bluetooth amplifier kit
Version 1.2
Bluetooth Amplifier
Index of Sheets
Index of Sheets
Main Features
Power Specification
PCB Connections
Build Instructions
Checking Your Bluetooth Amplifier PCB
Operating Instructions
Designing the Enclosure
How the Bluetooth Amplifier Works
Online Information
Main Features
3W audio amplifier with Bluetooth link (based
on a fully CE compliant module).
Operates from a 1A USB supply or LiPo battery
(both available separately).
Supports both 4Ω and 8Ω speakers.
Play music from a phone, tablet or computer
Includes automatic LiPo battery charging for
battery capacities between 400mAh and
Simple user interface, via single on / off switch.
Automatic power switch over between PSU and
battery (when battery present).
Auto reconnects to last device on power up
unless it can’t be found when it enters pairing
28 hours continuous operation off a 1000mAh
battery at ‘normal’ volume.
LED and sounds indicate status information
such as ‘paring’.
Slide switch supplied unmounted so an
alternative power switch can be used.
Optional connection point for off board LED,
for designs where the USB power and LED want
to be on different enclosure faces.
Speakers supplied unconnected allowing cable
lengths and cable routing to be personalised to
specific enclosure designs.
Pauses music when the phone rings and diverts
audio back to the handset (subject to
compatible phone).
Bluetooth Amplifier
Power Specification
Operating Voltage (USB supply)
4.5V – 5.5V
Supported LiPo Battery Capacity
400mAh to 1000mAh
Operating voltage (LiPo battery)
3.1V – 4.2V
Nominal Current in standby mode
5 mA
Nominal Current ‘normal’ volume
35 mA
Nominal Current max volume
120 mA
Note: USB power supply. It is important to use a high quality USB power supply that can deliver a minimum of 1A
while also providing a stable 5V supply. If this is not the case ‘clipping’ or ‘cutting out’ may be experienced when
used at high volumes.
PCB Connections
Bluetooth Amplifier
Build Instructions
Before you start, take a look at the Printed Circuit Board (PCB). The components go in the side that all of the
components are located on and are soldered from the bottom (blank) side of the PCB.
One of the two following power switch options must be used.
On-board (this is the normal option)
Solder the PCB Mount Right Angled On / Off Switch into the PCB where it is marked
‘SW1’. The row of three pins that exit the back of the switch must be soldered but the
other two pins don’t need soldering. Make sure the switch is all the way in and flat to
the PCB before soldering.
Off-board (if the switch needs locating away from the PCB)
It is possible to replace the supplied PCB mount power switch with one that is mounted
off the PCB. If this is done the two terminals of the desired power switch should be wired
back to the PCB and soldered to the two terminals shown right. It does not matter which
way around the wires are connected.
The cable and switch used should both be rated for a minimum of 1A @ 5V. This cable
should be kept as short as is possible and no longer than 150mm.
The kit is supplied with a metre of twin cable. This cable will be used to connect the two
speakers. You will need to cut this to the required length to connect each speaker in your
enclosure design.
Take each piece of twin cable and strip & tin the ends of the wire. Connect one end of
each wire to the two terminals on each speaker (as shown). If you have chosen one of
the product options that includes speakers you will see that the speakers have ‘+’ and ‘-’
indicators. Take the cable connected to one speaker and feed it through the strain relief
hole and connect it to the pads labeled ‘Speaker R’ on the PCB. The connections on the
pads are also labeled with a ‘+’ and ‘-’. The ‘+’ on the PCB needs to go to the ‘+’ on the speaker and ‘-’ to ‘-’.
Repeat with the second speaker, this time connecting to the pads labelled ‘Speaker L’.
If you are using your own choice of speakers then make sure both speakers are connected the ‘+’ and ‘-’ in the same
Bluetooth Amplifier
It is possible to add a second LED (like the example shown to the right) that is
mounted off the PCB. This mimics the LED on the PCB and can be used in designs that
require the LED to be positioned in a different place.
Important note: No current limit resistor is needed.
If this is done the two legs of the desired LED should be wired back to the PCB and soldered to the two terminals
labelled ‘LED2’. The long LED leg (Anode) should be soldered to the ‘+’ terminal and the short LED leg (Cathode)
should be soldered to the ‘-’ terminal.
The circuit has a built in LiPo battery charging circuit that allows it to be used in
rechargeable, portable designs. Battery capacities of between 400mAh and
1000mAh are supported. When a suitable battery is connected it will power the
PCB and the battery will be charged if it is also plugged into a micro USB power
It is important that the polarity of the battery is correct. The JST connector on
the PCB labelled ‘CON2’ and the pin next the bottom right mounting hole is the
positive battery connection (as shown in the picture right). This should be
checked before connecting a battery.
The power switch will need to be in the ‘on’ position for the battery to charge.
This connector should only be used with LiPo battries.
Checking Your Bluetooth Amplifier PCB
Carefully check the following before you connect the power:
Check the bottom of the board to ensure that:
 All holes (except the 3 large (3mm) holes in the corners) are filled with the lead of a component or wire.
o This excludes the LED2 terminals if no external LED is fitted.
 All these leads are soldered.
 Pins next to each other are not soldered together.
Check the top of the board to ensure that:
 The LiPo battery (if used) connects to the board where it is labelled ‘CON2’ and the red wire is next to the
adjacent PCB mounting hole.
Bluetooth Amplifier
Operating Instructions
What is the LED indicating?
Flash pattern
Single flash every 5 seconds
Connected, no music playing.
Double flash every 5 seconds
Connected & music playing.
Brief flash 4 times a second
In pairing mode, waiting for a phone to connect.
Longer flash (on for more time
than it is off) 4 times a second
Link lost. Waiting for a phone to connect or if the link was lost due to the
phone being out of range the Bluetooth amp can be switched off and on
and will pair again with the phone.
The phone is temporarily out of range of the Bluetooth amp. If music was
playing it is likely that the phone will have paused it. Bring the two
devices back in to range and resume the music. If the link is lost for more
than a minute then it will show link lost (as above).
What do the bleeps indicate?
Three notes ascending in
Device powered on.
Double beep
A new device has been successfully paired.
Triple beep
The Bluetooth link has been lost, bring the phone closer to the amplifier.
Quadruple beep
The battery is running low. Plug into the USB port. This beep will continue
to sound every 2 minutes until the battery is completely flat and the
device shuts down or the USB power is connected.
Pairing Process
To pair the Bluetooth Amplifier to a device (provided it is not already paired), use the devices Bluetooth settings
menu to search for new Bluetooth devices. The Bluetooth Amplifier will appear as ‘KITRONIK AMP’ followed by a 5
digit unique ID specific to the particular unit being used.
To change to another device the current device requires ‘un-pairing’. Again this is done from the devices Bluetooth
settings. Once complete the Bluetooth Amp automatically enters pairing mode again.
I the Bluetooth Amplifier is powered down and back up it will automatically connect to any Bluetooth device
previously paired to in range. If there are none in range it will automatically entering pairing mode.
Bluetooth Amplifier
Designing the Enclosure
When you design the enclosure, you will need to
 The size of the PCB (right).
 How to mount the speaker (below).
 Where the power switch and LED will be located.
These technical drawings of the amplifier PCB and
speakers should help you to plan this.
All dimensions in mm
5W 4 Ohm 65mm Full Range Speaker
20W 8 Ohm 100mm Full Range Speaker
Mounting the PCB
to the enclosure
The drawing to the
left shows how a
hex spacer can be
used with two
bolts to fix the PCB
to the enclosure.
Your PCB has four
mounting holes
designed to take
M3 bolts.
Bluetooth Amplifier
How the Bluetooth Amplifier Works
Speaker 1
Power Switch
LiPo Charger
Speaker 2
Indicator LED
(Off Board)
Bluetooth Module
At the heart of the Bluetooth Amplifier PCB is a Bluetooth Radio module. This performs a number of tasks:
Provides and manages the Bluetooth radio connection. It also has the aerial built into it.
Decodes the audio signal from the radio connection and outputs this to the amplifier circuit.
Drives the Indicator LEDs (on board, plus optional off board LED). These are used the display the current
mode, such as ‘pairing’.
Supplies charging circuit for a LiPo battery.
The audio output from the Bluetooth Module is fed into the 3W amplifier circuit. This uses a PAM8008 amplifier IC
which delivers 3W across two channels and contains a number of features to make the circuit simple and compact.
The device automatically reduces the volume to prevent distortion and offers over temperature and short circuit
The amplifier circuit is setup to have a fixed gain (or amplification) and the output volume is controlled by the
Bluetooth Module. This is adjusted by altering the volume on the Bluetooth device to which it is connected.
The circuit can be powered from either (or both) a micro USB power supply or LiPo battery. The power switch turns
the power to the whole circuit fully off. This therefore needs to be in the ‘on’ for the battery to charge, though the
circuit automatically enters a low power mode when not in use.
Online Information
A copy of this product information is available to download from:
This kit is designed and manufactured in the UK by Kitronik
Every effort has been made to ensure that these notes are correct, however Kitronik accept no responsibility for
issues arising from errors / omissions in the notes.
 Kitronik Ltd - Any unauthorised copying / duplication of this booklet or part thereof for purposes except for use
with Kitronik project kits is not allowed without Kitronik’s prior consent.
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF