ESP32 Bluetooth Audio Receiver with Amplifier and Tone Control for Speakers

Many older wired speakers still sound fine, yet modern phones have dropped the 3.5 mm headphone jack, leaving a working speaker pair with no convenient way to play phone audio through it. Buying a new Bluetooth speaker replaces hardware that still works, while cheap plug-in Bluetooth dongles hide their audio path, amplifier limits and tone controls inside a sealed case, so a student learns nothing from them. The ESP32 Bluetooth Audio Receiver with Amplifier and Tone Control for Speakers closes that gap by turning an ordinary wired speaker pair into a Bluetooth speaker through an open, inspectable build: an ESP32 board receives the phone audio stream, a dedicated DAC converts it to analogue sound, a three-knob tone stage shapes bass and treble, and a Class-D amplifier drives the speakers. Every stage is visible, measurable and explainable, which is exactly what an electronics project should demonstrate.

The signal chain runs end to end from the phone to the speakers in six stages. The phone sends music over Bluetooth Classic using the A2DP profile, with the SBC codec carrying the compressed audio. The ESP32, acting as an A2DP sink, receives that stream, decodes the SBC frames back into digital audio samples, and re-clocks those samples out over its I2S bus. The PCM5102A DAC converts the I2S samples into a stereo analogue signal, which then passes through the tone-control stage where the bass and treble knobs boost or cut their frequency bands. Finally, the PAM8403 Class-D amplifier raises the shaped signal to speaker level and drives the wired speaker pair, so the sound heard from the speakers is the phone's audio, processed through a fully visible hardware chain.

1. The receiver is powered from a 5 V DC adapter and the pairing button puts the ESP32 into discoverable mode, shown by a blinking status LED.
2. The phone finds the receiver in its Bluetooth audio device list, pairs once, and stores the pairing for automatic reconnection later.
3. Playing music on the phone sends the audio over Bluetooth Classic using the A2DP profile, with SBC as the mandatory audio codec.
4. The ESP32 firmware receives the A2DP stream, decodes the SBC frames into digital audio samples, and outputs them over the I2S bus.
5. The PCM5102A DAC converts the I2S samples into a stereo analogue signal for the tone-control stage.
6. The NE5532 tone stage applies the volume, bass and treble knob settings to the analogue signal before it reaches the amplifier.
7. The PAM8403 Class-D amplifier raises the shaped signal to speaker level and drives the wired speaker pair, with play, pause and track-skip commands handled over AVRCP.

Tech stack:

• ESP32-WROOM-32
• Bluetooth Classic · A2DP sink
• PCM5102A I2S DAC
• PAM8403 Class-D amplifier
• NE5532 tone-control stage
• ESP-IDF Bluetooth stack
• Arduino IDE firmware
• I2S digital audio

The ESP32 Bluetooth Audio Receiver with Amplifier and Tone Control for Speakers combines four capabilities that make it a complete audio-system project rather than a single-board demo. First, the ESP32 acts as a Bluetooth A2DP sink, so any phone can stream music to it without an app or an internet connection. Second, the digital audio leaves the ESP32 over I2S into a dedicated PCM5102A DAC, keeping conversion quality out of the microcontroller's noisy internal converters. Third, an analogue tone-control stage with separate volume, bass and treble knobs lets the listener shape the sound by hand. Fourth, a PAM8403 Class-D amplifier stage delivers real speaker-driving power, with a datasheet value of 3 W per channel into a 4 Ω load at a 5 V supply. The tone stage and amplifier are deliberately separate modules, so a reviewer can trace the signal from the phone through conversion, shaping and amplification without any hidden processing in between.

• [Bluetooth A2DP sink reception] The ESP32 advertises as a Bluetooth audio receiver, pairs with a phone, and accepts the standard A2DP audio stream with SBC codec decoding handled on the board.
• [I2S DAC audio path] Decoded audio leaves the ESP32 over I2S into a PCM5102A DAC, so the analogue signal comes from a dedicated converter instead of the microcontroller's internal DAC.
• [Analogue bass and treble tone control] A NE5532-based tone stage provides separate volume, bass and treble knobs, with a design target of approximately ±12 dB of bass adjustment at 100 Hz and treble adjustment at 10 kHz.
• [Class-D stereo amplifier] A PAM8403 amplifier module drives a stereo speaker pair, with a datasheet value of 3 W per channel into a 4 Ω load at a 5 V supply and 10% total harmonic distortion.
• [Phone-side playback control] AVRCP support lets play, pause and track-skip commands from the phone control the stream, so the phone remains the remote control for the system.
• [Automatic reconnection] The receiver stores its last pairing and reconnects to that phone automatically when both are powered and in range, without repeating the pairing step.
• [Pairing status indication] A push button starts pairing mode and an onboard LED shows pairing, connected and streaming states, giving a visible check at every stage of the link.

• Assembled ESP32 Bluetooth audio receiver with amplifier and tone-control stage
• Firmware source code for A2DP sink, I2S output and AVRCP control
• Circuit diagram and wiring documentation for the ESP32, DAC, tone stage and amplifier
• Component list with module part numbers and supply ratings
• Setup and pairing instructions for phone connection and reconnection
• Project report PDF (background, audio chain theory, methodology, results)
• PPT presentation for final review
• Viva Q&A preparation document (Bluetooth profiles, SBC codec, I2S, DAC operation, Class-D amplification, tone-control theory)