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Probably the main thing to understand about effects is that
an effect modifies the sound it receives. Each has its own particular sound, although some
effects can sound similar to others.
Compact pedals, floor multi-effects & rack units
There are three main formats that effects appear in: Compact pedals, floor multi-effects
& rack mounted units
| Compact pedals Compact pedals are designed specifically for guitarists and are made to go in
between the guitar and the amplifier. They are small, and usually perform only one type of
effect, such as distortion or delay. They are designed to handle the low signal levels
that a guitar produces, and are not suitable for use in an amplifier's effect loop or with
line level signals. |
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| Rack mounted Rack mounted effects are larger and designed to bolt into the industry
standard 19" (48cm) rack cases. Originally they were designed for use in recording
studios and are often of a higher quality and more powerful than floor pedals. Rack
effects are frequently multi-effects - having more than one different type of effect in
the same box, and usually having more options and controls than pedal effects. |
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| Floor multi-effects As with compact pedals, floor multi-effects are designed specifically for
guitarists. They are usually much more powerful, and frequently include amplifier, speaker
and even microphone modelling as well as a whole array of guitar specific effects. One
major benefit of floor multi-effects is that they include foot pedals to switch sounds
with, as well as rocker pedals suitable for volume control and wah duties. |
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Multi-effects
It is increasingly common to find multi-effect units which contain any number of effects
in one convenient unit. As already mentioned, these can be in the form of a floor unit
with foot switches and rocker controls or rack mounted units with MIDI control which are
controlled via any MIDI capable footswitch.
The main attraction of multi-effect units is that effect
configurations and settings can be stored in convenient memory locations called patches.
When a patch is selected it recalls all the different effects used in the patch, the
effect order and all the individual settings used by each effect. This ability can save a
lot of the 'tap dancing' and knob tweaking which is necessary to control a number of
separate floor pedals.
Many multi-effect units also contain modelled amplifiers and
speaker simulators, often making them the only device needed for a gig - take your
multi-effect and guitar and plug straight into the PA and monitor system. If you prefer to
use just the effects and use a guitar amplifier and speakers onstage, just write your
patches with the amp and speaker simulations turned off.
Another advantage of multi-effect units is that they are cost
effective, costing many times less than all the individual effects together. However, it
is more of an initial outlay and you cannot buy one effect at a time as you can with
single pedals.
One disadvantage of multi-effect units is that it is a steep
learning curve for the beginner, to suddenly get a huge variety of effects in one go. The
way to get around this is to experiment with one effect at a time, learning how to use it
effectively before moving on to the next effect. There is also the possibility that you
will prefer a particular effect from another manufacturer, but most good Multi-effects
will allow you to insert a separate pedal into an effect loop, and then switch the loop -
and thus the effect - in and out as required.
Effect types
Effects fall into a number of broad-based categories, depending on how they achieve the
sound they create. These are:
- Distortion - which provide effects similar to
overdriven amplifiers
- EQ/Tone - which change the tone of the guitar
by changing the volume of different frequencies
- Modulation - which apply various pulsing
effects
- Time-based - which use time delayed sounds
- Pitch-based - which change the pitch of the
instrument
- Level/dynamics - which control the level of
the guitar or the dynamic range (the range of volumes from quietest to loudest)
The different effects and what each does
| Distortion effects |
Overdrive, distortion & fuzz
These effects are intended to produce the sound of
an overdriven valve amplifier, pushed well into its clipping region. This is the most
commonly used guitar effect of all.In
use
Overdrive is usually obtained with a technique called soft clipping, where gain is reduced
beyond the clipping point, giving a smoother, more natural sounding effect, with even
order harmonics (which are harmonically related to the note). Overdrive responds well to
dynamics - being less intense with softer playing and increasing in effect as the guitar
is played harder.
Distortion uses hard clipping, which makes for a harsher
sound with odd order harmonics. There is usually more gain than with overdrive.
Fuzz is the original distortion effect which is characterised
by extreme levels of drive and odd order harmonics.
Controls
Gain (often labelled as Drive) controls the amount of overdrive
Tone - compensates for additional highs created by the clipping process. There are
sometimes expanded tone controls, such as Bass, middle and treble.
Volume (or Level) - balances the effect volume with the bypassed level. It can also be
used to boost the signal for solos.
Guitar amplifiers & speakers
Guitar amplifiers and their speakers can be considered as distortion effects (and also as
tone modifiers!) Usage is basically the same as other distortion effects. |
| EQ/Tone effects |
Wah-wah
 The wah pedal produces
an effect like the vocal 'waa' sound which can be very expressive. In use
A wah creates its effect by a creating a 'peak' in the frequency spectrum (by boosting the
level of a narrow range of frequencies) and moving this peak up and down the frequency
spectrum.
Variations
There are three variations of wah effect; the pedal wah, the touch wah and the auto wah.
The pedal wah is controlled manually by moving a rocker pedal
similar to a volume pedal with your foot. A wah pedal can also be used as a distinctive
sounding 'tone control' if the rocker is left set at one position.
The 'touch wah' is an automatic wah. It moves the peak up or
down depending on the volume of the guitar signal. As you play a note, its natural volume
swell causes the peak to move up the spectrum and as the note dies out it moves back down
again.
The second automatic wah effect is the 'auto wah', which
moves the peak at a predetermined speed. This is actually a type of modulation effect, as
it uses a second waveform to modulate the signal.
Controls
The controls on a wah pedal are very basic: there is the rocker pedal and a bypass switch
to turn the effect on and off.
For an auto wah, there will be a rate control which controls
the speed that the peak is swept through the frequency range; a frequency control, which
sets where in the frequency range the effect operates; and a depth control, which sets how
wide a range of frequencies is covered.
The touch wah has similar controls to the auto wah but with a
sensitivity control instead of a rate, which sets how the effect responds to different
volumes.
Equalisers
 Sound Effect
Details
This effect is designed to give more tone control than is possible with the guitar or
amplifier controls.
In use
Graphic equalisers use sliders to control the level of specific fixed frequencies, called
bands. These provide a graphic representation of the overall frequency response.
Controls
Frequency sliders - one for each frequency to be modified.
Level control - allows you to compensate for any overall loudness changes made by the tone
changes. |
| Modulation effects |
Phaser
 Phasers have a
characteristic sweeping, 'whooshing' sound. The effect can be quite subtle if used on a
clean sound, but also create a more radical effect on a distorted sound.In use
This effect is created by moving notches (cuts in level across a narrow range of
frequencies - the opposite of a peak), up and down the frequency spectrum automatically at
a set rate.
Controls
Speed or rate - controls how fast the notches are moved
Depth - controls how far through the frequency spectrum the notches are moved
Resonance - controls the level of the frequency peaks
Chorus
 Chorus works the same
way as flanging and has a similar sound. However, it uses a longer delay than flanging, so
there is a perception of "spaciousness", which is particularly good for stereo.
There is also little or no feedback, so the effect is more subtle.
In use
Vibrato mixes a varying delayed signal with the original to produce a large number of
harmonically related notches in the frequency response.
Controls
Speed or rate - controls how fast the notches are moved
Depth - controls how far through the frequency spectrum the notches are moved
Pre-Delay - controls the delay time
Tone controls - are sometimes available
Intensity (or Effect or Mix) controls the level of the delayed signal, and consequently,
the depth of the frequency notches and level of the delay
Flanger
 Flangers mix a varying
delayed signal with the original sound to produce a series of notches in the frequency
response. This effect is similar to a phaser but with more resonance, which adds colour.
In use
The important difference between flanging and phasing is that a flanger produces a large
number of notches, and the peaks between those notches are harmonically (musically)
related. A phaser produces a small number of notches that are evenly spread across the
frequency spectrum. With high resonance, you get the "jet plane" effect.
Controls
Speed or rate - controls how fast the notches are moved
Depth - controls how far through the frequency spectrum the notches are moved
Resonance - controls the level of the frequency peaks
Tremolo
 This modulates the
guitar volume, like rapidly turning the volume control up and down.
In use
Different versions use different waveforms to modulate the volume level. Sine waves give a
smooth effect as the volume fades in and fades out again. Saw wave forms offer a less
pulsating sound, square waves turn the sound off and on very quickly. Some tremolo pedals
allow you to select the waveform to use for modulation.
Controls
Speed - controls how fast the volume varies
Depth - controls how much the volume varies
Waveform - chooses the waveform to use for modulation
Panning
Panning is a stereo effect which moves the signal from left to right in
stereo.
In use
It is basically two tremolo effects, one for each of the left and right channels. They are
linked so that when volume is high in one channel it is low in the other, and vice-versa.
Controls
Speed - controls how fast the sound moves from one side to the other
Depth - controls how far the sound moves from one side to the other
Waveform - chooses the waveform to use for modulation
Vibrato
Vibrato varies the pitch smoothly between slightly flat and sharp. similar to the
fingerboard technique of string bending, moving a tremolo or the effect gained with a
rotary speaker.
In use
Vibrato is obtained by modulating the pitch of a signal. Fender amps have an effect
labelled vibrato which is actually volume modulation, or tremolo.
Controls
Rate and Depth - how fast and how far pitch is changed
Delay - often the effect is triggered automatically, and this sets how long it takes to
reach the set depth |
| Time-based effects |
Delays
 Delay is an echo
effect, it repeats the original sound one or more times, adding more notes at later times
than the original - can be like having a second guitarist play along with the first. In use
Early delays were tape based, using a record head and multiple playback heads. Modern
delays are digital, where the sound is converted to ones and zeros and stored in memory so
that it can be copied and played back repeatedly at later times. The older tape units lost
treble the more repeats there were, while the modern units can reproduce a perfect copy
every time.
More sophisticated units offer multiple taps, with options to
position taps anywhere between left and right output channels for interesting stereo
effects.
One popular stereo effect is ping-pong delay - where the
repeat sounds as if it bounces from left to right as it fades out. Another is doubling -
where a single repeat at a short delay time (about 50mS) at nearly the same level as the
original sounds like two players playing the same thing in near-perfect unison. By
increasing the delay a little more (about 100ms) you get a slap-back echo effect. Very
short delay times (1-12mS) produce phase cancellation at fixed frequencies and effectively
change the tone.
Controls
Delay time - sets the amount of time between the original sound and the repeat
Delay level - sets the volume of the repeated sound
Feedback - sets the number of repeats
Reverb
 Reverb (or
reverberation) is the persistence of sound you hear in a room where sound bounces around
the room for a while after the initial sound stops. It is made up of a very large number
of repeats, with varying levels and tones over time.
In use
Guitar amps with built in reverb use a spring reverb, where at least one long spring is
connected to two transducers. The first transducer acts as a speaker - playing the sound,
which reverberates backwards and forwards through the spring. The second transducer picks
up the resulting sound and mixes it back with the original signal.
Digital reverbs usually offer you a choice of different sized
rooms and halls, studio effects such as plate, chamber and reverse reverbs, and sometimes
emulations of guitar spring reverbs.
Better delay units may feature early reflections which
simulate the stage situation where the reflection from the wall behind the player is heard
first ad a distinct short echo.
Controls
Decay time - sets how long it takes the reverb to die away to nothing
Predelay - sets the amount of time between the original sound and the first reflection
Level - controls the overall volume and tone of the reverb
Tone - Changes the tonal balance of the reflections
Early reflection delay - the amount of time before the early reflection is heard
Early reflection level - the volume of the early reflection |
| Pitch-based effects |
Octave dividers (Octavers)
 Octave dividers are
simple pitch shifters, which create a signal one or two octaves below the signal at the
input, then combine it with the original signal. In
use
They only work on one note at a time, becoming confused if they encounter more. The
octaved signal is a square wave, which is similar to a distorted sound.
Controls
Range - sets how many octaves below the original the generated signal is
Octave level - sets the level of the generated signal
Level - sets the level of the combined signal
Pitch shifters
 Add one or more voices
to the notes to what you are already playing, similar to an octave divider or harmoniser.
However with pitch shifters you set the harmony voices to fixed intervals, such as up
seven semitones, or down five semitones.
In use
This has it's uses such as pitch shifting an octave higher, which works for a modern
sounding 12-string emulation.
Controls
Shift amount - for each voice, sets the interval to shift the pitch.
Fine tune - set for each voice, allows you to detune a voice slightly to give a thicker
sounding mix
Voice level - set for each voice. Allows you to mix the harmonies with the original
signal, assigning each it's own level in the mix.
Level - controls the overall level
Harmonisers
Harmonisers add one or more voices to the notes to what you are already
playing, similar to an octave divider or pitch shifter, the difference is that a
harmoniser offers "intelligent" chord based harmonies. This allows you to play a
line in a specific key and have one or more guitars playing harmony with you - in key.
In use
Harmonisers use digital techniques that preserve the tone and timbre of your playing. This
means the harmony guitars sound a lot like the original guitar sound. They may even allow
you to set your own chord intervals, and apply random pitch variations or corrections to
add extra realism to harmonies.
The notes generated are determined by the key (which you
set), and the note you play. You could, for example, set harmonies to be a 3rd and a 5th,
in the key of C major, and the harmony intervals will change to make sure that the harmony
lines are always in the C major scale.
Controls
Key - which sets what key the harmony is in
Interval - set for each voice added. Sets which interval the voice will play in relation
to the original note
Fine tune - set for each voice, allows you to detune a voice slightly to give a thicker
sounding mix
Voice level - set for each voice. Allows you to mix the harmonies with the original
signal, assigning each it's own level in the mix.
Level - controls the overall level
Pitch Bend Pedals
This is a digital effect which is designed to emulate a whammy bar via a rocker pedal.
This is done by using a pitch shifter whose shifting amount is controlled by the rocker
pedal. The output will be the effected sound only.
In use
Often these effects are combined with other digital pitch based effects such as vibrato or
basic harmoniser options.
Controls
Bend range - sets how far and how fast pitch is bent
and how long it takes to return to normal. |
| Level / dynamics |
Noise Gates
 Noise gates are in
their simplest form, merely a switch which gets rid of the noise you hear during quieter
parts of a signal by muting (switching off) the sound. This effectively reduces the
perceived level of noise in the signal.In
use
Noise is usually masked (hidden) by the signal, as it is normally at a much lower level in
comparison. However, as the signal fades away in quieter sections of the music, the noise
can become noticeable and even quite annoying. A gate works by fading out the signal when
it falls below a certain level (the threshold), muting both the signal and the noise. The
fade prevents notes which fall below the threshold from being cut off dead, giving the
sound a natural decay.
There is often a separate trigger input and output. When a
signal is applied to the trigger input, the gate opens (lets the signal through). This is
particularly useful when used for guitar signals as you can use the pure direct guitar
sound to control the gating of your noisy effects.
Controls
Threshold - sets the level below which volume is faded out.
Attack - controls how fast the gate starts working. Usually for guitar use you want it as
fast as possible, and many guitar-specific units will not feature this control at all
Decay - sets how fast the gate fades the volume
Attenuation - sets how much the gate reduces the level
Limiter
This effect is similar to a compressor reducing high volumes, but a
limiter does not boost low level signals.
In use
They are used to tame peaks in a sound without otherwise affecting the dynamics. Not often
used in guitar setups.
Controls
Threshold/Sensitivity - sets the level above which volume is cut
Attack - controls how fast the unit responds to volume increases
Release - controls at what level the effect turns off. Is usually set a little lower than
the threshold
Volume (or level) - allows you to set a level to match the general loudness when the
effect is bypassed.
Compression
 Compressors are
commonly used to control the level of a guitar by making loud passages quieter and quiet
passages louder. This is useful in allowing the sound to be heard clearly in a mix.
However, it is rarely an 'obvious' effect to the untrained ear.
In use
Compression is generally applied to a guitar to give clean sustain. The louder part of a
note is cut in volume and then, as the note fades away the volume is gradually boosted.
Controls
Threshold/Sensitivity - sets the level above which volume is cut, and below which volume
is boosted.
Attack - controls how fast the unit responds to volume increases
Decay - controls how slowly the unit responds to decreasing volume
Tone - compensates for a perceived treble loss, which is actually caused by the smoother
volume dynamics
Volume (or level) - allows you to set a level to match the general loudness when the
effect is bypassed.
Volume pedal
Simple devices which allow you to control the level of the guitar signal with your feet.
In use
Some models allow you to set a volume range, so you can adjust it to be at backing rhythm
level when turned down and solo level when turned up. |
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