Signal Processing and Fast Verification Method for an Embedded Microprocessor Based PWM High-Fidelity Audio Playback System

A PWM high-fidelity audio playback system including only a general-purpose embedded microprocessor, switching power transistors and output filter has been designed and measured. The design uses digital signal processing and class D amplifier to amplify audio signals with high efficiency and low distortion. Signal processing uses sample rate conversion, noise shaping and equalization to convert high-fidelity PCM audio input to PWM output. A software approach that can verify the quality of the output before hardware implementation is discussed. Results measured on a prototype board show this approach delivers 200W into a 4 ohm loudspeaker with S3% efficiency, 96 dB SNR and 0.02% THD.