An effects pedal, or stomp box, is an effects unit housed in a small metal chassis, used by musicians, usually electric guitar players as a guitar effects pedal, but sometimes players of other instruments including keyboards, violin, or cello. These devices alter the sound quality or timbre of the input signal, adding effects such as distortion, fuzz, overdrive, chorus, reverb, wah-wah, flanging, or phaser.

The TS9 Tubescreamer from Ibanez, a popular pedal adding vacuum tube-like distortion (via transistors) to the output signal from electric instruments.They are called pedals or stomp boxes because they sit on the floor and have large on/off switches on top that are activated by foot. Some, such as wah-wah or volume pedals, are also manipulated while in operation by moving a large foot-activated potentiometer.


Guitar effects pedals
A guitar effects pedal is connected into a signal chain using two 2-conductor instrument cables with 1/4" jack plugs (or "phone plugs"). The Input jack is usually on the right side, and Output on the left; thus the signal path for a chain of pedals is usually right-to-left. Some effects pedals have stereo out via two mono out signals, and a few have stereo input jacks as well as stereo output jacks. Several pedals can be linked together in a chain. An effects chain can be placed between the guitar and the guitar amplifier's preamp section, within the guitar amplifier's effects loop, after a guitar amplifier's Direct Inject line-level tap jack, after a dummy load attached to the guitar amplifier's output jack, or at the mixing board to process the miked guitar-speaker signal.

When a pedal is off or inactive, the signal coming in to the pedal is shunted onto a bypass, so that the "dry" or unaffected signal can go on to other effects down the chain, and thus any combination of effects on a chain can be created without having to reconnect boxes during a performance. True Bypass amounts to an isolated wire passing straight through the effects pedal, as opposed to buffered bypass, which can cause loss of treble, depending on the circuit.

The instrument signal can be routed through the stomp boxes in any combination, but to shape and preserve the clarity of the basic distortion tone, it is most common to put wah and overdrive pedals at the start of the chain; pedals which alter the pitch or color of the tone in the middle; and boxes which modify the resonance, such as flanging, delay (echo) and reverb units at the end. EQ, auto-wah, phaser, and vibe effects fit naturally at any position without introducing intermodulation distortion, while the emphatically time-based effects can sound unnatural and chaotic if placed early in the chain. Effects pedals can be used together with other effects units and a guitar amplifier's built-in

Guitar amp footpedals

Some guitar amplifiers have built-in effects such as Reverb and Tremolo and a switching pedal that turns the effects on or off. Channel switching between clean and distorted channels of a guitar amplifier's built-in preamp is also done with a switching pedal.

Pedals other than guitar effects pedals

Many other musical instruments, among them the piano, pipe organ, drums, and harp, also make use of pedals to achieve tonal, dynamic, or other effects. The piano's sustain pedal is one well-known example. Pipe organs have one or more expression pedals and sometimes a crescendo pedal, which the organist can use to achieve dynamic (or "expressive") changes. Strictly speaking, however, these are neither considered nor called effects pedals.


One major exception appears on modern electronic organs and synthesizers, which usually include a volume pedal similar to that of a guitar (indeed, the electronic organ and not the guitar pioneered this pedal), and some advanced models also include an additional effects pedal that may be programmed to serve several of the functions described in the preceding section.

Their operation of each is similar to those on guitars; the organist places an entire foot on the pedal and, while playing, gently pumps up and down with heel and toe pressure to achieve the desired effects. Because the organist is usually seated and thus has better balance than the guitarist, the pedals are designed to have a wider range of motion. The organist can thus bring about more pronounced changes than the guitarist with only slight changes in foot pressure, giving a greater level of control than the guitarist.

Some pedals also have switches on the end that enable still other effects by "scrunching" the toes to the left or right on the pedal, either in isolation or while pumping the pedal up and down, leading to far more flexibility than most guitar pedals.

See also

• Effects unit
• Guitar effects
• Guitar amplifier
• Distortion (guitar)
• Electric guitar

Originally published on Wikipedia