DigiTech RP21D manual Effect Types, Choruses and Flangers

RP21D User’s Guide Section Two - Editing Functions

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.

P I T C H

10 -5 cents 0 5 cents 10

1 sec	2 sec	3 sec
T I M	E	Modulated Sound
		Original Sound

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.

(DEPTH)AMPLITUDE FREQUENCY (SPEED)

SINE LFO

AMPLITUDE (DEPTH) FREQUENCY (SPEED) AMPLITUDE (DEPTH)

TRIANGLE LFO

FREQUENCY (SPEED)

SP1 LFO

(DEPTH)AMPLITUDE FREQUENCY (SPEED)

SP2 LFO

(DEPTH)AMPLITUDE FREQUENCY (SPEED)

SP3 LFO

(Modifiers only)

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

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