Project Hub /Audio Displays & Interactive Media/Analog Audio & Amplifier Circuits/A Simple Audio Amplifier With Dual Power Source

Beginner

ANALOG / DISCRETE

₹500 – ₹1,500

3 – 6 Hours

Partial Kit

A Simple Audio Amplifier With Dual Power Source

A simple 19W audio amplifier built using the LA4440 IC and LM7812 regulator, supporting a dual power source of AC mains or a 12V car battery.

Originally published on ElectronicsForU

View original tutorial

Parts You'll Need

This project is sourced from another site, not written by us — this list is our best match of their components against what we stock, not a verified bill of materials. Always check the original blog (linked above) for the actual parts list before buying.

10pcs 5mm RED Diffused Light Emitting Diodes - LEDs Set Rs. 39.00
10pcs - 220 ohm 1/4 W Resistor Set Rs. 39.00
2-Slot 18650 Holder with Protective Cover and On/Off Switch – Case Rs. 109.00
DC Motor Plastic Fan Blade Rs. 19.00
400 Points Mini Solderless Prototype PCB Breadboard High Quality Rs. 89.00
MB102 Adjustable Breadboard Power Supply Module (3.3V & 5V) for Arduino & Raspberry Pi Rs. 139.00
Jumper Wire 10 Pin Male To Male 20cm Rs. 45.00
Jumper Wire 10 Pin Male To Female 20cm Rs. 45.00

Selected: Rs. 0.00

This list includes a generic resistor set as a placeholder — it is not matched to the exact value or part number this circuit needs. The correct one is specified on the original source page linked above; check it before buying.

We don't carry yet: Voltage Regulator IC (7805 / LM317 / 1117)
Speaker / Audio Amplifier
Diodes (1N4007 / 1N4148 / Schottky / Zener)
Capacitors
Header Pins / Terminals / Connectors
Transformer

Browse all components

How It Works

This audio amplifier project features a dual power source configuration capable of operating from either 230V AC mains or a 12V DC source, making it versatile for both fixed and mobile environments. When powered by AC mains, the 230V AC primary to 15V 1A secondary transformer steps down the high voltage, which is then converted into pulsating DC by the 1A bridge rectifier (BR1). Filtering and smoothing are handled by bulk electrolytic capacitors, including the 1000μF 35V capacitor, to supply stable DC to the rest of the circuit. For regulated voltage needs, the LM7812 12V voltage regulator (IC1) ensures a steady 12V output. An SPDT switch (S1) allows users to select between the power sources, with a 5mm LED (LED1) and a 680-ohm current-limiting resistor serving as a power indicator. The audio signal enters the system through a mono jack (CON2) and passes through coupling and feedback capacitors (such as the 47μF 35V and 100μF 35V units) along with a 1-kilo-ohm and a 100-kilo-ohm resistor network to properly bias the input signal for the LA4440 audio amplifier IC (IC2). The LA4440 amplifies the audio waveform to drive an 8-ohm 20W speaker (LS1) connected via a 2-pin connector (CON1). Because both the LA4440 amplifier and the LM7812 regulator dissipate thermal energy during operation, dedicated heatsinks are attached to keep their temperatures within safe operating limits.

Why Build This

Design and analyze a practical analog audio amplification stage coupled with a linear voltage regulation power supply suitable for undergraduate electronics coursework.

Investigate dual-source power switching topologies that transition between stepped-down AC mains power and a 12V DC automotive supply.

Apply thermal management principles by properly sizing and installing heatsinks for both the linear regulator and the audio power amplifier ICs.

Real-World Application

Portable or home audio amplification systems, car audio setups, and general DIY electronics hobbyist speaker systems.

Skills You'll Learn

Linear power supply design

AC-to-DC rectification and filtering

audio signal biasing and coupling

thermal management with heatsinks

analog amplifier integration

Safety Precautions

Exercise caution when working with 230V AC mains power during transformer and power supply wiring.

Technology Tags

AUDIO AMPLIFIER

LA4440

LM7812

POWER SUPPLY

PCB DESIGN

BREADBOARD

TRANSFORMER

BRIDGE RECTIFIER

Frequently Asked Questions

Why does the circuit use both a transformer and a voltage regulator?

The transformer steps down high AC voltage from the wall, and the bridge rectifier creates a rough DC supply. The LM7812 regulator then cleans and stabilizes this voltage to a fixed 12V to protect sensitive parts of the circuit.

Can I connect this amplifier directly to a standard 230V wall outlet without the transformer?

No, absolutely not. Connecting the circuit directly to 230V AC without the specified transformer will instantly destroy the components, ruin the board, and create a severe electrocution hazard.

What is the purpose of the heatsinks included in the parts list?

The LA4440 amplifier IC and the LM7812 regulator dissipate significant heat during normal operation, especially when driving a speaker or dropping high voltages. Heatsinks are required to prevent these components from overheating and triggering thermal shutdown or permanent failure.

Gallery

This page is part of Kitkraft's Project Hub — a curated collection of electronics & robotics projects gathered from the maker community to help students and hobbyists discover and learn to build. Kitkraft does not claim authorship of the original project, and makes no representation as to the accuracy, completeness or safety of third-party source material. The summary and "How It Works" explanation above are AI-generated, rewritten with reference to the original tutorial — not a reproduction of it. Full credit and a direct link to the original source are provided above. If you're the original creator and have a concern about how your work is represented here, please contact us and we'll address it promptly.

Kitkraft Project Hub — curated from the maker community, credited at the source.

PRJ-00774