Bluetooth Speaker

This project is a complete DIY Bluetooth speaker system built around a custom-designed 15W Dual-Channel Audio Amplifier. The core of the project is the amplifier PCB, which was routed and designed from scratch using KiCad 9.0. Rather than just designing a bare board, I integrated this custom amplifier with a local VT09 MP3/Bluetooth decoder module and a dedicated power supply. The result is a fully functional, high-fidelity wireless audio system that demonstrates how custom PCB design can be seamlessly integrated into a finished consumer-style product.

 The focus is always on practical, implementable engineering. It is easy to design a circuit on a screen, but the real challenge and fun comes from building something you can use every day. I wanted to participate in the KiCad Design Contest by building something tangible. I decided to make this because it allowed me to tackle several hardware challenges at once: clean audio routing, thermal management for a 15W load, and system-level integration. Taking a bare KiCad layout and pushing it all the way to a finished, great-sounding speaker bridges the gap between raw hardware design and a practical, everyday application.

The system operates through three main stages: Power, Signal Processing, and Amplification.

The Source (VT09 Module): The VT09 handles the wireless Bluetooth 5.0 connection, USB playback, and FM radio. It acts as the brain of the user interface, decoding the digital audio and outputting a clean, line-level analog stereo signal.

The Amplification (Custom KiCad PCB): The line-level signal from the VT09 is fed directly into the custom KiCad amplifier board. The board utilizes an efficient amplifier topology to boost the signal. To ensure a low noise floor (preventing that annoying Bluetooth "buzz"), the PCB layout utilizes strict star-grounding techniques to isolate the audio signal ground from the power ground. Localized decoupling capacitors filter the power delivery, and the trace widths are optimized to handle the current required for 15W per channel continuous output.

The Output: Finally, the amplified signal drives two full-range speakers, powered by a robust 12V supply that ensures the system has enough headroom to handle deep bass hits without voltage sag or clipping.

Component Used:

1 x 15W Class D Audio Amplifier

1 x 15W 3A Power supply PCBA

1 X Bluetooth MP3 Decoder Module BT-V09 M

1 x 5V 2A Power Adapter with Micro USB cable

2 x 10W Speaker Driver

Connection:

From Bluetooth Decoder module to Amplifier board

Connect RO to RIN +, LO to LIN

AG to RIN- & LIN-

Powering up the audio amplifier with the 15V 3A power supply pcba

Powering up Bluetooth Decoder Module with 5V 2A power Adapter with microUSB

Finally Connect Speaker driver with Amplifier board Rout and Lout.

Lets see a short the Testing video with 50% volume:

Lets check some assembly snaps: