Why add an audio input?
Megaphones are good for getting noisy, especially at street parties, on bike rides, and at protests. And there's no shortage of reasons to get with your friends and organize a protest. Megaphones are great, but you're limited to amplifying only what you can put into a microphone. What about music?
So with a few minutes of work you can add a new dimension to your protests and critical mass bike rides. You can blast music.
What you'll need:
+ a megaphone (got mine for $10 at harbor frieght)
+ an old pair of earphones (old broken pair)
+ soldering iron and solder
+ electrical tape
+ scissors or knife
In this project you'll snip your megaphone's mic wires, snip your earphones, and then solder your earphone jack onto the mic wires.
Step 1: Open Up Your Megaphone
Step 2: Snip Some Wires
Strip a little bit of the plastic sheathing from each of the four wires: red & black on the mic and two wires that go to the earphone jack. You want to have a little bit of the metal exposed, so you can solder them together.
Sometimes the metal wires inside of earphones are coated in some kind of insulation. You can tell if they are a little colored (red or green, usually). Take a match or lighter to the exposed metal to burn off the insultation. It should burn pretty quickly, like a fuse. You need to do this to make sure the wires make a connection when you solder them together.
Step 3: Connect the Wires
Next you'll want to connect the jack to the microphone wires. On my megaphone I needed to connect the ground to red and the "live" to black. If that doesn't work for you, switch them. I just tried one and then the other.
Twist the wires together and then either solder them together or wrap them with electrical tape.
I actually got frustrated working with such short wires, so I took a small piece of the earphone wire and soldered it to the mic to extend the wires (see the photos).
Step 4: Patch Up the Case and Close It Up
Now your megaphone has an audio input. Hook up an mp3 player and blast some music. The microphone should still work too. You can even sing along to the music while you play it.
If you're having trouble getting it to work, make sure your wires are making connections. There isn't much else that could go wrong.
Step 5: Troubleshooting & Future Improvements
A cooler improvement would be to get a few of these and add FM recievers in the place of audio jacks. Then use one of those local area FM transmitters that people use in their cars to wirelessly send out music to all the megaphones nearby. It would be neat to have a set of megaphones that are all wirelessly broadcasting the same audio.