AllpassN: table of contents

Filter: Schroeder allpass delay line with no interpolation.

Source: Delays.sc

A Schroeder allpass filter is given by the difference equations

s(t) = x(t) + k * s(t - D) y(t) = -k * s(t) + s(t - D)

where `x(t)`

is the input signal, `y(t)`

is the output signal, `D`

is the delay time, and `k`

is the allpass coefficient.

In this UGen, `k`

is computed as `k == 0.001 ** (delay / decay.abs) * decay.sign`

(0.001 is -60 dBFS).

This UGen quantizes the delay time to the nearest sample period, and will produce aliasing artifacts if the delay time is modulated. If these are undesirable properties, the more CPU-expensive alternatives are AllpassL which uses linear interpolation, and AllpassC which uses cubic interpolation.

From superclass: CombN

From superclass: CombN

in |
The input signal. |

maxdelaytime |
The maximum delay time in seconds. Used to initialize the delay buffer size. |

delaytime |
Delay time in seconds. |

decaytime |
Time for the echoes to decay by 60 decibels. If this time is negative, then the feedback coefficient will be negative, thus emphasizing only odd harmonics at an octave lower. |

mul |
Output will be multiplied by this value. |

add |
This value will be added to the output. |

// Since the allpass delay has no audible effect as a resonator on // steady state sound ... { AllpassN.ar(WhiteNoise.ar(0.1), 0.01, XLine.kr(0.0001, 0.01, 20), 0.2) }.play; // ...these examples add the input to the effected sound and compare variants so that you can hear // the effect of the phase comb: ( { z = WhiteNoise.ar(0.2); z + AllpassN.ar(z, 0.01, XLine.kr(0.0001, 0.01, 20), 0.2) }.play) ( { z = WhiteNoise.ar(0.2); z + AllpassL.ar(z, 0.01, XLine.kr(0.0001, 0.01, 20), 0.2) }.play) ( { z = WhiteNoise.ar(0.2); z + AllpassC.ar(z, 0.01, XLine.kr(0.0001, 0.01, 20), 0.2) }.play) // used as an echo - doesn't really sound different than Comb, // but it outputs the input signal immediately (inverted) and the echoes // are lower in amplitude. { AllpassN.ar(Decay.ar(Dust.ar(1,0.5), 0.2, WhiteNoise.ar), 0.2, 0.2, 3) }.play;

helpfile source: /usr/local/share/SuperCollider/HelpSource/Classes/AllpassN.schelp

link::Classes/AllpassN::

link::Classes/AllpassN::