the high-fidelity characteristics of Class A operation with the high efficiency of Class B operation, resulting in balanced and efficient audio amplification. It is a commonly used design in home audio amplifier systems.

The system includes four control knobs: bass, which adjusts low-frequency response for deeper and heavier sound; treble, which controls high-frequency response for sharper and brighter tones; balance, which adjusts the relative volume between the left and right speakers; and volume, which controls the overall output loudness of the system.

The main objective of this project is to design and replicate the stereo amplifier based on an available online kit. This includes creating the schematic diagram and printed circuit board (PCB) layout of the amplifier. Most importantly, the project aims to ensure that the amplifier functions properly and delivers accurate and efficient audio amplification.

Materials and Tools Needed:

1. Soldering Iron
2. Soldering Lead
3. Soldering Pump
4. Soldering Flux
5. Extra Components (for spare parts)
6. Copper Clad Board
7. Ferric Chloride (for etching)
8. Etching Tray
9. Chassis Box (DIY)
10. 2x Speakers
11. Connecting Wires
12. Audio Cable Jack
13. Utility Knife
14. Wire Cutter
15. Laptop (for schematics)
16. Smartphone (with audio port)
17. Breadboard
18. Multimeter
19. Transformer
20. Drill

For the components we used:

TRANSISTORS:

1. 2x TIP2955 transistors
2. 2x TIP3055 transistors
3. 2x BD139 transistors
4. 2x BD140 transistors
5. 8x 2SC945 transistors
6. 2x 2SA733 transistors

DIODES:

1. 4x rectifier diodes
2. 4x small signal diodes (1N4148)
3. 1x LED diode

CAPACITORS:

1. 2x 3300 μF electrolytic capacitors
2. 3x 470 μF electrolytic capacitors
3. 6x 1 μF electrolytic capacitors
4. 4x 100 pF ceramic capacitors
5. 2x 100 nF mylar capacitors
6. 2x 22 nF mylar capacitors
7. 2x 10 nF mylar capacitors
8. 2x 4.7 nF mylar capacitors

RESISTORS:

1. 4x 0.47 Ω, 5W ceramic cement resistors
2. 6x 2.2 kΩ resistors
3. 4x 1 kΩ resistors
4. 4x 10 kΩ resistors
5. 2x 330 Ω resistors
6. 2x 15 kΩ resistors
7. 2x 220 Ω resistors
8. 2x 100 kΩ resistors
9. 2x 5.6 kΩ resistors
10. 2x 100 Ω resistors
11. 2x 150 Ω resistors
12. 2x 1 MΩ resistors
13. 2x 2.7 kΩ resistors
14. 2x 560 Ω resistors
15. 2x 5.6 kΩ resistors
16. 2x 3.9 kΩ resistors

POTENTIOMETERS:

1. 3x 6-pin 50 kΩ potentiometers (Bass, Treble, Volume)
2. 1x 3-pin 100 kΩ potentiometer (Balance)

In order to replicate our desired stereo amplifier, we first searched for existing stereo amplifier kits and DIY amplifier circuits available online. By studying the amplifier boards, components, and circuit configurations shown in the videos, we were able to identify the important parts responsible for audio amplification and sound output.

Here are the links for our desired amplifier:

1. https://www.youtube.com/watch?v=AZn_0NnOVSE
2. https://www.youtube.com/watch?v=Zc_i6GVhHIs
3. https://www.youtube.com/watch?v=JXhjIgrpwM8

Once we have selected our desired stereo amplifier kit, the next step is to carefully analyze all its components. This includes identifying each part’s position in the circuit and documenting its specifications, especially the values and part numbers of key components such as transistors. It is also important to study how each component is connected within the circuit, since understanding these relationships is essential when recreating the design in NI Multisim.

NI Multisim is an electronic simulation software widely used by electrical and electronics engineers and technicians. It allows users to build and simulate circuit schematics before actual hardware implementation, making it a valuable tool for design verification and troubleshooting.

As shown in the schematic above, we can see the complete layout of the desired stereo amplifier. For beginners, a practical approach is to place components in Multisim according to their physical arrangement in the amplifier kit. After placing the components, each one should be connected step by step, following the original circuit connections carefully to avoid errors.

Once the schematic is completed, the circuit can be simulated to verify its performance. Using virtual instruments such as an oscilloscope, you can check whether the amplifier is properly increasing the signal amplitude as expected. This step is important to ensure that the design functions correctly before moving on to PCB development.

Note: In cases where certain components are not available in NI Multisim, alternative parts may be used. However, it is important to ensure that these substitutes closely match the characteristics and behavior of the original components so that the overall circuit performance remains accurate and reliable.

Once we had determined all the components, we proceeded to purchase everything we needed based on the schematics we had prepared. We made sure to gather all the required electronic parts for the circuit, along with the materials needed for fabricating the PCB, including the copper board and ferric chloride. We also acquired the necessary soldering tools and other electronic paraphernalia to complete the assembly. In addition, we utilized the tools available to us, such as drills and other equipment, to support the construction process.

After we buy our materials and components, we proceeded to design and create our own Printed Circuit Board (PCB) by replicating the PCB layout we found online. We used the existing PCB as our reference because it already contains the proper arrangement of components and circuit connections needed for the stereo amplifier to function correctly. However, instead of directly copying the entire design, we customized the PCB layout to include our names etched onto the board, as shown in the image above. This customization not only personalizes our project but also demonstrates our involvement in the PCB design process.

This step is very significant because the PCB layout serves as the main guide during the etching process. It ensures that the copper traces are accurately formed and that all electronic components will be connected properly according to the circuit design.

After completing the PCB layout design, we proceeded to transfer and print the PCB pattern directly onto the copper clad. For this process, we used laser printing because it is one of the most effective and commonly used methods in PCB fabrication. The toner from the laser printer acts as a protective layer on the copper surface during the etching process. We selected laser printing because it produces darker and more accurate toner lines compared to other printing methods. This helps ensure that the PCB traces remain complete and properly connected after etching. Accurate traces are very important in our stereo amplifier project because even small errors in the PCB lines can interrupt the flow of current and affect the performance of the circuit.

Note: The board may slightly bigger than the amplifier kit for extra space

After printing our PCB layout, our next step was to prepare the board for the etching process. We carefully dipped the PCB into a solution of Ferric Chloride, which is commonly used for etching printed circuit boards. During this process, the Ferric Chloride dissolved the exposed copper areas that were not protected by the printed PCB layout. As the unwanted copper was removed, the desired circuit pattern gradually appeared on the board based on our designed layout for the stereo amplifier circuit.

Once the etching process was completed, we removed the PCB from the solution and cleaned it thoroughly to remove any remaining chemicals and excess residue. After inspecting the board and confirming that the circuit traces were clear and complete, we proceeded to plot the drilling points according to the positions of the components in the amplifier kit. We carefully marked each location to ensure proper alignment of the electronic components during assembly. After plotting the guide points, we started drilling the PCB using the appropriate drill bit sizes. Drilling the PCB was an essential step because it created the holes needed for inserting the components such as resistors, capacitors, transistors, and connectors.

Note: Make sure to use the correct drill bits that would perfectly fit the components through my PCB. By doing this, We avoided problems such as loose components or holes that were too tight, which could make the parts difficult to attach and solder properly. Choosing the right drill size helped us ensure that every component fit securely and made the soldering process smoother and more reliable.

After we finished etching and drilling our PCB, we started preparing all the components needed for the amplifier project such as resistors, capacitors, diodes, transistors, and other electronic parts. Before placing them on the PCB. We carefully tested each component to make sure they were working properly and had the correct values. We used a multimeter to check the resistance, capacitance, and continuity of the components. Testing the components was very important because damaged or incorrect parts could affect the performance of the amplifier.

We also used a breadboard to test some of the components and the circuit connections before permanently installing them on the PCB. This helped us verify if the components were functioning correctly and allowed to replace any defective parts with extra components available.

Once we confirmed that all the components were working properly, We carefully inserted them into their proper positions on the PCB based on the circuit layout. After ensuring proper placement, we proceeded with soldering each component one by one, securing them firmly onto the board to complete the assembly process.

Note: When soldering components, make sure the lead was properly soldered through the components. Soldering lead was a conductive metal that once it attached it wrongly, it will create short circuit to your PCB. You can de-solder the components using solder pump to remove the lead for your PCB.

After soldering our amplifier, we proceeded to test the PCB to see if it would properly amplify sound to the speaker using 18 V AC as the power input. We connected the speaker to the PCB, along with the transformer, and used a smartphone as the audio input to check if the signal would be amplified correctly through the system.

Once the sound was successfully amplified through the speaker, we moved on to the next step, which was assembling the chassis box. However, if the circuit did not work as expected, we carefully inspected the PCB to identify any issues that needed to be fixed. In cases where damaged components were found, we replaced them using our spare components until the circuit functioned properly.

Once we tested the amplifier and confirmed that it was functioning properly, we proceeded with building the chassis box to house and protect the amplifier components. We determined the input and output connections for our speaker to ensure proper signal flow and performance. After identifying the appropriate terminals, we carefully mounted the components inside the chassis box and secured all wiring connections.

We then conducted another series of tests to verify that the amplifier and speaker were operating correctly. The results showed clear audio output and stable performance, indicating that the assembly and installation were successful. We successfully completed the construction of our 150 W Stereo Amplifier.

Overall, this project served as a significant stepping stone in our journey toward becoming professional electronics engineers. It challenged us not only to apply our technical knowledge, but also to strengthen our teamwork, dedication, and perseverance. Every stage of building the amplifier required patience, collaboration, and problem-solving, which made the entire experience both meaningful and rewarding.

Although designing and constructing an amplifier was challenging, it also became one of the most enjoyable parts of our learning experience. It pushed us to think creatively, innovate, and continuously improve our ideas in order to achieve the best possible outcome. Through this project, we discovered how engineering is not only about circuits and components, but also about passion, determination, and the ability to work together toward a common goal.

More than just completing a requirement, this project inspired us to grow as future engineers who are capable of creating, innovating, and turning concepts into reality. It reminded us that every challenge we overcome today brings us one step closer to becoming skilled and successful electronics engineers in the future.

“Victorious warriors win first and then go to war, while defeated warriors go to war first and then seek to win.”

-Sun Tzu