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KDFX Reference
KDFX Algorithm Specifications
Algorithms 156–160: Phasers
156 LFO Phaser
157 LFO Phaser Twin
158 Manual Phaser
159 Vibrato Phaser
160 SingleLFO Phaser
A variety of single notch/bandpass Phasers
PAUs: 1 each
A simple phaser is an algorithm which produces an vague swishing or phasey effect. When the phaser
signal is combined with the dry input signal or the phaser is fed back on itself, peaks and/or notches can
be produced in the Þlter response making the effect much more pronounced. Most of the phaser
algorithms presented here have built in low frequency oscillators (LFOs) to generate the motion of the
phasers. In the case of Manual Phaser, the phaser motion is left to you.
A phaser uses a special Þlter called an allpass Þlter to modify the phase response of a signalÕs spectrum
without changing the amplitude of the spectrum. Okay, that was a bit of a mouthful Ñ so what does it
mean? As the term Òallpass ÞlterÓ suggests, the Þlter by itself does not change the amplitude response of a
signal passing through it. An allpass Þlter does not cut or boost any frequencies. An allpass Þlter does
cause some frequencies to be delayed a little in time, and this small time shift is also known as a phase
change. The frequency where the phase change has its greatest effect is a parameter that you can control.
By modulating the frequency of the phaser, you get the swishy phaser sound. With a modulation rate of
around 6 Hz, an effect similar to vibrato may be obtained, but only in a limited range of Þlter frequencies.
By adding the phaser output to the dry input using, for example, a Wet/Dry parameter, you can produced
peaks and notches in the frequency response. At frequencies where the phaser is Òin phaseÓ with the dry
signal, the signal level doubles (or there is a 6 dB level increase approximately). At frequencies where the
phaser and dry signals are Òout of phaseÓ, the two signals cancel each other out and there is a notch in the
frequency response. You can get a complete notch when Wet/Dry is set to 50%. If subtraction is used
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