Guitar Pedal Hack via Manufacturer’s Shortcut

modded guitar pedal

There seems to be no shortage of manufacturers that cut costs by using similar components across a wide range of products. This isn’t necessarily a bad thing though, since it makes it easier for someone with some know-how to quickly open up the product and figure out how to get more use out of it. [Lewin] noticed some peculiarities on the PCB of his EHX Screaming Bird guitar pedal, and used a manufacturer’s shortcut to turn this treble-boosting pedal into a flat booster.

Once [Lewin] removed the case, he noticed that there were some unpopulated pads on the PCB. Additionally, the potentiometer was labelled as 10k, but a 100k was actually installed. These were indications that something was awry, so after poking around on the internet, [Lewin] now believes that the same PCB was used to make at least three different effects pedals with similar internal structures.

The Screaming Bird pedal was a little harsh for [Lewin]‘s taste, so he changed out some capacitors on the board to get it closer to the flat booster. There are some other things that could be changed, but now he has a pedal that suits his needs much more appropriately, thanks to the manufacturer making only minor changes across a range of similar products. Historically, guitar pedals are pretty easy to modify, but it’s nice that the manufacturer of these has made it so much simpler!

DIY Foot Pedal Controller For Guitar Rig 5

DIY Modeling Software Control Pedal

Back in the old days, it took external guitar effects pedals to modify a guitar’s sound. As computer processing power has been growing at an exponential rate, software-based effects modelers have been becoming more common. [Matthew]‘s dad is running Guitar Rig 5 modeling software on his Lenovo tablet. Although it works well, it is a hassle to change effects and amp models while playing. That’s where [Matthew] comes in. He’s built a foot pedal controller so his old man can change up those sweet sounds on the fly.

Guitar Rig 5 has the ability to change presets with key presses. Even so, it would still be a hassle tapping a keyboard while playing, whether it be physical or on-screen. Since an Arduino-compatible board with an ATMEGA32U4 chip can be used to simulate an HID device, [Matthew] decided to use one as the basis for his project. Standard push buttons mounted in a project box indicate to the microcontroller which keyboard commands to send to the tablet. There are 4 buttons for 4 presets on this build but any number can be used. When a button is pushed, the associated keyboard command is sent to the tablet via a USB cable and Guitar Rig 5 responds to that command by changing the preset. And just so you know where you are, an indicator light adjacent to each button shows which preset is current.

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An Opensource Arduino Guitar Pedal

pedalshield

If you’re a guitarist, or know a guitarist, you probably know just how many guitar effects there are out there — but what if you could design your own effects?

[J Rodriguez] has just released his opensource Arduino guitar pedal shield, dubbed the pedalSHIELD. He designed it as a platform to learn about digital signal processing, effects, and synthesizers — without needing an in-depth knowledge of electronics or programming. It allows you to design your own effects in C/C++, or download from his own library online. Some of the downloadable presets include an octave pedal, reverb pedals, delay pedals, and even distortion pedals!

The pedal features three programmable potentiometers, two main switches, and the foot pedal switch. The shield plugs directly into an Arduino Due, and you can find all the schematics here and the parts list here. It was completely designed in KiCad which is an open source electronics CAD design suite.

Take a listen after the break to hear the pedal in action!

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Improving A Cheap Guitar Pedal

pedul

If something doesn’t suit your needs, just change it. That’s a motto we live by, and it looks like [Doug] took up the same creed when he modified a cheap effects pedal.

The victim of [Doug]‘s soldering iron is a Danelectro BLT Slap Echo – a tiny, cheap pedal in Danelectro’s mini ‘food named’ pedal series. Stock, this pedal’s slap back echo is set to a fixed amount of time. [Doug]‘s mod changes that.

The mod consists of desoldering a single SMD resistor and replacing that with a 50k pot [Doug] had lying around. After mounting the pot between the two stock knobs, the new and improved pedal had a variable length echo. There are a few more mods possible with this pedal – changing some of the resistors on the filter for a better sound, or even connecting the rate pot to a wah-style rocker pedal for some wobbly Echoplex or Space Echo action.

You can check out [Doug]‘s gallery of pics here.

Homebrew guitar tuner also includes MIDI out

A few years ago, [Frédéric]‘s brother in law wanted a guitar tuner for Christmas. Instead of going out and buying one, [Frédéric] broke out the soldering iron and built one from scratch.

[Frédéric]‘s tuner is built around an ATMega168 uC on a Real Bare-Bones Board with an LM386 amplifier. The display is a standard 20×2 LCD character display, and the interface is torn from the pages of stomp box schematics with a very hefty foot switch.

Detecting the frequency of a note played into [Frédéric]‘s tuner involves a fair bit of math. To measure the frequency, the Arduino samples the waveform coming from the input jack. This signal is delayed for a fraction of a second and the area underneath the real and delayed waveforms is measured. This delay slides across the original waveform until the area between the real and delayed samples are minimized. At that point, delayed wave form will be exactly one cycle behind the real signal, and the cycles per second can be calculated. It’s called the YIN algorithm, and you can read more about it here.

Since [Frédéric] already knew the exact frequency being played into the tuner, he figured it would be trivial to add a small analog audio to MIDI converter. This feature (as shown in the video after the break) turns the sounds from a guitar into MIDI notes. It’s monophonic and probably a little superfluous, but still very cool.

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Putting guitar pedals in a web page

Only half of playing guitar – according to a few musician friends of mine – is moving your fingers up and down a fretboard and banging out some chords. The other half is the artistry of mastering your tone, usually through amp settings and stomp boxes.

Effects pedals – little boxes of electronics that go between the guitar and amp – are able to amplify and distort a guitar’s output, add reverb and delay, and even filter the tone via a wha or envelope pedal. These pedals can be simulated in software, but we can’t believe that they can now be emulated completely in JavaScript.

Pedalboard.js is a project put together by [dashersw], and aims to put a slew of pedals ‘in the cloud’ and turn editing and effects board as easy as building a web page.

The project is built around Webkit’s W3C audio API, allowing this virtual pedal board to work in Chrome, Safari, and other Webkit-enabled browsers. Pedals are programmed as nodes, each configurable to have and input, output, or analyzer that is able to modify the gain, wave shape, or filter of anything received by the line in on your computer.

Thee is a small demo of Pedalboard.js available here with a pre-recorded guitar track feeding into a few stomp boxes. It’s a pretty cool idea if you’d like to play around with a few guitar effect, but we can’t wait to see this bit of JavaScript implemented by effects pedal manufacturers allowing us to try before we buy.

Playing with DSP and building a guitar pedal

Building guitar pedals has come a long way from hooking up a few transistors and building a simple boost circuit. [Cloudscapes] has been working on a Anti-nautilus auto glitch, auto repeat pedal, and if you’re looking for something that sounds like a spaghetti western soundtrack skipping on a record player, we couldn’t think of anything better.

[Cloudscapes] was already familiar with 8-bit AVRs, but when doing real-time audio sampling, a more powerful microcontroller was in order. He turned to the MikroElektronika MINI-32 board for development purposes. This small board fits a PIC32 microcontroller into an easily breadboardable DIP-40 form factor, perfect for playing around with some very capable hardware.

For the DAC, [Cloudscapes] had some experience with the 16-bit PT8211, but finding a good 16-bit ADC in a convenient package was a bit of a challenge. He eventually settled on the 12-bit MCP3201 ADC, more than enough for a pedal that is supposed to sound lo-fi.

After [Cloudscapes] got a few boards made, he started on his DSP adventure. Unfortunately, the initial code used unsigned 16-bit words to represent each sample, meaning every time the loop repeated it would start at 0 and produce a short pop in the speaker. After a week of debugging, [Cloudscapes] realized signed integers are a much better data format for storing audio data and got rid of the problems plaguing his project.

Now [Cloudscapes] has a wonderful DSP dev board, perfect for making new and strange guitar effects. After the break you can listen to a demo of what the Anti-nautilus pedal actually does, and we’ve got to say it sounds great.

Thanks [Chris] for sending this one in.

[Read more...]

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