Introduction: Post-Apocalyptic Amplifier

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In the case of an apocalyptic event, and you don't have an amplifier because Immortan Joe took all the amplifiers, then you need to know how to build yourself an amplifier!

In this Instructable, I'll guide you through the process of constructing an amplifier from scrap components, and show you where you can salvage the material you need.

This amplifier can be powered by a 9V battery or DC power, and the size of it makes it a wonderful travel amp.

Step 1: Watch the Video!

Click here to view on YouTube

Check out this quick video to see the amplifier working and hear how it sounds! It also guides you through the steps below from start to end.

Step 2: What We'll Need...

I'll be showing you where you can scavenge most of these components in the steps to follow.

Here's the list of components we'll need:

  • An LM386 amplifier chip
  • A 220uF electrolytic capacitors
  • Two 10uF electrolytic capacitors
  • A 47nF capacitor (usually film)
  • A 1nF capacitor (usually ceramic)
  • A 10ohm resistor
  • A 9 volt battery connector
  • A DC Jack - this can be switched or not switched
  • If the DC jack is not switched then, you'll need a SPDT slider switch
  • A push button
  • Two 1/4" mono panel jacks
  • A 20k ohm log taper potentiometer
  • A small paper protoboard
  • And a tin can that fits all the components.

Where to buy

Soldering gear:

Testing gear:

Step 3: What's Inside the Tin Can?

Here's a simple outline of how we're going to wire our components in the tin can.

We'll be building an amp module using the LM386 chip, then we'll wire in the input and output components, followed by the power supply components to the amp.

Step 4: Input/Output Components

First we'll be taking a look at the input and output components.

We take a mono jack and wire it up to our 20k ohm potentiometer as input - this will let us adjust the volume of our amp. The other mono jack will come out the amplifier as output.

Salvaging tip: I salvaged these components from an old karaoke mixer. Just be sure to use a log taper potentiometer and not a linear taper one. Usually the volume knobs will be log taper and tone knobs will be linear.

Step 5: Power Components

Next we'll look at how we wire up our power source.

Since our amplifier can be powered by a 9V battery or from the DC jack, we will need a mechanism that disconnects the battery power source once a DC jack has been plugged in.

If your DC jack is switched (3 prong) then refer to the first diagram.

  • Switched DC jacks have two prongs that are closed when nothing is plugged into the jack, but opens once something is plugged in. This extra prong is called the "connect terminal" (labelled "C" in the diagram).

If your DC jack is not switched (2 prong) then refer to the second diagram.

  • We'll be using a SPDT slide switch (3 prong switch) to manually flip between the power sources.

Salvaging tip: if you remove the top piece of a dead 9V battery with a pair of pliers, you can use it as a 9V connector.

Step 6: Amplifier Module

We'll be using the LM386 operational amplifier chip. There are many other op amps that can be commonly found in scrap electronic boards that can work just as well, but you will need to refer to their own datasheet on how to power it.

The first diagram here shows how to wire up our amplifier chip. The video attached above explains the functionality of every individual component in detail, but if you'd like to just get it done, then read on!

Salvaging tips:

  • The capacitors and resistors used for this build are very common, you can salvage them from scrap electronic boards. Look for electrolytic capacitors that are rated 10v or higher.
  • If you're ever having trouble finding a 47nF capacitor, I have always found at least one of them inside a CFL lightbulb. You can pry open the base of the lightbulb with a small screwdriver (they will be labelled with 473 or 47n).

Step 7: Soldering the Amp Module

So once you have all your amplifier components gathered, start organizing them on the protoboard and bend the pins on the back to hold them in place.

Hold the module in place with a piece of sticky tack while you solder down the components.

I also made a common ground point in the corner of the board, but will come back to solder the ground connections once I plug in all the other components.

Step 8: Attach All Components

We can take our input, output and power connections and hot glue them onto the protoboard as well.

And we'll use loose wires to finish the connections and make sure that all ground connections go to the common ground point.

Step 9: Choose a Container

Next we'll have to choose an appropriate container to fit everything. I'll be using this Fisherman's Friend tin.

After we know how we're going to place our components, we'll mark down where we need to make a few holes.

Step 10: Cutting the Container

The most effective way I found to cut this tin can was to first cut a small piece of scrap wood that fits inside the can.

After that, we can place the can on the piece of wood for support.

I then took a nail to punch a hole in the center of the marking, and used a stepper drill bit to drill out the hole.

Step 11: Fill the Container

If our container is made of metal, we'll have to tape up the insides of the container with some electrical tape so that the metal doesn't short anything unintentionally.

And then we'll just place everything into our case again and hot glue it in place.

Step 12: We're Done!

Close it up, and we're done building the amplifier!

I added a plastic piece around my potentiometer to hide the sharp edges of the cut in the container. I also found a small plastic red lid that fit nicely on the power button.

Step 13: Finding a Speaker

Speakers can be found everywhere! I salvaged a Yamaha 3 watt speaker from my old keyboard piano that I used for my MIDI piano Instructable.

Step 14: Making the Speaker Container

I simply measured out the dimensions of a box that wraps the speaker, and included a bit of extra space so that I could store the cable inside the box. I also covered the front of the speaker with a piece of cloth, and cut out a hole in the front of the cardboard box. Then I attached the speaker with some nuts and bolts.

I then took a cut open 1/4" mono cable and soldered it to the two ends of the speaker.

After that, we can close up the box with a bit of hot glue and we're ready to give it a test!

Step 15: Give It a Test!

Plug it in and give it a test! Check out the video attached above to hear how this amplifier and speaker sounds!

If you liked this project, then don't forget to share it with all your musical friends.

This amplifier is going to be a prerequisite for some upcoming projects. So be sure to check back in next week to see some awesome things we can build with this tin can amplifier.

If you liked this instructable, then perhaps you'll like some of my other projects!

You can check them out at my YouTube Channel!

See you next week!