Guitar effects

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Guitar effects are electronic devices that modify the tone, pitch, or sound of an electric guitar. Effects can be housed in effects pedals, guitar amplifiers, guitar amplifier simulation software, and rackmount preamplifiers or processors. Electronic effects and signal processing form an important part of the electric guitar tone used in many genres, such as rock, pop, blues, and metal.

Guitar effects are also used with other instruments in rock, pop, blues, and metal, such as electronic keyboards or electric bass.

The TS9 Tubescreamer from Ibanez, a popular pedal adding vacuum tube-like distortion (via transistors) to the output signal from electric instruments.
The TS9 Tubescreamer from Ibanez, a popular pedal adding vacuum tube-like distortion (via transistors) to the output signal from electric instruments.

Contents

[edit] Distortion-related effects

[edit] Distortion

Distortion is an important part of an electric guitar's sound in many genres, particularly for rock, hard rock, and metal. A distortion pedal takes a normal electric guitar signal and distorts the signal's waveform by "clipping" the signal. There are several different types of distortion effects, each with distinct sonic characteristics. These include regular distortion, overdrive (or vacuum tube-style distortion), and "fuzz".

Although most distortion devices use solid-state circuitry, some "tube distortion" pedals are designed with preamplifier vacuum tubes. In some cases, tube distortion pedals use power tubes or a preamp tube used as a power tube driving a built-in "dummy load." Distortion pedals designed specifically for bass guitar are also available. Some distortion pedals include:

[edit] Overdrive

Some distortion effects provide an "overdrive" effect. Either by using a vacuum tube, or by using simulated tube modelling techniques, the top of the wave form is compressed, thus giving a smoother distorted signal than regular distortion effects. When an overdrive effect is used at a high setting, the sound's waveform can become clipped, which imparts a gritty or "dirty" tone, which sounds like a tube amplifier "driven" to its limit. Some overdrive pedals include:

[edit] Fuzz

Fuzz is intended to recreate the classic 1960's tone of an overdriven tube amp combined with torn speaker cones (such as You Really Got Me by The Kinks). Some fuzzbox pedals include:

[edit] Power-tube pedal

A Power-Tube pedal contains a power tube and optional dummy load, or a preamp tube used as a power tube. This allows the device to produce power-tube distortion independently of volume, so that power-tube distortion can be used as an effects module in an effects chain. Some examples are:

  • Hughes & Ketner Crunch Master
  • Stephenson Stage Hog
  • Damage Control Demonizer

[edit] Power attenuator

A Power Attenuator enables obtaining power-tube distortion independently of listening volume. A power attenuator is a dummy load placed between the guitar amplifier's power tubes and the guitar speaker, or a power-supply based circuit to reduce the plate voltage on the power tubes. Examples of power attenuators are:

  • Rockman Power Soak
  • THD Hot Plate
  • Marshall Power Brake
  • London Power Power Scaling circuit
  • Dr. Z Air Brake

[edit] Equalization-related effects

[edit] Equalizer

An Equalizer adjusts the frequency response in a number of different frequency bands. A graphic equalizer (or "graphic EQ") provides slider controls for a number of frequency region. Each of these bands has a fixed width (Q) and a fixed center-frequency, and as such, the slider changes only the level of the frequency band. The tone controls on guitars, guitar amps, and most pedals are similarly fixed-Q and fixed-frequency, but unlike a graphic EQ, rotary controls are used rather than sliders.

Most parametric EQ pedals (such as the [1] Boss PQ-4) provide semi-parametric EQ. That is, in addition to level control, each band provides either a center frequency or Q width control. Parametric EQs have rotating controls rather than sliders.

Placement of EQ in a distortion signal processing chain affects the basic guitar amp tone. Using a guitar's rotary tone control potentiometer is a form of pre-distortion EQ. Placing an EQ pedal before a distortion pedal or before a guitar amp's built-in preamp distortion provides preliminary control of the preamp distortion voicing.

For more complete control of preamp distortion voicing, an additional EQ pedal can be placed after a distortion pedal; or, equivalently, the guitar amp's tone controls, after the built-in preamp distortion, can be used. An EQ pedal in the amp's effects loop, or the amp's tone controls placed after preamp distortion, constitutes post-distortion EQ, which finishes shaping the preamp distortion and sets up the power-tube distortion voicing.

As an example of pre-distortion EQ, Eddie Van Halen places a 6-band MXR EQ pedal before the Marshall amplifier head (pre-distortion EQ). Slash places a Boss GE-7, a 7-band EQ pedal, before his Marshall amp. This technique is similar to placing a Wah pedal before the amp's preamp distortion and leaving the Wah pedal positioned part-way down, sometimes mentioned as "fixed wah," (pre-distortion EQ), along with adjusting the amp's tone controls (post-distortion EQ).

If a dummy load guitar-amp configuration is used, an additional EQ position becomes available, between the dummy load and the final amplifier that drives the guitar speaker. Van Halen used an additional EQ in this position. This configuration is commonly used with rackmount systems.

Finally, an EQ pedal such as a 10-band graphic EQ pedal can be placed in the Insert jack of a mixer to replace the mixer channel's EQ controls, providing graphical control over the miked guitar speaker signal.

Equalization-related effects pedals include Wah, Auto-Wah, and Phase Shifter. Most EQ pedals also have an overall Level control distinct from the frequency-specific controls, thus enabling an EQ pedal to act as a configurable level-boost pedal. Some EQ pedals include:

  • MXR 10-band EQ
  • Boss GE-7, PQ-4, EQ-20

[edit] Phase Shifter

A Phase Shifter creates a complex frequency response containing many regularly-spaced "notches" in an incoming signal by combining it with a copy of itself out of phase, and shifting the phase relationship cyclically. The phasing effect creates a "whooshing" sound that is reminiscent of the sound of a flying jet. Some electronic "rotating speaker simulators" are actually phase shifters. Phase shifters were popular in the 1970s, particularly used with electric piano and funk bass guitar. The number of stages in a phase shifter is the number of moving dips in the frequency response curve. From a sonic perspective, this effect is equalization-oriented. However, it may be derived through moderate time-based processing. Some phaser pedals include:

[edit] Wah-Wah pedal

A VOX wah-wah pedal.
Enlarge
A VOX wah-wah pedal.

A Wah-wah pedal is a foot-operated pedal, technically a kind of band-pass filter, which allows only a small portion of the incoming signal's frequencies to pass. Rocking the pedal back and forth alternately allows lower and higher frequencies to pass through, the effect being similar to a person saying "wah". The wah-wah pedal, used with guitar, is most associated with 1960s psychedelic rock and 1970s disco. During this period wah-wah pedals often incorporated a fuzzbox to process the sound before the wah-wah circuit, the combination producing a dramatic effect known as fuzz-wah. Some wah-wah pedals include:

[edit] Auto-Wah/Envelope Filter

An Auto-Wah is a Wah-wah pedal without a rocker pedal, controlled instead by the dynamic envelope of the signal. An auto-wah, also called more technically an envelope filter, uses the level of the guitar signal to control the wah filter position, so that as a note is played, it automatically starts with the sound of a wah-wah pedal pulled back, and then quickly changes to the sound of a wah-wah pedal pushed forward, or the reverse movement depending on the settings. Controls include wah-wah pedal direction and input level sensitivity. This is an EQ-related effect and can be placed before preamp distortion or before power-tube distortion with natural sounding results. Auto-Wah pedals include:

[edit] Vibe/Rotary speaker simulator

A Vibe or rotary speaker simulator pedal reproduces the sound of a rotating speaker. This is accomplished by synchronizing volume oscillation, frequency-specific volume oscillation, vibrato (pitch wavering), phase shifting, and chorusing in relation to a non-rotating speaker. The modulation speed can be ramped up or down, with separate speeds for the bass and treble frequencies, to simulate the sound of a rotating bass speaker and a rotating horn. This effect is simultaneously a volume-oriented effect, an equalization-oriented effect, and a time-based effect. Some vibe pedals also include an overdrive effect, which allows the performer to add "tube"-style distortion. Some Vibe pedals include:

[edit] Talk Box

Early forms of the talk box such as the Heil Talk Box used the guitar amplifier's output to drive a speaker horn that pushed air into a tube held in the player's mouth, which filters and thereby shapes the sound. Newer devices, such as Danelectro's Free Speech pedal, use a microphone and vocoder-like circuit to modulate the frequency response of the guitar signal.

[edit] Volume-related effects

[edit] Volume pedal

A Volume pedal is a volume potentiometer that is tilted forward or back by foot. A volume pedal enables a musician to adjust the volume of their instrument while they are performing. Volume pedals can also be used to make the guitar's notes or chords fade in and out. This allows the percussive plucking of the strings to be softened or eliminated entirely, imparting a human-vocal sound. Volume pedals are also widely used with pedal steel guitars in country music. Some volume pedals are:

[edit] Auto-Volume/Envelope Volume

Just as an Auto-Wah is a version of a Wah pedal controlled by the signal's dynamic envelope, there is an envelope-controlled version of a volume pedal. This is generally used to mimic automatically the sound of picking a note while the guitar's volume knob is turned down, then smoothly turning the knob up, for a violin-like muted attack. An example is:

  • Boss SG-1 (Slow Gear)

[edit] Tremolo

Tremolo is a regular and repetitive variation in gain for the duration of a single note, which works like an auto-volume knob. This is a volume-related effects pedal. This effect is based on one of the earliest effects that were built into guitar amplifiers.

[edit] Compressor

A compressor acts as an automatic volume control, progressively decreasing the output level as the incoming signal gets louder, and vice versa. It preserves the note's attack rather than silencing it as with an Envelope Volume pedal. This adjustment of the volume for the attack and tail of a note evens out the overall volume of an instrument. Compressors can also change the behaviour of other effects, especially distortion. When applied to instruments with a normally short attack, such as drums or harpsichord, compression can drastically change the resulting sound. Some compressor pedals are:

[edit] Time-based effects

[edit] Delay/Echo

A Delay or Echo pedal creates a copy of an incoming sound and slightly time-delays it, creating either a "slap" (single repetition) or an echo (multiple repetitions) effect. Delay pedals may use either analog or digital technology. Analog delays often are less flexible and not as "perfect" sounding as digital delays, but some guitarists argue that analog effects produce "warmer" tones. Early delay devices actually used magnetic tape to produce the time delay effect. Some common Delay pedals are:

[edit] Looping

Extremely long delay times form a looping pedal, which allows performers to record a phrase or passage and play along with it. This allows a solo performer to record an accompaniment or ostinato passage and then, with the looping pedal playing back this passage, perform solo improvisations over the accompaniment.

  • Boss RC-2
  • Z.Vex Lo-fi Loop Junky

[edit] Chorus

Chorus uses a cycling, variable delay time that is short so that individual repetitions are not heard. The result is a thick, "swirling" sound that suggests multiple instruments playing in unison (chorus) that are slightly out of tune. The chorus effect was popular in the 1980s. Some common Chorus pedals are:

[edit] Flanger

A Flanger simulates the sound effect originally created by momentarily slowing the tape during recording by holding something against the flange, or edge of the tape reel, and then allowing it to speed up again. This effect was used to simulate passing into "warp speed," in scifi films, and also in psychedelic rock music of the 1960s. Flanging is closely related to Chorus.

The first pedal-operated flanger designed for use as a guitar effect was designed by Jim Gamble of Tycobrahe Sound Company in Hermosa Beach, CA, during the early 1970s. No longer in production, the existing "Pedalflangers" appear occasionally on eBay and sell for several hundred dollars. A modern "clone" of the Tycobrahe Pedalflanger is sold by Chicago Iron.

[edit] Pitch-related effects

[edit] Octaver

An Octaver mixes the input signal with a synthesised signal whose musical tone is an octave lower or higher than the original. Effects that synthesize intervals besides octaves are referred to as harmonizers or pitch shifters, shown below. Octave Up pedals include:

  • Ampeg Scrambler
  • fOXX Tone Machine
  • Green Ringer
  • Tycobrahe Octavia

Octave Down pedals include:

[edit] Pitch Shifter

A pitch shifter is a device that alters the pitch of the instruments. They are generally used with an expression pedal to give a smooth bend-like effect. Pitch shifters can also be used to electronically "detune" the instrument. Some examples are:

[edit] Other effects

[edit] Feedbacker

Several approaches have been used to produce guitar feedback effects:

  • The neck pickup is used as a driver to push the strings based on the bridge pickup, such as in the Fernandes Sustainer guitars.
  • A pedal powers a headstock transducer, as in Sustainiac's Model C.
  • A handheld string driver can contain a pickup and driver, as in the EBow.
  • An effects pedal detects and sustains a note synthetically, as in the Boss DF-2 (Super Feedbacker & Distortion).
  • A dedicated high-gain guitar amp can be used in the control room, without a microphone, as a footswitch-controlled string feedback driver. The microphone is placed on the speaker cabinet of the main guitar amp in the isolation booth or live room.

[edit] Switcher/Mixer (or "A/B" pedal)

A switcher pedal (also called an "A/B" pedal) enables players to run two effects or two effects chains in parallel, or switch between two effects with a single press of the pedal.

Some switcher pedals also incorporate a simple mixer, which allows mixing the dry guitar signal to be mixed with an effected signal. This is useful to make overly processed effects more mild and natural sounding. Examples of the use of the mixer function include:

  • A wah can be mixed with dry guitar to make it more mild and full-bandwidth, with less volume swing.
  • A compressor can be mixed with dry guitar to preserve the natural attack of the dry signal as well as the sustain of the compressor.
  • Two overdrive pedals can be blended together.
  • A strong phaser effect can be mixed with dry guitar to make it more subtle and musical.

Some examples of switcher pedals include:

  • Dunlop A/B pedal

Some examples of Switcher/mixer pedals include:

[edit] Multi-Effects Pedals

A multi-FX pedal is a single effects device that contains a number of different effects in it. Some multi-FX pedals contain modelled versions of classic effects pedals or amplifiers. Some examples include:

[edit] Samples

Boss BD-2 (Blues Driver) modified to be a Fuzz.

Proco Rat distortion pedal modified by Indyguitarist.

[edit] Further reading

Wikimedia Commons has media related to:


[edit] See also

[edit] External links

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