If you know how to solder and plug some components into a breadboard, you have all the skills you need to build your own homemade guitar amplifier. It doesn’t have to involve any tubes or dangerous voltage. In fact, the design in this project is powered by a simple 9-volt battery and built only with parts that you can pick up today at an electronics store.

The design is based on the “Little Gem” amplifier circuit from runoffgroove.com. There are a lot of other great guitar circuits there for you to explore once you get the hang of it!

What you’ll need

9-volt battery

battery connector

Audio amplifier IC chip, LM386N

8 pin IC socket

220µf electrolytic capacitor

100µf electrolytic capacitor

0.047µf ceramic capacitor

0.01µf polyester film capacitor

10? resistor

5k? Audio-taper Potentiometer

25? Rheostat variable resistor

8? mini-speaker

mini toggle switch

¼” mono phone jack

breadboard

printed circuit board

solid core hookup wire

Get the schematic

The design we’ll be using is the RunoffGroove “Little Gem” amplifier and you can find the schematic drawing here.

If you have trouble reading this kind of schematic, flickr user cairn_idris has made a much more readable circuit drawing and posted it here.

Start plugging things in on your breadboard

First, let’s put in the socket for our IC audio amplifier chip. We want a socket so we’re less likely to break off the pins on the chip itself.

Place the socket so that it bridges the gap in the center of the breadboard (pic #1). The horizontal rows in the breadboard make connections, but the center ridge breaks them. So placing the chip over the gap will allow us to make connections to the pins without connecting the pins to each other.

Now you can put the chip in the socket. Make sure you notice the notch in the chip, it should be at the top (pics #2, #3).

I’m going to start roughly on the left side of the schematic and move left to right. The first thing we see is labeled “In." This will be our input. For a guitar amp, we want this to be our ¼ mono jack. We’ll have to solder some wires to it first. On a guitar cable plug, the signal is carried on the tip and the ground is the sleeve (pic #4).

When it is plugged into the jack you can see the tip touches the smaller contact that comes off the side of the jack. Let’s solder a signal wire (green) to that contact, and a ground wire (black) to the larger outer contact (pic #5).

Now, looking at the schematic, we can see that the input signal goes to a .01µf capacitor and then into pin 2 of our chip. If we look at the diagram provided on the back of the package the chip came in, we can see this pin is labeled “input.”

Using the breadboard, connect the capacitor to pin 2 and a new row. Then connect the input signal wire to that same row (pic #6).

Wiring the potentiometer

Next we should wire up the 5k? potentiometer. This is represented on the schematic by the squiggly line with an arrow pointing to it. The arrow itself represents the connection to the ‘wiper’ or the middle contact on the potentiometer. Solder a wire to the middle contact, and another wire to the contact to its right (pic #7).

Connect those wires to pin 8 (upper right) and pin 1 (upper left) respectively. On our chip diagram these pins are both labeled ‘gain’ so this will be our gain knob controlling the amount of fuzzy distortion.

The icon on the schematic that looks like an arrow pointing down represents a connection to ground. We will make the power and common ground the red and blue columns on the edge of our breadboard. Pins 3 and 4 should be connected to ground so use hookup wires to make those 2 connections on the breadboard (pic #8).

Powering up

We haven’t connected power to our board yet, but it will be a 9-volt battery. So the +9V on our schematic represents a connection to power, the red column. This should be connected directly to pin 6 (labeled Vs) and also connected to ground passing through a 100µf capacitor. These are directional so it’s important to connect them in the right direction. Looking at the ends of the capacitor, one should be a shiny metal and the other should not. The shiny metal end is the negative side so connect that to ground and the other to power (pic 10).

Note: I’m leaving the leads fairly long at this point as I might need them later when I make the more permanent circuit board.

Now there is only one more pin we need to make connections to, pin 5 labeled Vout. This is our output, which we will be sending to the speaker. This pin will make two connections, one goes through a 220µf capacitor to the rheostat (which connects to our speaker and ground), and the other goes to ground passing through the 10? resistor and the smallest 0.047µf capacitor.

Let’s make the connection to ground first. Make a connection from pin 5’s row to another row using the resistor. Then make a connection from that row to another new row using the capacitor. Finally connect that row to ground with a hookup wire (pic #12).

Now for the other connection, we start with the 220µf capacitor. Again, it’s polarized. The longer lead is positive, and the negative end is labeled with a stripe on the body of the capacitor. Connect the positive end to the row of pin 5, and the negative end to a new row.

We’ll have to solder some wires to the rheostat to make the rest of the connections. A rheostat is a lot like a potentiometer, but can handle much higher currents so it’s perfect for the amplifier output. The wiper (the arrow on the schematic) is labeled output (which is our speaker) so connect the middle contact to the positive lead from the speaker. The other contacts should be black wires for ground (both to the board and to the speaker) and a yellow wire that connects back to the capacitor coming out of pin 5 (pic #13).

The last step is to connect our battery connector to the power and ground columns (red and blue) and see if our amplifier works!