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Automatic Volume Control for Audio Amplifier

Category: Embedded Systems
Date: May 2025
Block diagram of audio amplifier with microcontroller

About this project

Designed and built a closed-loop audio amplifier system (THAT2180C VCA, LM380N PA, CA3140 VU Meter) on STM32 using MicroPython. Calibrated subsystem gains and offsets, characterized PA response from 100Hz to 50kHz, and implemented a control algorithm in Python with Jupyter+ipywidgets to maintain real-time loudness stability using RMS feedback. System reduces clipping and auto-adjusts volume.

Key Features

  • Analog + Digital Integration: Combined analog audio electronics with STM32 feedback loop using MicroPython.
  • Real-Time Volume Control: Maintains consistent RMS output using step-up/down logic and VU feedback.
  • PA Frequency Characterization: Measured and tuned amplifier response from 100Hz to 50kHz.
  • Clipping Protection: System detects saturation and reduces gain to prevent distortion.

Challenges

Tuning feedback loop timing, analog signal noise, and VU accuracy under dynamic load.

Learnings

Gained hands-on experience in embedded systems, control theory, audio electronics, and microcontroller firmware.