About 7 years ago I "accidentally" made a very lunkheaded, brute-force tremolo effect unit with an Arduino and a LM386 module. This was some Neanderthal electronics, with the Arduino cycling power to the LM386 module. Here's the original videos from back then:
"Finished" version: https://www.youtube.com/watch?v=9FoRHpJfV2Q
Original test unit: https://www.youtube.com/watch?v=EhW_YtAiELI
Over time, folks have asked how it was made, so I figured I would cover how to build a simplified version of it.
This walkthrough will be more like the original test version I made, as seen at :27 secs into the video. This was my very first tutorial, made earlier this year, so it's quite sloppy, but you should be able to follow along.
As I said, this is Neanderthal electronics, very dumb and brute-force. This is not how these components are meant to be used, and I can't guarantee you won't damage anything. I also assume you have a basic understanding of electronics and Arduinos. This is a fun project, but proceed at your own risk. Now let's break something!
PARTS
- An Arduino Uno, or similar
- A breadboard
- An LM 386 module (or roll your own if you know how)
- A 10k potentiometer
- A guitar jack. This one is good for breadboarding, but you can wire up whatever jack you have
- A speaker
- Four male-to-female wires
- Eight male to male wires
ARDUINO CODE
If you're familiar with Arduino, you know that a Blink sketch is one of the first programs you'll encounter. The program tells the Arduino to cycle power on and off, to an LED, making it blink. You can also use a Blink sketch to cycle power to other low-power items. Like an LM 386.'
We'll use a variation of the Blink sketch called Analog Input. This sketch is available in the Arduino IDE, under FIle -- Examples -- Analog -- Analog Input
This sketch adds a potentiometer to the Blink code, so you can control the length of the power cycles with the turn of a knob. A lot of what you need to know can actually be gleaned from the comments at the top of the code - but instead of an LED we’ll be blinking an LM386 module
You can keep the code as-is, and use pin 13 to cycle power. I'm changing it to pin 9 here because pin 13 also blinks the onboard LED, I believe.
I'm also designating a set length for "off," or "LOW," so my knob will only affect how long the power stays on. In my original design, I had two potentiometers, one to control the length of On, and one to control the length of Off. Here I'll set the off cycle to remain at 100 milliseconds just so we hear an obvious stutter effect. Feel free to experiment with it.
Upload the code to your Arduino, then disconnect the Arduino from your computer and keep it powered off while you continue building.
ASSEMBLING THE PARTS
Connect your guitar jack to the breadboard. If you're using one like this, the front legs go into the blue ground rail. If you have a more typical guitar jack, then SLEEVE goes to ground and TIP goes into a breadboard socket of your choice.
Next, get your LM 386 module and four male-to-female jumper wires
The two GROUND pins get wired to the blue ground rail.
The IN pin connects to a socket in the same row as your guitar jack tip wire. With my jack, it goes here.
VCC (or POWER) connects to an empty socket on the breadboard
Next, grab your Arduino and the male-to-male jumper wires. Connect the 5 volt OUT pin to the red power rail, and the Ground pin to the blue/ground rail.
Connect your Blink pin -- pin 9 in my case -- to a socket in the same row as the LM 386 VCC power wire
Connect the Potentiometer to the breadboard like so, with each leg in it's own row of sockets.
Connect that top leg to the blue ground line, the bottom leg to the red power line, and the middle leg to A0 on your Arduino.
When I say top, middle and bottom, I'm simply referring to how it looks from the perspective in this video.
Connect your speaker to the LM 386 Module
Connect the power and ground lines on the other side of the breadboard
Plug in your guitar
Power up your Arduino, using your computer, a usb power brick, or the Vin pin if you're familiar with doing that.
And now enjoy the sloppy, dirty, quasi tremolo effect!