Effects unit

An effects unit, effects processor, or effects pedal is an electronic device that alters the sound of a musical instrument or other audio source through audio signal processing. These tools help musicians create new and exciting sounds that go beyond what the instrument can produce on its own.

Common effects include distortion/overdrive, often used with electric guitar in electric blues and rock music; dynamic effects such as volume pedals and compressors, which affect loudness; filters such as wah-wah pedals and graphic equalizers; modulation effects like chorus, flangers and phasers; pitch effects such as pitch shifters; and time effects like reverb and delay, which create echoing sounds.

Most modern effects use solid-state electronics or digital signal processors. Some older effects, such as Leslie speakers and spring reverbs, use mechanical parts or vacuum tubes. Effects are often found as stompboxes, small boxes placed on the floor that are controlled with footswitches. They can also be built into guitar amplifiers, instruments like the Hammond B-3 organ, tabletop units for DJs, and rackmounts. They are also used as audio plug-ins in formats such as VST, AAX, and AU.

Musicians, audio engineers, and record producers use effects units during live shows or in studios, often with electric guitar, bass guitar, electronic keyboard, or electric piano. While effects are most common with electric or electronic instruments, they can enhance any audio source, including acoustic instruments, drums, and vocals.

Terminology

An effects unit has many names, such as an effect box, effects device, or simply an effect. If it is a pedal that you step on, it may be called a stomp box, stompbox, effects pedal, or pedal. The sound that goes into the unit without any changes is called dry, and the changed sound that comes out is called wet.

Musicians who use many pedals often put them on a guitar pedalboard to make setup faster and protect the pedals when moving around. When effects are placed inside a special case called a rack mounted road case, it is known as an effects rack or rig. This also helps musicians set up more quickly because all the effects are already connected inside the case.

Form factors

Effects units come in different sizes and shapes. Stompboxes are small, often operated by a musician's feet during performances. They usually have simple controls like switches and knobs to change the effect. Connecting several stompboxes creates an effects chain, allowing musicians to combine different sounds easily.

Rackmount effects units are larger and designed to fit into special equipment racks. They often include many types of effects and can be controlled remotely. Multi-effects devices combine many effects in one unit, either as a pedal or a rackmount system. Some instruments and amplifiers also have built-in effects, like reverb or distortion, though they may offer fewer adjustment options.

History

The earliest sound effects were used in recording studios. Engineers used special microphones and spaces to mimic the sound of different performance venues. In the 1940s, musicians like Les Paul began using tape to create echo and unusual sounds. The first stand-alone effects unit, the DeArmond Model 601 Tremolo Control, was released in 1941.

Effects built into guitar amplifiers were the first ones musicians used regularly outside the studio. Early amplifiers sometimes produced distortion when turned up too high, which guitarists began to use on purpose for a unique sound. The first popular portable effect was the 1958 Watkins Copicat tape echo, made famous by the band The Shadows.

The invention of the transistor allowed effects to be placed in small, portable boxes called stompboxes. The first of these was the 1962 Maestro Fuzz Tone pedal, used in the Rolling Stones’ song "(I Can't Get No) Satisfaction". As effects pedals became more common, they were used by famous guitarists like Jimi Hendrix and Pete Townshend. Even today, effects units continue to be important tools for musicians in creating new and exciting sounds.

Techniques

For broader coverage of this topic, see Sound effect § Techniques.

Distortion

Distortion adds a warm, gritty, or fuzzy character to sound by changing the shape of audio waves. It creates warm sounds by adding extra tones or gritty sounds by adding rough tones. Distortion is often used with electric guitars in rock and blues music.

Notable examples include the Boss DS-1 Distortion, Ibanez Tube Screamer, Marshall ShredMaster, MXR Distortion +, and Pro Co RAT.

A fuzz pedal creates a heavily distorted, fuzzy sound. Famous uses include The Rolling Stones' song "(I Can't Get No) Satisfaction".

Notable examples of fuzz effect units include the: Arbiter Fuzz Face, Electro-Harmonix Big Muff, Shin-ei Companion FY-2, Univox Super-Fuzz, Vox Tone Bender, Z.Vex Fuzz Factory.

Dynamics

Dynamics effects change the volume of an instrument. They were among the first effects used with guitars.

A boost or clean boost pedal makes the instrument louder, useful for solos. Volume pedals let players change volume with their foot while playing.

A compressor makes loud sounds quieter and quiet sounds louder, stabilizing volume.

Filter

Filter effects change which frequencies are louder or quieter in the sound.

An equalizer adjusts specific frequency ranges. Basic home stereos have simple equalizers, while professional graphic equalizers offer more control.

A wah-wah pedal creates vowel-like sounds by changing frequencies. It is often used in funk and rock music.

Modulation

Modulation effects change how the sound varies over time.

A chorus effect makes the sound thicker by adding slight variations. It is used in songs like "Come As You Are" by Nirvana.

A flanger creates whooshing or spaceship-like sounds. Famous uses include "Walking on the Moon" by The Police.

A phaser creates a rippling effect. It is used in songs like "Eruption" by Van Halen.

Pitch and frequency

A pitch shifter changes the pitch of the notes played. It can make notes sound higher or lower.

A harmonizer combines the original pitch with a shifted pitch to create harmonies.

Time-based

Time-based effects add echoes, reverb, or loops to the sound.

A delay/echo effect adds an echo to the original sound. It is used in songs like "Where the Streets Have No Name" by U2.

A looper pedal lets a performer record and replay phrases during a performance.

Reverb simulates the sound of a room or hall by adding echoes that fade away. It is used in rockabilly and surf guitar music.

Feedback and sustain

Audio feedback happens when amplified sound is picked up by a microphone and played back, creating a looping sound. In rock music, guitarists sometimes create feedback on purpose for special effects.

An Ebow makes a guitar note resonate continuously, creating a sound similar to a violin.

Other effects

Amplifier modeling replicates the sound of different guitar amplifiers.

Pitch correction effects adjust the pitch of a vocalist's performance.

Simulators let electric guitars mimic the sound of other instruments.

Bitcrushers reduce the quality of the sound to create special effects.

Rotary speakers create special audio effects by rotating speakers.

The Korg Kaoss Pad is a small controller and effects processor for audio and musical instruments.

Bass effects

Main article: Bass effects

Bass effects are special tools that change the sound of a low-pitched instrument like an electric bass or an upright bass. These effects can make the sound fuzzier or add a wavering effect, for example. Some bass amplifiers already have built-in effects like extra volume boost or a shimmering sound. Upright bassists in jazz, folk, and blues often use a small device called a bass preamplifier to help their sound travel better to the speakers. These preamps can also adjust the loudness and balance of different sounds.

Boutique pedals

Boutique pedals are made by smaller companies and often produced in limited numbers. Some are even handmade, with unique designs and high-quality parts. These pedals are usually sold online or in special music stores and can be more expensive than regular ones. Some boutique companies focus on recreating classic effects from the past.

Some well-known boutique pedal makers include: BJFE, Pete Cornish, Emlyn Crowther, Death By Audio, Robert Keeley, Roger Linn, Roger Mayer, Strymon, T-Rex Engineering, ToadWorks, and Z.Vex Effects. Some people enjoy modifying pedals to change how they work, adding new features or improving their sound. Popular pedals for modification include the Ibanez Tube Screamer, Boss DS-1, Pro Co RAT, and DigiTech Whammy.

Other pedals and rackmount units

Not all stompboxes and rackmounted electronic devices designed for musicians are effects. Strobe tuner and regular electronic tuner pedals help indicate whether a guitar string is too sharp or flat. These tuners route the guitar signal through a cable and usually have an output to plug into a guitar amp.

Rackmount power conditioner devices ensure equipment gets the right voltage to work properly. Wireless receiver units let guitarists or bassists move around on stage without cables. Switch pedals can turn built-in effects like reverb on and off in amplifiers. Some musicians use MIDI controller pedalboards or remote controls to trigger sound samples or change effect settings. A pedal keyboard is a foot-operated keyboard used to play basslines, not an effect unit.

Notable manufacturers

Many companies make effects units for musicians. Some well-known ones include Fender, Roland, and Ibanez. Others like Electro-Harmonix, Boss Corporation, and Line 6 also create popular effects pedals. These companies offer a wide range of tools to change and enhance the sound of musical instruments.