ATmega328P-PU + VS1053 Based MP3 Player

The MPEG-1 or MPEG-2 Audio Layer III (MP3) is an audio coding format used to shrink the size of a large audio file into a smaller one (about 8.33% of the original file size), without affecting its sound quality. It is the most popular audio format downloaded and played on most digital audio players. Digital audio players basically use a digital signal processor (DSP) and a digital-to-analog converter (DAC) to play an MP3 file. The DSP processes the MP3 data and sends it to the DAC to convert it into an analog signal that can be heard if inserted into an audio amplifier with a loudspeaker. Read more

30W Stereo Audio Amplifier with Clipping Protection

This reference design features a 30W stereo audio amplifier that employs a motorized slide potentiometer to provide clipping protection. The PSM60-081A-103B2 is a half-watt, 10kΩ, 60mm, motorized slide potentiometer. It provides two built-in 10kΩ variable resistors labeled as line track and servo track. The line track variable resistor can be used for other purpose, while the servo track variable resistor can be used for tracking the position of the potentiometer lever. The built-in DC motor controls or adjusts the position of the potentiometer lever as well as the resistance of the line track and the servo track variable resistors. Read more

40W Class-D Audio Amplifier with Digital Master Volume Control

The OPA1688 device used in this design belongs to the SoundPlus family of Texas Instruments. It is a low-noise operational amplifier designed for audio applications. It can either operate using a single voltage supply or a split voltage supply. The MAX5486, which is also used in this project, is a dual 40kΩ digital logarithmic potentiometer that has a debounced pushbutton interface ideal to control the volume and balance the left and right channel of this project. It has 32 log-spaced tap points with a buffered wiper. The power amplifier in this design is the TPA3106D1, which is a 40W class-D audio power amplifier with 92% efficiency that eliminates the need for an external heat sink. Read more