WaveWarp 2.0 Component
      
Phasers:
Controllable 2-pole allpass
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Functional Description
Basic building block for constructing a controllable phaser effect.
The audio output is a filtered version of the audio input, employing
a time-varying 2-pole all-pass filter whose coefficients are dynamically
adjusted according to the control signal inputs.
IMPORTANT: In order to achieve a controllable phaser effect,
this component must be connected in parallel with the original signal,
thereby creating a time-varying notch filter. (On its own, it simply acts as a
time-varying all-pass filter and will not produce a phaser effect.)
The characteristics of the resulting notch filter depend on the
control inputs to the time-varying all-pass filter. The first control input
controls the instantaneous center-frequency (in Hz) of the notch; the second
control input controls the instantaneous bandwidth (in Hz) of the notch.
The depth of the notch is adjusted via the slider in the Parameter Window.
Maximum depth (lower limit of slider) implies a deep notch; minimum depth (upper limit
of slider) implies a shallow notch. The depth is fixed in time.
NOTE: A multi-stage (i.e. multi-notch) phaser
can be obtained by connecting multiple copies of this component in series,
then connecting this cascade in
parallel with the original signal.
(This works because a cascaded series of all-pass filters retains the
all-pass characteristics, which results in a set of notches when
connected in parallel with the original signal.)
Algorithm
This component is implemented
using a 2-pole IIR all-pass filter with time-varying coefficients.
See
[Zo]
for further information on 2-pole filters for audio applications.
When connected
in parallel with the original signal, the resulting notch filter
will have a time-varying center-frequency and bandwidth,
as required for creating the phaser effect.
See
[HRM]
for general information on audio effects.
Signal Implementations
| Audio signals | Control signals | Description |
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| Single input single output mono-mono | Double input | The first and second control inputs
determine the instantaneous center-frequency and bandwidth, respectively, of the notch filter (obtained when the component is connected in parallel with the original signal). The mono audio input is filtered and sent to the mono audio output. |
| Single input single output mono-stereo | Double input | The first and second control inputs
determine the instantaneous center-frequency and bandwidth, respectively, of the notch filter (obtained when the component is connected in parallel with the original signal). The mono audio input is filtered and sent (in duplicate) to the stereo audio output channels. |
| Single input single output stereo-mono | Double input | The first and second control inputs
determine the instantaneous center-frequency and bandwidth, respectively, of the notch filter (obtained when the component is connected in parallel with the original signal). Each audio input channel is filtered separately (but with the same filter coefficients). The filtered channels are then averaged and sent to the mono audio output. |
| Single input single output stereo-stereo | Double input | The first and second control inputs
determine the instantaneous center-frequency and bandwidth, respectively, of the notch filter (obtained when the component is connected in parallel with the original signal). Each audio input channel is filtered separately (but with the same filter coefficients) and sent to the separate stereo output channels. |
Related components:
Example DrawingBoards illustrating usage:
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