Operation Manual

6.25 Flanger 91
This module is the same as the Dual Gate Sequencer but with song mode added. To read more
about song mode, please refer to the Multi Sequencer module documentation.
6.25 Flanger
The Flanger module implements the effect known as “flanging” which
colors the sound with a false pitch effect caused by the addition of a signal
of varying delay to the original signal. This module has two inputs and one
output. The first input is the audio signal to be flanged and the second input
is a modulation signal that varies the delay and affects the apparent pitch.
The output is the flanged signal.
The algorithm implemented in this module is shown in Figure 43. The
input signal is sent into a variable delay line. The output of this delay is
then mixed with the “dry” signal and re-injected into the delay line with a
feedback coefficient.
variable delay line+
mix
feedback
Output Signal
Input Signal
Figure 43: Flanger algorithm.
The effect of the Flanger module is to introduce rejection in the spectrum of the input signal at
frequencies located at odd harmonic intervals of a fundamental frequency as shown in Figure 44.
The location of the fundamental frequency f 0 and the spacing between the valleys and peaks of
the frequency response is determined by the length of the delay line (f 0 = 1/(2delay)), the longer
the delay, the lower is f 0 and the smaller the spacing between the harmonics while decreasing the
delay increases f 0 and hence the distance between the harmonics.
The amount of effect is determined by the ratio of “wet” and “dry” signal mixed together as
shown in Figure 45. As the amount of “wet” signal sent to the output is increased, the amount
of rejection increases. Finally, the shape of the frequency response of the Flanger module is also
influenced by the amount of “wet” signal re-injected into the feedback loop as shown in Figure 46.
Increasing the feedback enhances frequency components least affected by the delay line and located
at even harmonic intervals of the fundamental frequency. As the feedback is increased, these peaks
become sharper resulting in an apparent change in the pitch of the signal.