- Phase distortion synthesis
Phase distortion synthesis is a synthesis method introduced in
1984by Casioin its CZ range of synths, and similar to Frequency modulation synthesisin the sense that they are both built on phase modulation. Basically a sine waveis played, but by modifying the phase angle, the sine wave is bent out of shape.
Figure A shows how a sine wave gradually turns into a saw wave as the readout phase angle gets more and more distorted. Depending on whether a frequency counter x, is above or below the current distortion point d (the sharp knee in the phase angle insert) one of two equations must be solved:
if(x > d) return sin( x * d / pi); else return sin((x-d) * pi / (1-d) + pi);
Figure B is similar to A, only showing the development of a square wave instead. For x values below the first knee in the phase angle insert, the y values will vary rapidly between -3.14 and 0 resulting in the initial sharp rise of the square. Values between the first knee and the center knee all equals 0.0 resulting in the squares flat ceiling in the first half wave. At this point there is again a sudden rise in the phase angle up to 3.14, resulting in the "fall" of the square wave down to its flat floor at -1.0 where it stays until the frequency counter wraps around and repeats the process.
Other phase distortion patterns that are supported on the CZ range are impulse, half-sine and double impulse. The CZ synths also generate synchronised and windowed sine waves in order to emulate resonant filter sweeps.
Internally, phase distortion synthesis works by reading a sine wave table stored in memory. The
most significant bits of an initial linear frequency counter is under envelope control transformed into a secondary phase angle signal which is then used to read the sine wave. Depending on the wiring, the transform will change and a wide variety of waveshapes can be produced.
harmoniccoming into view.)]
The phase transforms are all assembled from piecewise linear functions under binary logic control and shows characteristic sharp knees (and for some transforms, even sudden jumps) as they move from minimum to maximum, where the frequency counters accumulator wraps around and starts over. The sharp knees are smoothened out by the roundness of the modulated sine wave and not too noticeable in the resulting signal.
Simulating a resonant filter
Figure 19 from the 1985 CZ-series patent shows how to emulate the variable resonance found in analogue voltage controlled filters:
* (a) The base frequency counter, wrapping around every period.
* (b) The resonance frequency counter at a slightly higher frequency, being reset ("or "synced"") when the base counter wraps around.
* (c) The resonance frequency counter used as a sine wave readout. "Note the nasty sudden jump at the reset!"
* (d) The inverted base frequency counter.
* (e) Multiplying c by d. "The sudden jump in" c "is now leveled out."
Casio made five different synthesizers using this method of phase distortion synthesis.
The VZ-1's synthesis method ("Interactive phase distortion") includes
Frequency modulation synthesisas well as an improved version of phase distortion.
* [http://patft.uspto.gov/netacgi/nph-Parser?patentnumber=4658691 Ishibashi; Masanori, Oct 17, 1985]
* [http://www.mcrow.net/White%20Crow.htm Virtual Phase Distortion Synth]
Wikimedia Foundation. 2010.
Look at other dictionaries:
Distortion synthesis — is a group of sound synthesis techniques which modify existing sounds to produce more complex sounds (or timbres), usually by using non linear circuits or mathematics. While some synthesis methods achieve sonic complexity by using many… … Wikipedia
Phase distortion — In signal processing, phase distortion or phase frequency distortion is distortion that occurs when (a) a filter s phase response is not linear over the frequency range of interest, that is, the phase shift introduced by a circuit or device is… … Wikipedia
Phase Distortion-Synthese — Die PD Synthese ist ein in den 80er Jahren von der Firma Casio erfundenes Verfahren zur Tonerzeugung bei Synthesizern. Das Verfahren arbeitete mit Samples von nur einer Periodendauer, die auf der damaligen Hardware preiswert speicherbar waren. Um … Deutsch Wikipedia
PD-Phase Distortion-Synthese — Die PD Synthese ist ein in den 80er Jahren von der Firma Casio erfundenes Verfahren zur Tonerzeugung bei Synthesizern. Das Verfahren arbeitete mit Samples von nur einer Periodendauer, die auf der damaligen Hardware preiswert speicherbar waren. Um … Deutsch Wikipedia
Distortion — This article is about technology, especially electrical engineering. For other uses, see Distortion (disambiguation). Distort redirects here. For other uses, see Distort (disambiguation). A distortion is the alteration of the original shape (or… … Wikipedia
Phase shift module — A phase shifter is a microwave network which provides a controllable phase shift of the RF signal [Microwave Solid State Circuit Design, 2nd Ed., by Inder Bahl and Prakash Bhartia, John Wiley Sons, 2003 (Chapter 12)] [RF MEMS Theory, Design and… … Wikipedia
Frequency modulation synthesis — In audio and music frequency modulation synthesis (or FM synthesis) is a form of audio synthesis where the timbre of a simple waveform is changed by frequency modulating it with a modulating frequency that is also in the audio range, resulting in … Wikipedia
Speech synthesis — Stephen Hawking is one of the most famous people using speech synthesis to communicate Speech synthesis is the artificial production of human speech. A computer system used for this purpose is called a speech synthesizer, and can be implemented… … Wikipedia
Digital waveguide synthesis — is the synthesis of audio using a digital waveguide. Digital waveguides are efficient computational models for physical media through which acoustic waves propagate. For this reason, digital waveguides constitute a major part of most modern… … Wikipedia
Sound synthesis — Basics of sound When any mechanical collision occurs, such as a fork being dropped, sound is produced. The energy from the collision is transferred through the air and other mediums, and if heard, into your ears. On a small scale, the collision… … Wikipedia