300 Watt Power Amplifier Circuit using Transistors

Hey music lovers! Want your speaker sound REALLY loud?

This 300 Watt Power Amplifier Circuit using Transistors show how to make very strong amplifier circuit.

It can give 300 watt sound with 8 ohm speaker or even more power with 4 ohm speaker.

WARNING: Be careful, this circuit uses high voltage and can be dangerous.

If possible try this project with adult watching.

For home use better ask trained electrician to install.

This project is not good for beginners so only try if anyone have some experience.

What is a 300 Watt Power Amplifier Circuit:

A 300 watt power amplifier circuit is electric circuit to make sound louder.

It gives around 300 watt output power.

This kind of circuit takes small audio signal and make it strong so it can drive speaker with loud and clear music.

Circuit Working:

Parts List:

To get high power and still keep good Hi-Fi sound this amplifier uses complementary transistors.

It use 45V + 45V power and with no more than 7A current.

Most transistors and some BC556 need to go on heatsink, usually on side of box to remove heat well.

Also we must use thermal grease to fix diodes A, B and C, 1N4007 to heatsink.

For best sound the music input should be 1Vpp line signal.

Formula:

When building a power amplifier with NPN and PNP transistors follow some easy formulas:

Bias:

Voltage divider bias is common method for NPN and PNP.

To find resistor R1 and R2 use formula:

R1 = (Vcc – Vbe) / Ib

R2 = (R1 × β) + Re (for NPN)

R2 = (R1 × β) – Re (for PNP)

where:

• Vcc is the power supply voltage
• Vbe is the base-emitter voltage which is around 0.7V for silicon
• Ib is the base current
• β (hFE) is the transistor gain
• Re is the emitter resistor which is optional for more stable)

Power Loss:

Check if transistor get hot too much for that use this formula:

Pd = (Vce × Ic) + (Vbe × Ib)

where:

• Vce is the collector to emitter voltage
• Ic is the collector current
• Vbe is the base to emitter voltage
• Ib is the base current

Transformer Turns Ratio:

In transformer-coupled design, turns ratio help match speaker to amplifier:

Np / Ns = √(RL / Rp)

where:

• Np is the primary coil turns which goes to amplifier
• Ns is the secondary coil turns which goes to speaker
• RL is the speaker resistance
• Rp is the wanted primary impedance based on transistor

Important:

For full amplifier design need more deep calculation as this is only some basic formulas.

Check circuit diagrams and data sheets for full help.

How to Build:

To build a 300 Watt Power Amplifier Circuit using Transistors following steps are required for connections:

Diagram Design:

• First get or make schematic diagram for 300 watt amplifier circuit.
• It show where to put transistors, resistors, capacitors and other parts.

PCB Design:

• Use the schematic to design PCB.
• Place parts on PCB with good space for heat and low noise.

Mounting Transistors:

• Put all transistors on PCB in right place.
• Use correct type as shown in circuit diagram.
• Be sure all connections are good.

Heatsink Connector:

• Fix heatsink on PCB in needed place.
• Put all transistors on heatsink except BC556 and diodes A, B, C and 1N4007.
• Use thermal grease to help heat go away better.

Positioning of Components:

• Place resistors, capacitors, inductors and diodes on PCB like in diagram.
• Check value and direction for polarity before solder.

Connecting:

• Connect wires to each part by following the PCB tracks.
• For high current use thick wires.

Power Supply Connection:

• Connect amplifier to power supply.
• Be sure voltage is 45V + 45V.
• Be careful to not make short circuit.

Testing:

• Before closing box test with 1Vpp audio input.
• Use multimeter or oscilloscope to check output signal.
• Fix any problem if needed.

The Enclosure:

• After testing is OK put circuit in box like enclosure.
• Be sure enough air can go inside to cool down parts.

Last Testing:

• Do final check of amplifier with sound.
• See if circuit work well and give expected performance.

Conclusion:

To build 300 Watt Power Amplifier Circuit using Transistors and to run big power amplifier we need some electronic knowledge.

High voltage and current can be dangerous so always follow safety.

References:

Design and Construction of A 300 Watt Audio Amplifier