I mentioned this project in the post about the LED VU meter. This project followed shortly after my first speaker project, as making that setup had made me instantly want to be able to make my own amplifier circuit and speaker box. I did some very limited internet searching at the time, and I soon came across the link below. That initiated the first of a great many trips I would make to Radioshack over the years for the components they sell in those small bins in the back of the store. I bought my first breadboard, which is the massive starter one you can buy that is really way larger than you could possibly use for your first few projects. That’s the second link below. I also used the third link, which was my first dealings with datasheets for electronic components, because there were still questions as to how the LM386 IC worked past what was explained in the tutorial.
http://sci-toys.com/scitoys/scitoys/computers/solderless/ic_amplifier/ic_amplifier.html
http://www.radioshack.com/product/index.jsp?productId=12165713&locale=en_US
http://www.ti.com/lit/ds/symlink/lm386.pdf
Just to clarify for those who have never worked with a LM386, but they will always clip and distort the sound if you adjust the gain up as high as you can, and at a great deal of volumes less than that. It’s not a very high quality chip for an audio perspective, but it is a fundamental learning tool that is readily available. Just saying, not audiophile quality by any stretch of the imagination.
If I remember correctly, the first circuit I made worked for a few seconds before getting really hot. I had to problem solve to figure out why things were getting so hot, and I soon established that the unregulated DC power supply I was using, which was from an old phone receiver we had laying around that said “9V” was in fact not putting out 9V. An amateur mistake, but one I battled for a number of years because I never fully understood these power supplies. I ended up going to 9V batteries since I was making a portable stereo, and that’s how the problem was identified. I then made up an entire second circuit so that I could amplify a stereo signal and once I got it all working I tried soldering it to a piece of PC board.
Now I don’t know what everyone else’s experience has been with soldering, but I can boast that every circuit I have ever soldered has worked in the end. Even this project, which at the time I was soldering together using a Cold Heat soldering iron that my dad gave me and was subsequently modified to be powered off a 5V 2A unregulated power supply, worked just fine when I got done. I was soldering directly to the IC without any sockets! I think this may be why I got into electronics so naturally. That’s not to say my soldering connections are top notch, but everything always seems to work out when I’m soldering.
So everything was soldered to a circuit board and working, and I had two speakers out of an old radio that were identical that I needed to mount in some enclosure. This is where things got ridiculous. I decided that I did not want to paint this one, so I cut out 1/8″ MDF pieces for the front and back, scrap wood pieces for the sides, and screwed it together using drywall screws. Now for some reason the second best way to cover a speaker box at the time was to glue on an old shammy for the front and try the same with an old sock elastic for the back panel? I think the idea came from how I had seen speakers covered in carpet, and this was my amateur idea of doing the same thing. Needless to say, it turned out looking as bad as the idea originally sounded. But I was quite happy with it. I then hot glued the speakers into the front face (no screw holes available) and slid the electronics inside. My final touch was using small pieces of cut plexiglass that were laying around for the top and bottom of the box. I figured that way I could show people that I made the electronics inside…I can’t imagine what else they would have thought about it. I mounted a switch and a 3.5 mm female connector in the top part and hot glued that piece on too.
This was my first experience with packing electrical components, and at that point I had a moment of clarity that was along the lines of “crap, what do I do when the battery dies?” I had sealed everything with no easy way to get inside without ripping things to pieces. Since it was already done and working I let it go, but that started my long standing dedication to serviceable project designs. But as far as this project goes, I was just proud I made a device from scratch that amplified music by myself. A truly great project.
TSouth Projects 