A chorus pedal is an audio effect that creates a rich, shimmering sound by duplicating and modulating the original guitar signal. Here’s a detailed explanation of how it works:
Signal Splitting and Modulation
The chorus effect begins by splitting the incoming guitar signal into two paths:
- The dry signal: This is the unaltered original sound that passes through unchanged.
- The wet signal: This is a copy of the original signal that undergoes processing.
The wet signal is then subjected to two key processes:
Delay
The copied signal is slightly delayed, typically by about 20-50 milliseconds
16. This short delay is crucial for creating the illusion of multiple instruments playing simultaneously.
Pitch Modulation
The delayed signal’s pitch is then modulated using a low-frequency oscillator (LFO)
16. This LFO causes the pitch to fluctuate slightly above and below the original pitch, simulating the natural variations that occur when multiple instruments play the same note.
Recombination and Output
After processing, the wet (delayed and modulated) signal is mixed back with the dry signal
16. This combination creates the characteristic chorus effect, where it sounds as if multiple guitars are playing the same part with slight variations in timing and pitch.
Key Components and Controls
Bucket Brigade Device (BBD)
Many analog chorus pedals use a BBD chip to create the delay
2. This chip passes the signal through a series of capacitors, creating a time delay.
Low-Frequency Oscillator (LFO)
The LFO is responsible for modulating the delay time, which in turn causes the pitch variations
23. It typically produces a triangle or sine wave.
Control Parameters
Most chorus pedals offer the following adjustable parameters:
- Rate: Controls the speed of the LFO, determining how quickly the pitch modulation occurs68.
- Depth: Adjusts the intensity of the pitch modulation68.
- Level/Mix: Balances the ratio of dry to wet signal in the output68.
The Resulting Effect
The chorus effect creates a sound that’s fuller, wider, and richer than the original signal
8. It simulates the subtle differences in pitch and timing that naturally occur when multiple instruments play together, even when trying to play in unison3. This effect can range from a subtle thickening of the tone to a more pronounced, shimmering sound reminiscent of a 12-string guitar or even a small ensemble playing together7.By manipulating the rate and depth controls, guitarists can achieve a wide range of sounds, from a gentle, underwater-like warble to a more intense, almost vibrato-like effect7. This versatility has made the chorus pedal a staple in many genres, particularly in the lush, atmospheric guitar tones of 1980s pop and rock music.
