/racoon

A bluetooth-based amplifier with advanced signal processing

GNU General Public License v3.0GPL-3.0

Racoon - Bluetooth Stereo Amplifier

A bluetooth-based amplifier iterating on the Opossum project, written primarily C/C++ for a specific hardware platform comprised of:

Table of Contents

General Info

This project is the 2nd gen evolution of a bluetooth stereo audio amplifier with a spetral-based automatic gain control. The 1st generation was concieved and started at a point before I had access to an online streaming service such as Spotify, who normalizes track levels across albums and artists. When playing back music without that normalization it often frustrated me when a quiet track would follow a loud track, or vice versa, and the playback volume would thus jump substantially in one direction or the other.

A bluetooth-connected amplifier utilizing a microcontroller continuously analyzing the audio spectrum and adjusting the playback amplifier volume accordingly, solves the issue!

Features

All 1st generation features maintained, plus the 2nd generation of this will platform will:

  • Streamline the platform from a hardware design perspective
    • unified BT+DSP system
    • digital audio volume control (no predefined gain steps)
    • custom PCBA minimizes size and increases reliability over 1st gen dev board solution
    • project is much more easily replicated
  • Add line-in/line-out functionality
  • Possibly add a display for displaying system and/or playback information
  • Expand EQ and DSP options beyond simple on/off functionality

Remaining Work

  • Bring up hardware hardware system
    • power control
    • GPIO
      • mute
        • line-in
        • line-out
        • amplifier
    • I2C/SPI
      • amplifier
    • bluetooth radio
      • establish BT connection
      • establish audio streaming
    • I2S audio system
      • ADC
      • DAC
      • Amplifier
    • display (not yet defined)
      • establish connectivity
      • display text
      • display images
  • route basic DSP (steel thread)
    • BT/line-in audio is routed to amplifier
    • BT/line-in audio is routed to DAC
    • ADC audio is selected over BT audio if
      • Line input is active
      • BT connection/A2DP is either not established or audio is not streaming
  • port User Experience from Opossum to use as a starting point
    • port DSP processing (automatic gain control)
    • port User Interface
      • Buttons
      • Volume Control
      • LED Control

Status: This project is in the pre-development stage.

(C) 2021-2021, Winry R. Litwa-Vulcu