Most guitar effects pedals can be placed into these broad categories:
- Ambience Effects: add a noticeable delayed sound that is perceived as a second guitar part. Includes delay, echo, reverb, and sometimes chorus.
- Dynamics Processors: respond according to how lud you're playing. Common types include compression (which keeps increasing gain as your notes fade away to lengthen sustain), and noise gates (which shut off the sound while you aren't playing to reduce noise).
- Filters: modify your guitar's tone by altering its harmonics, phase, or freqiuency balance. Include wah-wah, phasers, flangers, chorus, treble boosters or other equalizers.
- Overdrive: creates a more electric-sounding tone (as opposed to an acoustic guitar sound), ranging from the warm sound of an overdriven amplifier to heavier distortion sounds.
- Pitch: changes the pitch of the note you're playing. These effects include pitch modified with a whammy bar on your guitar, through to electronic equivalents such as vibrato and benders, octave dividers and harmonisers.
- Volume: let you change your volume manually, like with a volume pedal; or automatically, like with the pulsating sounds of tremolo and Panners effects.
Common guitar effects include:
Chorus
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A true vintage chorus pedal works the same way as a flanger pedal. Chrous pedals mix a signal that varies constantly from less than 1 millisecond to a few milliseconds with the original input signal to produce a series of notches in the frequency spectrum. Chorus pedals use a longer delay than flanging, to create a sense of "spaciousness." The delay is usually on the verge of a perceived echo, although at some settings echo won't be noticeable. Longer delay settings have a distinct slap-echo sound. Chorus pedals apply little or no feedback, so their effect is more subtle. Variations of stereo chorus pedals provide a powerful "surround-sound" effect when the recording is played through a stereo system. The most common arrangement is to delay each channel separately so that as the delay is increased in one channel, it decreases in the other channel, and vice-versa. The delayed signals are mixed with the original input signal in each channel. Sometimes a small amount of a delayed "image width expansion" signal is applied in the opposite channel along with bass cut to reduce muddiness. Common controls are:
- Rate: controls how fast the frequency notches move.
- Depth: controls how far the frequency notches move.
- Pre-Delay: controls the delay time, which is modulated by rate and depth.
- Tone controls: control tonal balance of either the delayed signal alone, or the effect's output signal.
- Intensity (or Effect or Mix:): controls the level of the delayed signal, determining the magnitude of the depth of the frequency notches and the delay level.
- Mode: switchable among different delay configurations.
- LFO: changes the low-frequency oscillator waveform shape from sine, square or triangle; or modulates the LFO by another LFO for more random and unpredictable modulation.
Older chorus pedal circuits have BBD (bucket-brigade device) technology which prcoesses analog signals as charges representing your audio signal though a series of steps causing the delay. Many musicians felt that BBD technology's audio quality was poor, and treble response was limited. Digital signal processors are used in modern chorus pedals to provide a stronger chorus effect, but they sometimes adds a small out-of-tune effect that occurs when the pedal mixes the original input signal with one that is modulated slightly flat then sharp.
Compressors
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Compressors are commonly used in recording to restrict dynamic range (the difference between the levels of the loudest and quietest sounds) by making loud sounds quieter, and quiet sounds louder. Typically compressors allow a vocalist to sing quietly and loudly for different musical emphasis, yet always be heard clearly in the mix. Compressors for guitars are used to enhance a guitar's clean sustain, by increasing gain automatically as the note decays. Compressors react almost instantly to a picked note, so finding settings that react quickly enough to the volume change without killing the natural attack sound of your guitar is the difference between a good compressor and thos eof lesser quality. Think of acompressor as having the world's most perfect sound engineer adjusting your volume control while you play, turning volume down when you pick a note, then turning the volume back up slowly as the note decays. The level at which the compressor begins to change gain is called the "threshold." Compressors reduce gain of levels above the threshold smoothly and gradually. A limiter is similar to a compressor, but it has a very high gain ratio (changing gain rapidly and abruptly) so that all signals above the threshold never exceed the threshold. An expander reduces the gain of signals below the threshold. Expanders were once common in home stereos to increase the dynamic range of disc records and tapes, and were the decoder part of tape noise reduction systems like Dolby and DBX. They are rarely used with guitars because they reduce sustain and thin the sound of the guitar. A noise gate is a special version of an expander that immediately turns off any signals below the threshold; they're used for noise reduction purposes only.
Compressors have to increase their overall gain to make-up for the lowered maximum level that results from their operation. This characteristic boosts low level signals, which is perceived by the ear as longer sustain. Common stompbox compressor pedals implement this effect by increasing the gain boost as signal levels decrease. Compressor controls are:
- Sensitivity: sets the threshold level above which volume is reduced, and below which volume is increased.
- Attack: controls how quickly the compressor reacts to increasing signal level changes.
- Release: controls how slowly the unit reacts to decreasing signal level changes.
- Tone: compensates for perceived treble loss caused by the smoother volume dynamics. No treble cut is actually applied to the signal.
- Volume: (sometimes labeled Level or Makeup Gain): sets output level to match the average volume loudness when the compressor is bypassed.
- Mix: allows some uncomprossed signal to be combined with the compressed signal to add natural picking and fingering dynamics to the compressed sound.
Delay
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Delay pedals are an echo effect that replays the note you play one or more times after a delay period. The effect sounds like the echoes you might hear shouting into a canyon: "H E L L O... HELLO... hello ... hello...." Some delay systems actually used tape recorders that had a loop tape and multiple tape playback heads. The sound is recorded then replayed through one or more playback heads positioned farther along the loop, then ultimately erased, ready for the next recording cycle. Varying the mix from different playback heads and the speed of the tape creates a wide variety of delay effects, even causing rhythm patterns in the delays. Tape-based units suffer mechanical problems, broken tapes. Accurate head alignment was important and they are quite noisy. Modern delay pedals use digital signal processor technology. One stereo effect is ping-pong delay which repeats the sounds as if they are bouncing from left-to-right as they decay. Setting the Delay pedal with no feedback so that it creates a single delay having a brief Delay Time of 50 milliseconds or so at nearly the same Delay Level as the original input signal gives you the famous "doubling effect", because it sounds like two guitarists are playing the same thing in near-perfect unison. Increasing the delay to 100 milliseconds changes the effect to a slap-back echo. Common controls are:
- Delay Time: sets the interval between each repetition.
- Delay Level: sets the magnitude of each repetition.
- Feedback: sets how much delay is fed back to the input signal for the repetitions.
- Tone: cuts the treble response of the delayed signal so it does not distract too much from what you're playing and to recduce muddiness and excessive noise.
- Taps: mimics the multiple replay heads on tape based units, with options to position the taps anywhere between left and right output channels for interesting stereo effects.
Equalizers
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Equalizers are more intricate tone controls, designed to give more tone control than is possible with the basic amplifier bass, middle and treble controls. The two most common types of equalizer are the graphic and parametric. Graphic equalizers control the level at fixed frequency points, called bands. They provide a graphic representation of the overall frequency response created by the equalizer, therefore the name. The bands are logarithmic, with each frequency placed at a fixed multiple of the next lowest frequency to correspond to the way our ears perceive frequencies, including the notes in musical scales. A graphic equalizer's frequency ranges can be limited to suit particular instruments, such as bass or guitar, or it can cover the entire audible frequency range from 20 Hz to 20 kHz. More bands give you finer control, but require more adjustments to make broad frequency changes. The graphic equalizer is the easiest and most intuitive to use, but if you need to fine tune problem frequencies to reduce PA feedback, or to enhance acoustic guitars, a parametric equalizer is more useful. Parametric equalisers often have a bass and treble tone control that act as normal tone controls for broad tonal shaping; and one or more middle frequncy range controls. A parametric equalizer's controls are:
- Frequency: the frequency that is boosted or cut.
- Q (or Resonance or Bandwidth): alters the width of the band of frequhecies boosted or cut by the control. The higher the Q number the narrower the band of frequencies boosted or cut.
- Level: the amount of boost or cut.
Most equalizers have an output level control to allow you to compensate for any overall loudness changes made by the settings.
Flangers
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Flangers work similarly to phasers. Flangers mix a signal that varies constantly from less than 1 millisecond to a few milliseconds with the original input signal to produce a series of notches in the frequency spectrum. This short delay is too short for the extra signal to be perceived as an echo. A flanger produces a large number of notches that are spaced so that the peaks between the notches are harmonically related, creating a more natural and musical tone compared to phasers. You don't really hear the notches but what's left, which is a series of peaks. Flanging got its name from a techniaue used in recording studios. The same track was played on two reel-to-reel tape machines, and recording engineer gently touched the flange of one tape reel to produce a small delay between the machines. Then, then engineer touched the flange of the other reel, bringing the tape recorders back into synchronisation again, removing the delay. Common controls are:
- Rate: controls how fast the frequency notches move.
- Depth: controls how far the frequency notches move.
- Intensity (or Effect or Mix:): controls the level of the delayed signal, varying the depth of the frequency notches.
- Resonance: increases the magnitude of the effect by applying internal feedback that cuases repetitions of the signal. A low resonance setting creates an effect similar to the original studio tape recorder technique. A high resonance setting creates the "jet plane" effect.
Harmonizers
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Harmonizers add one or more notes to what you are already playing. Several variations of harmonizers exist, each providing very different sounds. Octave dividers add a distorted signal one or more octaves below the notes you're playing. They worked only on one single note at a time. Digital harmonizers use digital signal processor (DSP) circuits to analyze the signal and synthesize new notes in harmony with the original signal. The accuracy and quality depends on the ability of the circui to correctly analyze the pitch, duration and other characteristics of the note you're playing. Because of this lmitation, several harmonizers provide monophonic (single note) harmonies as an option with improved accuracy and/or quality. Monophonic mode works well vocals and solo instrument harmonies too. For guitar, polyphonic harmonies allow pitch shifting and 12-string guitar emulation on chords. You can set the harmonies to fixed intervals, such as up 5 semitones, or down 7 semitones. Some harmonizers have "intelligent" chord-based harmonies, so the interval is determined by they key you select and the note you play. You could select the harmonies to be a 3rd and 5th, in the key of C-major, and the harmonizer will change the intervals to always play in C-major. Advanced options allow you to select your own chord intervals or apply random pitch variations or corrections to add a human-player-like realism to vocal harmonies. Controls vary widely with the type and make of Harmonizer.
Limiter
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Limiters have a name that is almost self-explanatory: they limit the maximum volume that can occur. Limiters have no effect on signals below the threshold, instead they stop signals above threshold from increasing any further. Although limiters have an effect similar to a compressor reducing high signal levels, a limiter do not boost signals below threshold. They are commonly used in PA and sound reinforcement systems to prevent overloading the power amplifiers or speakers and in recording studios to prevent overloading the recording levels of ditigal recording equipment. Limiters may be useful in solid state guitar amplifiers to simulate a vacuum tube power amplifiers dynamics, but they really are not as good as "the real thing."
Common controls are:
- Threshold: sets the level above which levels are limited.
- Level: sets the master output level.
Noise Gate
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Noise gates reduce noise fropm other effects pedals or your guitar by electronically turning the volume down when you're not playing. Noise gates MUST be placed after the effect pedals that are producing excessive noise. A noise gate's circuit detects signal level then slowly fades down the volume while your playing level decays to prevent notes that are decaying naturally from being cut off too abruptly. All noise gates respond as quickly as possible to a new note after they have turned down, otherwise the next note's beginning would be muted. Very noisy effects can be hard for the noise gate to separate the signal from the noise. Common controls are:
- Threshold: sets the level below which volume is shut off.
- Decay: sets the time required to turn the volume off fully.
Overdrive & Distortion
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Overdrive and Distortion pedals mimic the sound of an overdriven amplifier that has been pushed well into clipping. A waide variety of these effect pedals are available today, tailored for different musical genres. The first were fuzz boxes that had a thin (bass-cut) buzzing tone. Later designs had a natural overdrive sound that is still popular, whether used for their overdrive tone, or as a relatively clean booster to push your guitar amplifier into overdrive. Smooth overdrive and distortion effects started with the fuzz-circuit designs of the 1960s. A wide variety of methods that distort a guitar signal are marketed under the generic description of "fuzz boxes." One of the most popular is the Fuzz Face used by Jimi Hendrix. A back-to-back diode pair is the heart of most fuzz circuits. Germanium diodes provide soft clipping and silicon diodes provide hard clipping. Overdrive effects use soft clipping, reducing signal gain beyond the clipping point. Distortion pedals create hard clipping, where signal level is increased well beyond the clipping point. Distortion is a harder sound, which is good for rock; overdrive has a more natural sound. Some pedals have asymmetrical clipping, where one side of the wave is clipped more than the other, which gives gives the final output signal waveform a slightly different sound. Usual pedal controls are:
- Gain: controls the amount of overdrive.
- Drive: controls the amount of overdrive.
- Tone: reduces excessive high frequency content caused by the actual clipping process to give a smoother, fuller sound.
- :Volume (or Level): balances the effect's signal level with the bypassed level, or to boost the signal for those "shredding solos."
- Bass, Middle, Treble: additonal tone controls.
Note that some companies label their controls with terms they think their customers will relate to, such as: Balls, Grunt, Guts, In-Yer-Face, Shred, or other descriptions.
Panners
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Panners, sometimes called round pan or circular pan, is a combination of two tremolo effects, one for the left channel and one for the right channels that are linked so that when volume increases in one channel it decreases in the other channel, and vice-versa. Panners effects "moves" the sound from one side to the other.
Common controls are:
- Speed: controls how fast the signal moves between channels.
- Depth: controls how much the signal moves between channels.
- Waveform: selects different waveforms to modulate the volume level, including sine, which gives a smooth effect; sawtooth, which gives a slightly less of a pulsating sound; square, which turns the sound on-and-off rapidly; and other random or combination waveforms.
Phasers
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Phasers aren't the famous weapon from Star Trek. They're a specially modified notch filter controlled by a built-in low frequency oscillator that automatically sweeps the notch filter up and down the frequency spectrum, causing phase changes that create the effect's sound. Phasers space the notches evenly across the frequency spectrum, forming an atonal, sometimes dissonant sound. You don't hear the notches because they are the frequencies that are removed from the signal. What you hear is the frequency peaks between these notches that result from the phase changes. Some phasers, especially early designs, did not apply any feedback to th esignal, creating a subtle effect that is ideal for textural rhythm playing. Phaser circuits mix the incoming signal from your guitar with a second signal that is phase-shifted across the frequency spectrum. The phase shift can be subtle or extreme, up toa theortical maximum of 0-degrees at 100Hz to a phase shift of 720-degrees at 5 kHz. When the signals are in phase (which occurs at 0-degrees, 360-degrees and 720-degrees) the signals add together and reinforce each other, providing no audible change. When the signals are out-of-phase (which occurs the most at 180-degrees and 540-degrees), they cancel each other completely, eliminating the frequencies. Constantly varying the frequencies where the phase cancellations occur gives the movement associated with phasers. Adding resonance enhances the frequency peaks whenever the signals are in-phase. Using resonance to enhance the central peak lets you get a sound similar to an automatic wah-wah. Each phase stage shifts the phase 180-degrees, so a 6-stage phaser gives a shift of 1080 degrees, with 3 out-of-phase frequency notches. Phasers having 4, 6, 8 and 10 stages are common, although each stage adds noise to the output signal. Noise gates are recommended following a phaser. A phaser with seveeral stages and a high resonance setting creats a sound similar to flanging, even though they are very different processes. The Univibe, made famous by Jimi Hendrix, was the first successful a phaser. Modern phaser circuits use matched FETs as thie rcontrol element, while the Univibe circuit used incandescent light bulbs and LDRs (light dependent resistors), giving them a more erratic, somewhat pulsating phaser sound.
A common phaser's controls are:
- Speed: controls how fast the notches move.
- Depth: controls how far the notches move.
- Resonance: controls how large or small are the frequency peaks.
- Mix: (sometimes called Intensity or Effect): control the depth of the notches.
Pitch Benders
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Pitch Benders emulate a guitar's tremolo (whammy bar). Controls allow setting how far and how fast pitch is bent, and how long it takes to return to normal. Pitch Benders are usually combined with vibrato and harmonizer effects processors. Controls vary widely with the specific make and model of pitch bender.
Reverb
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Reverb pedals mimic the sound you hear in rooms with hard walls, floor and ceilings (like your bathroom) that reflects sound bounces around the room after the initial sound ends. Reverb is comprised of a very large number of repeated sounds, with levels and tones that over time. Digital reverb pedals usually offer you a choice of different simulated environments, such as many sizes of rooms and halls, as well as studio-style effects, such as plate, chamber and reverse reverbs; or emulations of guitar amplifier spring reverbs. Reverse Reverb builds in intensity before cutting off abruptly. They were created by drummer Phil Collins for his legendary gated snare sounds. A reverb's controls are:
- Decay: sets how long it takes the reverb to fade to silence.
- Level: sets overall signal volume.
- Tone: alters frequency balance.
- Early Reflections: sets the strength and time constant of the repeated sounds that mimic reflections from nearby surfaces.
- Late Reflections: sets the strength and time constant of the repeated sounds that mimic reflections from distant surfaces.
- Volume Envelope: alters the reaction of the volume control to incomin signal level, creating a volume swell before decaying.
- Other controls may include Room Shape, Mode or Type with selections such as Hall, Plate, Cathedral, Stadium, Small Club and so forth.
Speaker Simulators
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Guitar speakers aren't like hi-fi or studio monitors designed for wide, flat frequency response and undistorted, highly-defined sound. Their unique distortions and colorations, along with their shaped frequency response, are an important part of the sound of your electric guitar. Speaker simulators, sometimes called speaker emulators, use electronic circuits to mimic the sound of a guitar speaker so you can record your guitar without having to use a microphone in front of a speaker. The quality of speaker simulators varies from remarkably good to truly awful soundig. All guitar simulators apply a generalized guitar speaker frequency response that rolls off lows gradually while highs are cut sharply above about 6 kHz. Good speaker simulators also emulate other cabinet frequency response characteristics, such as general low and midrange resonances as well as the detailed peaks and notches that occur above about 1 kHz. Common options are choice of cabinet type and speakers, closed or open back, microphone types and placement, and a mix of direct signal with the simulate dsignal. Digital emulators offer choices between specific types of guitar cabinets and specific speaker models. Controls usually include:
- Input Level: to allow excessive high levels to be reduced to the input requirements of the speaker simulator.
- Output Level: sets maximum output volume to match the gain of the next piece of equipment in the signal chain.
- Ground Lift: to change how signal grounds are connected in case a ground loop needs to be broken.
Tremolo
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Tremolo modulates the guitar's volume, like rapidly turning the volume control up and down. Combined with reverb, tremolo creates the classic surf guitar sound. Be aware that Fender incorrectly label tremolo as Vibrato on their amplifiers. Common controls are:
- Speed: controls how fast the volume varies.
- Depth: controls how much the volume varies.
- Waveform: selects different waveforms to modulate the volume level, including sine, which gives a smooth effect; sawtooth, which gives a slightly less of a pulsating sound; square, which turns the sound on-and-off rapidly; and other random or combination waveforms.
Vibrato
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Vibrato varies pitch smoothly between slightly flat and slighlty sharp, similar to the fingerboard technique of string bending, or operating the guitar's whammy bar. Because you can't bend a string flat, the vibrato creates an effect you cannot do on the guitar directly by playing it. Nore that Fender amplifiers have an effect labeled vibrato which is actually properly called volume modulation or tremolo; it's not true vibrato, so don't confuse Fender's vibrato with othe rvibratos. Common controls are:
- Rate: sets how fast pitch changes.
- Depth: sets how far pitch changes.
- Delay: regulates how often the effect is triggered automatically, which determines how long it takes to reach the set depth.
Volume Pedal
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Volume Pedals control your volume through a foot pedal so you can play hands-free and not have to adjust your guitar's volume control. Some pedals allow you to set a minimum volume, so you can always be assured that some sound will come through it, even with your heel fully down. Determine whether you can leave the pedal unattended with it set at some specific volume, because some will return to maximum volume unless you're operating the pedal. If you always use the pedal after some other effect that uses electronic switching or in the effects loop of your amplifier), then you will need a medium impedance pedal (50 to 100 kilohms), but if you need to use the pedal connected directly to your guitar, then you will need to use a high impedance pedal (500 kilohms or greater). Sometimes a volue pedal is referred to as an expression pedal.
Wah-Wah
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Wah-Wah creates a resonant peak between 400 Hz and 2 kHz, then moves the peak up and down, creating the distinct "wah-wah" sound. The movement is controlled by rocking a foot pedal back-and-forth in time with the music. Sometimes certain specialty stomp-box effects move the peak up or down according to your playing intensity. Different pedals sound special because of how the resonance changes as the frequency moves. Usually the resonance increases as the resonant frequency lowers. Therefore, some wah-wah pedals have a resonance switch to select different frequency ranges. The original Vox and Cry-Baby wah-wah pedals are considered the benchmark of quality, and as such have been extensively copied by other manufacturers over the years. A typical wah-wah pedal circuit has an inductor-capacitor filter that creates the resonant peak, which is why manufacturers often advertise the quality of the inductor they use.
