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Maxim > Design Support > Technical Documents > Reference Designs > Amplifier and Comparator Circuits > APP 5147
Maxim > Design Support > Technical Documents > Reference Designs > Power-Supply Circuits > APP 5147
Keywords: audio, Bluetooth, wireless, stereo
REFERENCE DESIGN 5147 INCLUDES: Tested Circuit Schematic BOM Description
Simple Wireless Bluetooth Stereo Audio System for
Outdoor Use
By: Marko Kannisto
Jun 11, 2012
Abstract: When people want portable music, they usually rely on battery-powered audio devices. With a bit of
engineering blood (or curiosity) running in your veins, it is not difficult to build a wireless Bluetooth® stereo audio
system that can be controlled with any device that has a Bluetooth connection and a music player.
A similar version of this article appeared in the May 10, 2012 issue of Electronic Design magazine.
Pretend that the weather is warm and it is a nice time to be outdoors chatting with friends. You want some
background music, but where will it come from?
When people want portable music, they usually rely on battery-powered audio devices. Of course you can buy a
sound system for outdoor use, but those can be quite expensive and, as we shall show, unnecessary. With just a
bit of engineering blood (or curiosity) running in your veins, it is not that difficult to build a wireless Bluetooth®
stereo audio system that can be controlled with any device that has a Bluetooth connection and a music player.
This application note describes how to build a simple and fairly low-cost wireless Bluetooth stereo audio system
for outdoor use. The system has 20W
RMS
output power. It can be controlled either with a handset that has a
Bluetooth connection and a music player, or with an Apple® iPod® model. Three appendices discuss additional
layout considerations, the differences between using a Class D and Class AB amplifier in the design, and the cost
of the system.
Bluetooth Basics
Bluetooth technology was created on 1994 and is widely used to establish a short-range wireless connection
between two handheld mobile devices. A Bluetooth setup also lets you transfer a stereo audio signal from a
handheld device to a wireless headset. Today's Bluetooth headsets operate under the Bluetooth Class 2
specification with 2.5mW (4dBm) transmission power. The transmission range for a Bluetooth Class 2 module is
approximately 10 meters.
Putting the Bluetooth Audio System Together
Bluetooth headsets are usually used with fairly small-sized, 32Ω speakers. By connecting the audio signal from a
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