DigiTech RP21D - Manual (Page 33)

Effect Types
Pressing the Effects button will advance you to the next module in the Digital Effect chain. The procedure for editing each module will be
the same as the procedure previously described with the chorus. The only exception being that different effects will have different
parameters, and some may have a different number of pages. The following is a list of the types of effects available with the RP21D, and a
definition of the parameters.
Choruses and Flangers
Both choruses and flangers use a Low Frequency Oscillator (LFO) to produce their rich, swirling effects. When you change the speed and
depth Parameters of modulation effects, you're actually controlling the frequency and amplitude of the LFO. These settings determine the rate
and intensity of the modulation effect.
In general, here's how a chorus works: after entering the Module, the source signal is split into two paths. One is allowed to pass through
the Module unaltered, while the other is delayed and pitch modulated with an LFO. The modified sound is then sent to the output, along
with the original. In the following figure, a sine wave is used to modulate the pitch of the split sound source. The Dual Chorus creates two
different pitch “voices”, while the Octal Chorus creates eight voices for extremely full, rich sounds.
The only difference between choruses and flangers is that flangers use less delay and have a feedback Parameter that sends a portion of the
effected signal back to the input of the selected module. When the effected signal reaches the input, it is sent through the Module again,
building thickness and depth. If you increase the feedback enough, the source begins to lose its own original pitch to the dramatic pitch
modulation of the feedback loop.
LFO Waveforms : There are four LFO waveforms available for Choruses, Flangers, Phasers, Tremolos, Auto Panners. They include SINe,
TRIangle, SPecial-1, SPecial-2, and SPecial-3. The following examples show what these waveforms look like.
Chorus
Chorus is probably the most basic modulation effect. It is really just a very small delay whose time is always changing. As the time is varied,
the delayed signal's pitch changes (just like a tape recordings pitch raises when you play it faster). By moving the time back and forth, you
hear a sound that goes in and out of tune. When combined with the original sound, it almost sounds like more than one instrument is
playing. The RP21D uses several choruses at once to make huge rich sounds. For example, the octal chorus uses eight chorus voices at once
FREQUENCY (SPEED)
AMPLITUDE (DEPTH)
SINE LFO
FREQUENCY (SPEED)
AMPLITUDE (DEPTH)
TRIANGLE LFO
FREQUENCY (SPEED)
AMPLITUDE (DEPTH)
SP1 LFO
FREQUENCY (SPEED)
AMPLITUDE (DEPTH)
SP2 LFO
FREQUENCY (SPEED)
AMPLITUDE (DEPTH)
SP3 LFO
(Modifiers only)
PITCH
T I M E
-5 cents
0
5
cents
10
10
1 sec 2 sec 3 sec
Modulated Sound
Original Sound
28
RP21D User’s Guide Section Two - Editing Functions