DIY HeadPhone Amplilfier

Background

I have always been interested in building something like this since my second year at university. But apart from repairing small things like re-soldering a power cord, my adventures down this alley have normally resulted in failure. The most memorable was my attempt at building an FM transmitter from an internet schematic (I can’t even tell what was wrong with this, it just did not work). Recently though, I was encouraged by my “success” in replacing the bulb in my flashlight with LEDs. I put success in quotes because there was no notable increase in the illumination from the torch but it was at least not worse than it was before. So I count it “success”…….. 🙂

This project came back to the forefront a few months ago when I decided to learn the bass guitar but as you might expect, this was not kind on the ears of the people who had to listen while I slowly and painfully attempted to get to the skill level of the likes of Fred Hammond. So I thought this was a great opportunity to convince my wife why it was necessary for me to get a headphone amplifier 😉

Assembly

And so the journey begins. I did quite a bit of research on my options (to build or to buy??). I ended up striking the middle ground by buying this kit off eBay and try to recreate my recent success in the field of DIY electronics. It basically contains a printed circuit board and all the parts needed (that was another reason I got a kit as opposed to buying individual parts. It is hard to get exact parts locally and as a beginner it is not easy to substitute parts). Anyway, 6 weeks later the package arrived and I dove into the construction.

The first thing I noticed was that the schematic referred to a  pair of capacitors which were not in the package.

Kit as shown on eBay....notice the 2 blue capacitors beside the board?

I decided to put it together anyway even though all internet references to the project showed that a couple of capacitors should be in the mix.

Other than that the process was mostly without event. But it was a huge learning experience with regards to soldering. For instance, I don’t know the differences between the type of solders (need to read up on that shortly) but the one that was included in the kit had a tendency to “blot up” more than the one I had. It was as if it was harder to melt and I had to be making a special effort to get clean, neat solder-points. When I started using the one I had before, as soon as I touched it with the soldering iron it just melted and it was like it formed the perfect shape all by itself (as opposed to spreading out all over the board). Also, the opamp chip should be removed from socket before the socket is soldered….it will burn :-D.

Pics of the process and the finished product can be seen here.

I carved a housing for it out of an extra power brick which I had lying around in a box. This was quite a challenge though because I didn’t have any of  the tools to make the holes or properly mark out the spots to be cut. As you can see it wasn’t a total disaster.

Conclusion

Apparently the capacitors weren’t needed as the completed amp worked perfectly without it. As a-matter-of-fact when I added some capacitors of values which some other sites were recommending for their projects, it sounded significantly weaker.

So, as is, the amplifier sounds loud and clear with even my cheap/free BB earbuds and does enough to let me hear the guitar without disturbing anyone else. Overall this experience is worth far more than the $25 I spent on this project.

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