DIY Digital Effect Pedal Platform Review: The Top 9

9 DIY Digital Effect Pedal Platform List

To start researching on DIY (do-it-yourself) digital  effect pedal for the next project, let’s see the list first. Take a look at some popular platforms to compare their specifications and prices, here are some:

1. UNO – Electrosmash’s pedalSHIELD UNO
2. MEGA – Electrosmash’s pedalSHIELD MEGA
3. DUE – Electrosmash’s pedalSHIELD DUE
4. Electrosmash’s Pedal Pi
5. Openmusiclabs’s Stomp Shield
6. Hoxton OWL
7. Axoloti
8. SlackDSP
9. Deepstomp

UNO – Electrosmash’s pedalSHIELD UNO

This stomp box platform is based on Arduino UNO. It mploys the built-in 10-bit ADC for the audio input and two 8-bit PWM for producing 16-bit output. The output stage includes a low-pass filter at 5 KHz cut-off frequency. The board implements a second order of active filter using with op-amp. The arduino UNO is an 8 bit AVR microcontroller runs on 16MHz clock. On the other hand, with only 2KB of RAM there would be very small space for delay-line based effect. With such low frequency cut-off of the output, we can say that this pedal could only produce a low-fidelity. The total price to build the complete working stomp box will be the shield price plus the UNO price. So, the total price will be around 61 USD (39 USD shield + 22 USD Arduino UNO).

MEGA – Electrosmash’s pedalSHIELD MEGA

The pedalSHIELD MEGA is similar to the pedalSHIEL UNO, but it employs Arduino MEGA as its core. The RAM capacity is 8KB, and it has OLED display for better control visualization. The input and output stages is the same with UNO version, so the sound quality would be similar. The cost of the shield board is 59 USD, and the Arduino MEGA board is 38 USD). As a result, the total price to build a working stomp box will be about 97 USD.

DUE – Electrosmash’s pedalSHIELD DUE

This pedal shield model is the most advanced platform from Electrosmash. It employs Arduino board as its core, because of the powerful core of the Arduino DUE. This pedal has three programmable potentiometer for the parameter controls, a mix switch, and a programmable switch. The Arduino DUE has 32 bit SAM3X8E ARM Cortex M3 microcontroller. It runs at 84 MHz, with 96KB of RAM  and 512 KB of Flash memory. The input and output conversion is better than the previous Arduino based shields, but unfortunately it employs only the built in 12-bit ADC and DAC. As conclusion, it would still be considered as low fidelity output.

PedalSHIELD DUE uses double channel for both ADC and DAC to increase the reading range. However, in my humble opinion, it would be useless in increasing the resolution. I think the reading of both channel of the ADC will result in the same bit changes. Consequently, it’s nothing more than doubling the single channel reading or writing. Similarly, writing both DAC will be the same, no resolution improvement at the result. It should have powerful computation resource for implementing many type of digital effect. Unfortunetely, the output resolution would be only 12-bit (please correct me if I’m wrong in deducting its final resolution). The price to build the complete stomp box will be around 93 USD (53 USD shield + 40 USD Arduino board).

Electrosmash Pedal-Pi DIY Digital Effect Pedal

The most powerful stomp box platform from Eelectrosmash should be Pedal-Pi. On the other hand, it’s really-really unfortunate that it has only 12-bit A/D converter. Using pi-zero board as the core, it has very powerful 1 GHz ARM11 core with 512MB of LPDDR2 SDRAM. The booting time for Linux operating system might be unsuitable for live performance. This can be painful when it need fast restart from power failure in a live setting.

I think it might be fine for studio recording if it has at least 16-bit codec for input-output conversion, but unfortunately it doesn’t. The cost to build this stomp box will be 65 USD for the shield and 5 USD for the Pi-Zero. In other words, it’s only 70 USD in total cost for 1 GHz processing core!  This has an incredible processing power  for very low cost but sorry to say,  not acceptable. Moreover, the low fidelity of 12-bit audio conversion make the power of Pi-Zero useless in generating high fidelity audio output.

Openmusiclabs’s Stomp Shield

Stomp Shield is an Arduino shield from openmusiclabs (dot com), works with Arduino Uno and Duemilanove. It has analog level control for input and output. It also has analog feedback from the output to the input. In other words, it feed the 16-bit (from double 8-bit PWM) output of the Arduino back to its analog input. It also has analog mix control that adjust the proportion between the original signal and the processed signal. The digital control is done through a rotary encoder, but unfortunately there is no display. So the operation modes or states of the operated menu would never be shown. However, the input conversion is done by the Arduino analog input, which has only 10-bit resolution. To build this stompbox, the total price would be around 91 USD. This total price comes from the 69 USD for the shield plus 22 USD from the Arduino UNO).

Hoxton OWL

This pedal is sold in completely built unit, but as being open source, the schematic diagram of the hardware and the source code of the software are available. The hardware specification can be considered as high-end, as shown in the list below:

• Powerful microcontroller:
  • 168MHz 32bit ARM Cortex M4
  • 192KB RAM, 1MB Flash memory
  • Integrated DSP, FPU, DMA
• 8kHz to 96kHz sampling rate
• More than 3000 instructions per sample @ 48kHz
• 1MB external SRAM
• 16/24 bit codec
• Stereo in/out
• USB MIDI
• 4 assignable control knobs
• Bypass foot switch
• Expression pedal jack
• Assignable illuminated pushbutton

Looking at the specification, this pedal should be capable of implementing high-end effects such as vocal-guitar harmonizer or vocoder. Despite its high-end feature, this pedal is sold only for 239 GBP or about 323 USD (at the time of writing this article). It would be great option for implementing a priceless unique effect model. But only if you have the effect model in your mind that  is not available on the high-end effect market. Definitely not for general effect that is available on the market, as they are very cheap now.

Axoloti

Axoloti is a general DSP board that can be used to develop effect pedal. Unlike other platforms, the board is not so popular for effect pedal. However, it’s been very popular in DIY synth community. The core is based on STM32F4 series (ARM Cortex M4), and here are some of their specification:

• 168MHz STM32F427 microcontroller
• 24bit/96kHz capable stereo audio ADC/DAC (editor and firmware currently only supports 24bit/48kHz)
• 8MB SDRam
• 1/4″ stereo input jack (line level with up to 55 dB digitally-controlled analog gain)
• 1/4″ stereo output jack (digitally-controlled volume, DC-coupled)
• 1/8″ headphone jack (same sound as the stereo output, independent volume)
• MIDI input (5-pole DIN)
• MIDI output (5-pole DIN)
• Micro-SDCard slot
• Micro-USB device port
• Full size USB host port, supports USB-MIDI compliant devices. USB Hubs are not supported!
• DC input (7-15V, 2.1mm center pin, center pin positive)
• Solder pads for connecting potentiometers, faders, switches, LED’s… (16 signals, ground, 3.3V supply, 5V supply). All I/O is 3.3V signalling.

It’s a good platform for developing advanced effect pedal, but the price is relatively high, about 73USD. However, in my humble opinion the specs worth the price.

SlackDSP/SlackDSP_mini

SlackDSP_mini platform is published on github’s public repository, https://github.com/slackDSP/slackDSP_mini. It use dsPIC33FJ128GP804 as the core, and use WM8510 chip as the mono codec. Complete hardware and software is published in the repository. For the specification, please look at the datasheet of the core and codec’s datasheet. This platform is not available as commercial kit product, so we can’t discuss the price. However, there is a demo video on youtube. And the link is provided in the repository page.

Deepstomp DIY Digital Effect Pedal

Deeptronic has developed an open platform for DIY digital multi-effect stompbox/pedal, called Deepstomp. The official website for deepstomp is https://www.deepstomp.deeptronic.com, and you can find more information about developing a complete multi-effect there. In summary, here are some of the interesting features:

• 72MHz ARM Cortex M3 core, 20kB RAM and 64Kb flash memory (for program and non-volatile data)
• 15/16bit audio I/O
• Support single effect and multi effect mode.
• User interface management by the core firmware for easy effect development.
• Preset management by the core firmware.
• Chromatic guitar tuner support in the core firmware.
• Ready to use implemented effect: noise gate, compressor, distortion, tone control, and echo delay.

The complete kit price is 59 USD, but you’ll get free shipping worldwide. Moreover, the kit includes the enclosure box so you’ll get a complete ready-to-use multi effect pedal after DIY assembly. You can buy the Deepstomp KIT product here and see the demo video below: