A Schroeder allpass filter is given by the difference equations
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.
The input signal.
The maximum delay time in seconds. Used to initialize the delay buffer size.
Delay time in seconds.
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.
Output will be multiplied by this value.
This value will be added to the output.