Velleman 3W Mono Amplifier

Amplifier Components

With the sort of tinkering I get up to, it is often useful to have a small amplifier on hand.  Couldn't resist when I saw this little kit on sale for $10.  It requires just a little soldering (34 connections in all) and it is recommended for this project that you insert a pointed tip into your soldering iron.  We will be soldering components onto a PCB so it is important to do a neat job with the soldering iron being careful not to short-circuit two pins by using too much solder.  The amp consists of a PCB, an IC, five capacitors, a diode and some terminal pins.  Beginning with the IC, the components are added one-by-one to the PCB and soldered into place.  The IC is soldered directly to the PCB and does not require the use of an IC socket.  Care should be taken not to use too much solder as the terminals are very close together and we don't want any short-circuits.  The amp consumer a maximum of 3W of power with corresponds to 500mA at 6V and will accept an input voltage of 6VDC to 15VDC.  I found an old 9V DC power supply supply that delivers 600mA which should be perfect for the job.  I cut the plug off this and soldered it to the power terminals of the amplifier making sure not to cross the positive and negative wires (a cheap multimeter can help with this).

Soldering the components

For the purpose of testing the amplifier, I used the same paper plate speaker that I built in a previous project (actually I had to rebuild the speaker because the old one was looking a little worse for wear).  This allowed for a direct comparison of the speaker performance first without and then with the added 3W amplifier.  Since this is a mono amplifier and because we have only one speaker, when connecting the 3.5mm stereo jack to the input terminals of the amplifier, the left and right channels were first twisted together.  The use of crocodile clips makes it quick and easy to connect the speaker and the audio source to the amplifier.  The insulation on the wires can be easily removed by using a lighter to burn the tips.  I must say, I'm pretty impressed with the results.  The amplifier gave the speaker performance a dramatic boost. In fact so much so that turning the volume up too much caused the speaker the reverberate to the point of distortion.  To be fair, it should also be mentioned that, when hooked up to a proper (higher quality) speaker, the amplifier delivered a clear, crisp sound (substantially better than that of the paper plate speaker - as you might expect) and good volume.  This is a very handy amp that can be used for a whole array of applications and at a (marked down) $10 price point at my nearby Radio Shack, I bought a whole bunch of them - can't go wrong!  Additionally, this project provides a good, quick exercise to brush up of your soldering skills.  This whole project should take no more than 30 minutes from start to finish.