Four-Point (Three-Gradient) Linear Interpolation Extension for One Dimensional Data

Background In developing digital signal processor for Deepstomp (do-it-yourself digital multi-effect pedal platform), I have to optimize all computation in fix point math since the employed signal controller is just a cheap 32-bit processor with no floating point unit  (ARM Cortex M3 microcontroller). The most important effect especially for electric guitar is distortion effect, which can be simulated using sigmoid […]

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Deepstomp: Low-Cost High-Performance DIY Multi-Effects Pedal/Stompbox Platform

Introduction The advance of today’s digital electronics bring a new hopes for many things, because now there are many choices for low cost and high performance DSP microcontrollers. For example, a small board, popularly called “blue-pill”, is advertised in an online store for only US$ 2.25 (Figure 1.-upper part). It has 72MHz 32-bit processor core with some DSP instruction sets […]

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10 DIY Digital Stompbox / Effect Pedal Platforms Review

To start researching on DIY (do-it-yourself) digital  stomp box / effect pedal for the next project, let’s take a look at some popular platforms to compare their specifications and prices.  Here some of them in my list: Electrosmash’s pedalSHIELD UNO Electrosmash’s pedalSHIELD MEGA Electrosmash’s pedalSHIELD DUE Electrosmash’s Pedal Pi Openmusiclabs’s Stomp Shield Hoxton OWL Teensy Axoloti SlackDSP Sparkfun’s Proto Pedal […]

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Automatic Wah/Quack Effect Circuit with Attack and Decay Control

To get various characteristic of an auto wah/quack effect, we need a flexible control of  the envelope detection characteristic. Some playing styles need slow attack but fast decay,  but some others don’t. Employing the detector circuit presented in our previous article Envelope Detector Circuit with Separate Attack/Rise and Decay/Release Time Settings, here we present the improvement of the previous auto […]

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Automatic Wah/Quack Effect Using LED+LDR Controlled Band-Pass Filter

Introduction to Automatic Wah/Quack Effect Automatic wah/quack effect gives a similar effect with the manual version (reference [1]), but without the need of any pedal to manually control the frequency/tonal sweep. This automation is made possible by detecting the envelope signal of the instruments audio signal, and use it to control the filter to produce center frequency  sweep, producing audio […]

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Inductor-less Wah/Crying Baby/Quack Effect Using Operational Amplifier

A type of guitar effect pedal that produce “wah”- or “quack”-like sound, which is similar to the crying sound of  a baby is called  wah-wah pedal, or just  wah pedal. The effect is produced by filtering the musical instrument through a band-pass filter, which the center of its peak frequency is swept from low to high, mimicking  audio tonal transition […]

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Fold-Back Distortion: Producing “Phew” Effect Using Software and Hardware (Analog Electronic Circuit)

Introduction: What is Fold-Back Distortion? I was introduced to a term of  “fold-back distortion” in the past by an article from an old book which I forget what the title is, but the book contains schematic diagrams of many circuits collected from old publication of Elektor magazine (www.elektor.com). The article presents the circuit’s schematic diagram and how it works. I […]

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