NationMaster - Encyclopedia: Phase distortion synthesis

Phase distortion synthesis is a synthesis method introduced 1984 by Casio in its CZ range of synths, and similar to Frequency modulation synthesis in the sense that they are both build on phase modulation. Basically a sine wave is played, but by modifying the phase angle, the sine wave is bent out of shape. Image File history File links File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... 1984 (MCMLXXXIV) was a leap year starting on Sunday of the Gregorian calendar. ... Casio Computer Co. ... The Casio CZ-1000 synthesizer offered full sized keys. ... 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 a more complex waveform and a different-sounding tone. ... Phase modulation (PM) is a form of modulation which represents information as variations in the instantaneous phase of a carrier wave. ... In trigonometry, an ideal sine wave is a waveform whose graph is identical to the generalized sine function y = Asin[ω(x − α)] + C, where A is the amplitude, ω is the angular frequency (2π/P where P is the wavelength), α is the phase shift, and C is the...

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:

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. Image File history File links File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ...

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. The Hann window (sometimes called the Hanning window) is a mathematic function used in digital signal processing to avoid discontinuities at the two ends of a set of data. ...

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. In computer science, a lookup table is a data structure, usually an array or associative array, used to replace a runtime computation with a simpler lookup operation. ... The binary representation of decimal 149, with the MSB highlighted. ...

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. Image File history File links Download high resolution version (445x677, 7 KB)Figure 19 from the 1985 uspto Casio phase distortion synthesis patent application, depicting how to avoid sudden jumps in the variable resonance generation circuit. ... Image File history File links Download high resolution version (445x677, 7 KB)Figure 19 from the 1985 uspto Casio phase distortion synthesis patent application, depicting how to avoid sudden jumps in the variable resonance generation circuit. ... In acoustics and telecommunication, the harmonic of a wave is a component frequency of the signal that is an integer multiple of the fundamental frequency. ... In mathematics, a piecewise linear function , where V is a vector space and is a subset of a vector space, is any function with the property that can be decomposed into finitely many convex polytopes, such that f is equal to a linear function on each of these polytopes. ...

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 voltage-controlled filter (VCF) is a signal processing device in an analog synthesizer positioned after the oscillator. ...

Casio made five different synthesizers using this method of phase distortion synthesis. The Casio CZ-1000 synthesizer offered full sized keys. ...

The VZ-1's synthesis method ("Interactive phase distortion") includes Frequency modulation synthesis as well as an improved version of phase distortion. 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 a more complex waveform and a different-sounding tone. ...

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Simulating a resonant filter

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