
Recent Posts
Archives
 January 2023
 April 2022
 November 2021
 September 2021
 April 2021
 October 2020
 January 2020
 April 2019
 September 2018
 August 2017
 May 2017
 January 2017
 December 2016
 September 2016
 February 2016
 September 2015
 January 2015
 March 2014
 January 2014
 October 2013
 June 2013
 May 2013
 April 2013
 March 2013
 February 2013
 December 2012
 November 2012
 May 2012
 March 2012
 January 2011
 December 2010
 November 2010
 July 2007
 March 2003
 February 2003
 August 2002
 January 1997
 November 1996
 October 1996
 August 1996
 July 1996
Categories
 Digital Audio (67)
 Aliasing (9)
 Convolution (3)
 Dither (7)
 Filters (24)
 DC Blocker (1)
 FIR Filters (7)
 IIR Filters (18)
 Biquads (12)
 Fourier (3)
 FFT (3)
 Fun Facts (3)
 Impulse Response (5)
 Jitter (2)
 Oscillators (12)
 Phase (2)
 Reverb (2)
 Sample Rate Conversion (10)
 Sampling Theory (6)
 Effects (1)
 Envelope Generators (5)
 Math (5)
 MIDI (2)
 Source Code (10)
 Synthesizers (9)
 Uncategorized (4)
 Video (7)
 Widgets (14)
 Digital Audio (67)
Category Archives: IIR Filters
A onepole filter
Here’s a very simple workhorse of DSP applications—the onepole filter. By comparison, biquads implement two zeros and two poles. You can see that our onepole simply discards the zeros (the feedforward delay paths) and the second pole (feedback path): We … Continue reading
Posted in DC Blocker, Digital Audio, IIR Filters, Source Code
40 Comments
Biquad C++ source code
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
87 Comments
Biquad formulas
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
The bilinear z transform
The bilinear transform is the most popular method of converting analog filter prototypes in the s domain to the z domain so we can implement them as digital filters. The reason we are interested in these s domain filters is … Continue reading
Posted in Digital Audio, Filters, IIR Filters
29 Comments
The digital state variable filter
The digital state variable filter was described in Hal Chamberlin’s Musical Applications of Microprocessors. Derived by straightforward replacement of components from the analog state variable fiter with digital counterparts, the digital state variable is a popular synthesizer filter, as was its … Continue reading
Posted in Digital Audio, Filters, IIR Filters
25 Comments
Biquads
One of the mostused filter forms is the biquad. A biquad is a second order (two poles and two zeros) IIR filter. It is high enough order to be useful on its own, and—because of coefficient sensitivities in higher order … Continue reading
Posted in Biquads, Digital Audio, Filters, IIR Filters
30 Comments