Author Archives: Nigel Redmon

Biquad C++ source code

Posted on November 26, 2012 by Nigel Redmon

I don’t want to get into the business of teaching people how to code—there are a huge number of free resources available on the internet to that do that. But I’ll give a small taste for those trying to get … Continue reading →

Posted in Biquads, Digital Audio, Filters, IIR Filters, Source Code | 99 Comments

A wavetable oscillator—end notes

Posted on November 18, 2012 by Nigel Redmon

I wrote the wavetable oscillator code from scratch as I wrote this series of articles, using just the thought process I gave. Hence, no references to other articles on wavetable oscillators. The concept of a phase accumulator is fairly obvious; … Continue reading →

Posted in Digital Audio, Oscillators, Wavetable Oscillators | 13 Comments

A wavetable oscillator—the code

Posted on May 25, 2012 by Nigel Redmon

The wavetable oscillator code follows the basic structure of most audio processing blocks, with three types of functions: at the start: initialization—create the oscillator and its wavetables as needed: control—change the oscillator frequency, and pulse width for PWM every sample: … Continue reading →

Posted in Digital Audio, Oscillators, Source Code, Wavetable Oscillators | 27 Comments

A wavetable oscillator—Part 3

Posted on May 9, 2012 by Nigel Redmon

In Part 2, we looked at how to use subtables designed to cover one octave each, removing upper harmonics for each higher octave to avoid aliasing. Here’s a view of the nine wavetables for our sawtooth oscillator, with the starting … Continue reading →

Posted in Digital Audio, Oscillators, Wavetable Oscillators | 10 Comments

A wavetable oscillator—Part 2

Posted on May 8, 2012 by Nigel Redmon

From Part 1, we have an oscillator. But we need to broaden it to allow scaling of harmonic content based on pitch so that we have all the harmonic content we need at the low frequency end, and, as we … Continue reading →

Posted in Aliasing, Digital Audio, Oscillators, Wavetable Oscillators | 25 Comments

A wavetable oscillator—Part 1

Posted on May 4, 2012 by Nigel Redmon

There are many ways to make an oscillator. Without looking for further motivation, I’ll propose a wavetable oscillator. Wavetables are a fairly obvious extension of the general playback of digital audio. Such oscillators are easy to understand, and their extreme … Continue reading →

Posted in Digital Audio, Oscillators, Sample Rate Conversion, Wavetable Oscillators | 5 Comments

A wavetable oscillator—Introduction

Posted on May 3, 2012 by Nigel Redmon

Years ago, Cristoph Kemper told me how the Access Virus came to be. He had coded a filter on a DSP and wanted to test it. Of course he needed an oscillator, so he coded that…pretty soon he had a … Continue reading →

Posted in Digital Audio, Oscillators, Wavetable Oscillators | Leave a comment

Convolution—in words

Posted on March 5, 2012 by Nigel Redmon

Convolution is a convoluted topic—and that’s what it means (convoluted, from Merriam-Webster : “Extremely complex and difficult to follow. Intricately folded, twisted, or coiled.”). Really, it’s more difficult to explain why you would want to use convolution than it is … Continue reading →

Posted in Convolution, Digital Audio, FIR Filters, Impulse Response, Reverb | Leave a comment

Biquad formulas

Posted on January 2, 2011 by Nigel Redmon

For fixed filters, we can plug biquad coefficients into our programs. But often, we need to calculate them on the fly, to user settings or changes in sample rate. As a companion to the biquad calculator, here are the formulas … Continue reading →

Posted in Biquads, Digital Audio, Filters, IIR Filters | 48 Comments

A biquad calculator

Posted on December 20, 2010 by Nigel Redmon

Something useful: a biquad filter coefficient calculator… Continue reading →

Posted in Biquads, Digital Audio, Filters, IIR Filters, Widgets | 37 Comments