This is a short guide describing how to use a 12V DC power supply with the Mono Amplifier project kit.

Step 1

Before you start it is important to ensure that the power supply that you choose is suitable for your project kit.  This application note has been written to explain how to connect the 12V switch mode PSU (power supply unit) shown left, to our Mono MP3 Amplifier project kit.  This kit will run off a voltage of between 4V and 15V, so a 12V PSU is suitable. Many of our kits run from a lower voltage so please check the PSU is suitable before attempting to connect it to your project.  

Step 2

  Cut the DC jack off of the power cable as this will not be required.  

Step 3

  Next, trim the insulation off the wire, then leave two ends that can be soldered into the PCB.  

Step 4

  Please check the PSU version you have before proceeding as there are two different plug types with different polarities! If the plug on your 12V 0.5A PSU looks like this one then the wire with the white stripe is the ‘-’connection.  This should be soldered to the corresponding pad on power connections on the PCB. This is also labelled ‘black’ on the PCB. The plain wire (with some text printed on it) is the ‘+’connection. This should be soldered to the corresponding pad on power connections on the PCB.  This is also labelled ‘red’ on the PCB. However if the plug on your 12V 0.5A PSU looks like this one then the wire with the white stripe is the positive ‘+’  connection. The plain wire is the negative ‘-’ connection. These should be soldered onto the corresponding pads on the PCB. If you are unsure which wire is which, you can double check by using a volt meter to check the polarity (if it reads a negative voltage the wires are backwards).  

Step 5

  This last point only applies to our Mono Amplifier. When the circuit is powered from batteries it didn’t matter which way around the two ‘input’ wires are connected. However when powering the circuit from the PSU it is important to connect these in a particular orientation, otherwise you will experience a lot of ‘mains hum’ from the speaker. The jack lead assembly supplied with the kit has two wires. Just like the PSU wires described above, one has a white stripe. This should be connected in the orientation shown in the picture to the left.

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