How to Build a High-Power Stereo Audio Amplifier Using the LS4440

LA4440 is a very popular dual channel audio amplifier which is often used to build high power audio amplifiers. This IC is known for its high power, ease of use and cheap price which makes it popular in home theater and car amplifier systems that work with 12V. So, in this article, we will learn how to build a high power stereo audio amplifier using LS4440 audio amplifier IC. The circuit will have two LS4440 amplifier ICs and will be able to drive two 20W speakers (20W+20W) with volume, bass and treble control. Moreover, the audio input to our amplifier board can be provided directly from the audio jack or wirelessly using Bluetooth.

LA4440 Integrated Circuit

Before we start building this amplifier, let us learn more about LA4440 power amplifier IC to understand its technical specifications so that we can design our amplifier effectively. As shown below, LA4440 is a 14-pin linear audio amplifier IC developed by Sanyo.

This IC can be used as a mono audio amplifier or a stereo two-channel audio amplifier. It has dual enabled modes, namely, stereo mode and bridge mode. The main difference between these two configuration modes is that in stereo mode, a single IC can drive two speakers with a maximum of 6W + 6W, which means only a 12-watt load, but in bridge mode configuration, you will get 19W of audio output from a single IC for a single speaker. Therefore, we need 2 ICs to make stereo and 2 copies of the same circuit, which we will discuss in the circuit diagram section. Here, I have configured the audio amplifier in bridge mode to get a 20 W + 20 W powerful audio output. Since our design has two ICs, it is also called a 4440 dual IC amplifier circuit. Apart from this, our audio amplifier IC has the following advantages.

It has good ripple suppression 46db

Good channel separation

Low residual noise

Bass Audio restores a wide range of music from low to high frequencies.

Small popping or startup noise

Built-in audio mute function

Built-in protection: overvoltage protection, surge voltage protection, pin-to-pin short circuit protection.

Minimal spare parts required

What is ripple rejection and why is it important?

Ripple is the variation of voltage and current from a steady state value which can vary with load, which creates noise at the output of the circuit resulting in distortion. To overcome this, filters are used which help suppress this noise/ripple. This is called ripple rejection. The LA4440 IC provides a good ripple rejection value of 46dB.

What is channel separation?

When a single IC package contains multiple op amps (LA4440 IC has 2 channels), one op amp can affect the performance of another op amp. To prevent this problem, the LA4440 IC provides good channel separation. The internal block diagram and pinout are shown below.

40W Dual IC Stereo Audio Amplifier Required Materials

Listed below is a complete stereo audio amplifier materials list. Most of the components used should be easily available as they are commonly used in audio amplifier circuits.

LA4440 dual IC amplifier circuit

The complete 4440IC amplifier circuit diagram is shown in the image below. Due to the high power nature of the circuit, it is not recommended to use a breadboard to build this circuit. Therefore, we will build the PCB at home by designing an audio amplifier PCB for this circuit.

I have connected capacitors C13 and C14 on the first IC and C23 and C16 on the second IC to IC pins 1 and 7. These capacitors are called feedback capacitors. The low cutoff frequency of our amplifier depends on the value of these capacitors, if the value increases, the start-up time will be delayed. The voltage gain of these capacitors on IC 1 and 2 can be adjusted by changing the value of resistors R1 and R2 respectively.

Capacitors C15 and C19 of the first IC and C20 and C21 of the second IC are connected to the output of IC pins 9 to 10 and 13 to 12. These capacitors are called bootstrap capacitors and are used for bass or low frequency adjustment.

C3 and C4 are very important capacitors. The value of this capacitor should be high, usually 2200uF 35V or 4700uF 35v is recommended for mains filtering and load handling. The capacitors are rated for 1Amp to 3Amp to improve the sound quality. Capacitors C2 and C5 are filter capacitors used to filter the audio input given to our amplifier IC.

Capacitors C18 and C17 are bypass capacitors used for noise filtering in audio systems or other electronic circuits. When an active device like our audio amplifier is connected to a power supply, the current consumed by our device creates a voltage drop across the power supply. Due to the varying impedance of our loads and multiple active loads connected on the same path, the current draw fluctuates and creates more voltage spikes and ground bounce. To avoid this problem, we typically use bypass capacitors in the loads to provide a bypass path for the transient current instead of flowing through the common path.

LA4440 Audio Amplifier PCB Design

As mentioned earlier, this circuit involves high current paths, so it cannot be built and tested on a breadboard. Therefore, we designed a PCB for the above circuit using Eagle software. You can use any PCB design software of your choice. Also, if you don’t want to design a PCB, you can solder the circuit directly on a perfboard. My PCB layout is shown in the image below.

We will use this PCB design layout to build our own PCB at home.

The PCB is designed with two audio inputs, one is through aux and 3.5mm audio jack via direct audio cable, and the other is for wireless Bluetooth connection. We also use screw terminals to power the board and connect two 20W speakers. Potentiometers are used to control volume, bass and treble.

Building PCBs using the toner transfer method

To demonstrate this project, we created our own PCB using the Toner transfer method. The following image shows the various stages in the manufacturing process of our board.

Check out the image given below to see how the homemade PCB looks like after drilling all the component pads. As you can see, the board becomes neat and the pads are all clear and distinct.

Once the board is read, you can insert and solder all the components to the custom PCB. The components I used to solder the board are shown below. Here, I have used a dual channel potentiometer to control the volume, bass, treble. For the power supply, you can use a 12v 1 Amp to 3 Amp power supply or a 12V battery.

The two pin screw terminal is used to provide power and connect the speaker. The three pin screw terminal is used to provide audio input. We have also added a mini onboard Bluetooth module because nowadays people love to play songs directly from their phones, obviously through wireless connection. You will also need to insert a male and female header so that you can remove and change it easily. For the power supply of this Bluetooth module, I have used a LM7805 positive voltage regulator IC, which helps to control and drop the voltage from 12 V to 5 V.

Please note that I had to remove the diode bridge portion from the PCB to reduce the size and make it compact circuit size. But for the transformer power supply, you need to make a diode bridge with four 5408 general purpose 3 amp diodes before giving input to this amplifier circuit. The image given below shows how it looks like after all the components are soldered.

LA440 Amplifier Circuit Operation

Once the board is ready, we can test it by connecting the speaker directly and powering it. Audio input can come from a 3.5mm audio jack (three pin screw terminal) or through our Bluetooth module.

Audio Amplifier Design Tips and Considerations

The LA4440 or CD4440 IC has a built-in thermal shutdown feature and it dissipates a lot of heat. So, install a good heat sink to extend the lifespan. Also, you can install a cooling fan on the amplifier cabinet. It is a common problem that the amplifier may be affected by noise and create a humming sound. To avoid audio amplifier noise problems, make sure to check the following.

The heat sink shares the GND with the negative terminal of the power supply.

Use several large capacitors like 2200uF, 4700uF or 6800uF or 10000uF 25v or 50V capacitors in the mains filter and rectification stages for best results. Do not use a transformer power supply as it is not needed for battery operation.

The volume, bass and treble potentiometer bodies should be grounded together with the negative pole of the power supply.

Use metal enclosure/cabinet

Also, the noise depends on good grounding of the mains, which should be connected to the cabinet.

You can also use audio transformers for isolation and noise filtering.