In the realm of DIY electronics, audio processing is an exciting area to explore, especially if you're an audio enthusiast looking to build a custom sound system for your home or workspace. Audio processors, which are responsible for processing and enhancing the sound signal, can be both fun and rewarding to design. Today, we will dive into creating a Digital Audio Processor (DAP) using the SM5847 audio DSP (Digital Signal Processor) IC.
The SM5847 is a powerful, high-performance chip designed for handling a range of audio processing tasks, including digital-to-analog and analog-to-digital conversions, equalization, volume control, and mixing. This project will use the SM5847 as the central component to build a home audio processor that enhances the quality of your music playback and allows you to experiment with various audio effects.
Project Overview
The goal of this project is to create a digital audio processor for a home audio system, incorporating the SM5847 for its processing power. The processor will receive digital audio signals from a source device (e.g., a smartphone, MP3 player, or computer), apply processing effects such as equalization, volume control, and dynamic range compression, and output the enhanced audio to speakers or an amplifier.
The SM5847 chip is capable of handling multiple audio processing functions and provides high-quality conversion between digital and analog audio signals. By combining it with some additional components, such as a microcontroller for control, a display for user interface, and a power supply, we can build a robust audio processor.
Components Needed
● SM5847 Audio DSP IC – This is the core of the audio processor, handling the digital signal processing tasks.
● Microcontroller (e.g., ATMEGA328P) – To control the SM5847 and handle user inputs.
● LCD Display – For showing settings such as volume, equalizer levels, or mode selections.
● **Digital-to-Analog Converter (DAC) – For converting the processed digital audio back to analog for output to speakers.
● Power Supply (5V/12V DC) – To power the components of the circuit.
● Potentiometer – For manual volume control.
● Audio Jacks – To connect the input (e.g., from a smartphone) and output (e.g., to an amplifier).
● Capacitors and Resistors – For signal conditioning and filtering.
● Buttons or Rotary Encoder – To allow the user to interact with the system for adjusting settings.
● PCB or Breadboard – For assembling the circuit.
● Amplifier – Optional, for driving speakers at higher volumes.
Step 1: Understanding the SM5847 and Its Capabilities
The SM5847 is a highly integrated audio processor IC that supports a variety of audio processing tasks. It is designed to handle multiple types of digital audio signals, including those from PCM (Pulse Code Modulation) sources. Its primary functions include:
Digital-to-Analog Conversion (DAC): Converts digital audio signals into analog signals that can be sent to speakers or amplifiers.
Analog-to-Digital Conversion (ADC): Allows you to digitize analog audio signals, such as those from microphones or other analog audio sources.
Signal Processing: Includes a range of effects like volume control, tone adjustment, equalization, and dynamic range compression, all of which can enhance the audio experience.
Stereo Mixing and Routing: The SM5847 supports mixing and routing of stereo signals, which is useful when dealing with multiple audio sources.
The SM5847 is versatile and can be controlled through an external microcontroller, which can adjust parameters like volume, equalizer settings, and effects in real-time. Its ability to process both digital and analog signals makes it an excellent choice for audio applications.
Step 2: Circuit Design
The next step is to design the circuit around the SM5847 and connect it with the necessary components for audio input, processing, and output.
2.1 Powering the Circuit
The SM5847 operates on a 5V power supply. To ensure stable operation, use a regulated 5V DC power source. You will also need a separate power supply for the audio amplifier if you're driving speakers directly. Use capacitors (e.g., 100nF and 10µF) near the power pins to filter out noise and provide clean power to the SM5847.
2.2 Input Stage: Connecting the Audio Source
To input the audio signal, use a standard 3.5mm stereo jack for connecting devices like smartphones, MP3 players, or computers. The audio signal will typically be in the form of an analog signal, so it needs to be converted to digital format for processing by the SM5847. This can be done with an Analog-to-Digital Converter (ADC), which may already be included in the SM5847 depending on your configuration.
If you're working with a purely digital audio source (e.g., a digital audio player or a computer), you can connect the digital audio directly to the SM5847 via a SPDIF input or I2S interface. Ensure that the input signal's sample rate and format match the SM5847’s capabilities.
2.3 Audio Processing: The SM5847 at Work
Once the audio signal is received, the SM5847 will process the signal according to the parameters you set. These parameters could include:
● Volume Control: Adjusting the amplitude of the signal.
● Equalizer Settings: Boosting or cutting specific frequency bands (bass, mid, treble).
● Dynamic Range Compression: Reducing the difference between the loudest and quietest parts of the audio.
● Other Effects: Adding effects such as reverb, delay, or balance adjustments.
The microcontroller (such as an ATMEGA328P) will control the settings of the SM5847. The microcontroller communicates with the SM5847 via an I2C or SPI interface to adjust the audio processing settings in real-time based on user input. A potentiometer can be used for volume control, while buttons or a rotary encoder can be used to adjust the equalizer settings or toggle between different audio effects.
2.4 Output Stage: Converting Digital to Analog
After processing, the digital audio signal needs to be converted back to analog before it can be sent to an amplifier or speakers. The SM5847 has an internal Digital-to-Analog Converter (DAC), which converts the processed signal to analog output. If additional output control is needed, you can use external DACs to further enhance audio quality.
For the output connection, you can use 3.5mm stereo jacks or RCA connectors, depending on your audio system's requirements. The processed analog signal will be sent to an external amplifier or speaker system for playback.
2.5 User Interface: Controls and Display
To interact with the audio processor, you'll need a user interface. An LCD display (16x2 or similar) can be used to show information such as the current volume, equalizer settings, or active effects. This display can be controlled by the microcontroller, which will update the display based on user interactions.
For user input, you can use a potentiometer for analog volume control, as well as buttons or a rotary encoder to adjust other settings like the equalizer bands or toggle different audio effects. These inputs are read by the microcontroller, which then communicates with the SM5847 to update the settings accordingly.
Step 3: Building the Circuit
With the design in mind, we can now proceed to the physical assembly of the circuit.
Assemble the power supply. Start by setting up the 5V DC regulated power supply to power the SM5847 and microcontroller.
Connect the audio input. Use a 3.5mm jack or digital interface for the audio input, depending on your audio source.
Connect the SM5847. Wire the power, ground, and audio input to the SM5847 according to its datasheet. Connect the audio output pins to the DAC or analog output section.
Connect the microcontroller. Wire the microcontroller to the SM5847’s control interface (I2C or SPI) and connect the user interface components (LCD, potentiometer, buttons).
Test the connections. Before powering the circuit, double-check all connections to ensure proper wiring and grounding.
Step 4: Programming the Microcontroller
Once the hardware is assembled, the microcontroller needs to be programmed to handle user input and control the SM5847’s audio processing settings. The program should allow the user to adjust the volume, equalizer settings, and toggle between different audio effects. The microcontroller will send commands to the SM5847 via I2C or SPI to adjust these settings.
Step 5: Testing and Calibration
After assembling the circuit and uploading the program, it’s time to test the audio processor. Plug in an audio source, such as a smartphone, and check if the audio is processed and output through the speakers. Adjust the volume, equalizer, and effects using the user interface and ensure that the changes are reflected in the audio output.
You may need to fine-tune the settings and make adjustments to the program or circuit based on your testing.
Conclusion
Building a digital audio processor using the SM5847 is an exciting and rewarding DIY project that can significantly improve the audio quality of your home sound system. With the SM5847’s powerful audio processing capabilities, you can easily create a custom processor that handles volume control, equalization, dynamic range compression, and other audio effects.
This project not only provides a hands-on learning experience in audio electronics but also allows you to create a versatile and high-quality audio processor that can be tailored to suit your specific needs. Whether you're building a personal audio system or experimenting with audio effects, the SM5847 offers an excellent platform for exploring the world of digital audio processing.