Guitar Pedals Explained (Part 1): Introduction

There are literally thousands and thousands of different guitar pedals. They contribute to color the sound of the guitar, depending on the type of circuits they contain. You can listen to any kind of music record, and you will recognize the taste of guitar pedals.

From just a slight (and even imperceptible) signal compression up to a crazy fuzz, there is a great variety of guitar pedals. A common way to sort them is according to what they do with the signal that enters them, as listed here:

1. GAIN: boost, compression, overdrive, distortion, and fuzz.
2. MODULATION: chorus, phasing, flanging, tremolo, and vibrato.
3. ECHOING: analog delay, digital delay, and reverb.
4. FILTERING: Equalization and wah-wah.
5. PITCH SHIFTING: octaver, whammy, and harmonizer.
6. OTHER: Synth: talk-box, expression, and volume.

In the following sections, I will describe a little more these groups of effects, although I will write more in-depth, dedicated posts for each of them in this “pedals explained” series.

Gain Guitar Pedals

Gain is defined as an increase (or reduction) in signal strength. Sometimes they do it with high fidelity regarding the input signal, meaning that the guitar tone remains unaltered but boosted. But most of the time (yeah), they add some juice to the tone, creating amazing textures for your light, crunchy rhythms, thick power chords, or the dirtiest leads.

There are different types of gain-based pedals, depending on both the amount of gain and tone (due to signal shaping) they give to the guitar’s signal.

You can head to Part 2 of this series for a more in-depth description of gain-based guitar pedals.

• Compressor pedals. As their name indicates, these pedals compress the input signal by smoothing the attack of the note and sustaining its decay. This way, the sound of the guitar becomes a little thicker. In addition, there is less variation from note-to-note (and from note-to-chord) volume, which makes the sound more even and tight.
• Boost pedals. They are normally transparent, meaning that they boost the signal strength without distorting it. They are great as a kind of HiFi preamps, providing the signal with a level ready to rock when driving a tube amp. Sometimes they are used to simply increase the volume without coloring the sound of the guitar.Ibanez TS808 vintage tube screamer
• Overdrive pedals. They provide a higher gain than boosters, usually emulating the effect of a semi-cranked (or even fully-cranked) vintage tube amp. Overdrive pedals are, by no means, the most popular of guitar pedals. There is a huge variety of different models that give infinite flavors to the guitar tone, as they don’t simply increase the gain of the signal but introduce sweet different harmonic distortion into it. They are great to use with clean amplifiers, but you can get most of them by driving a cranked tube amplifier.
• Distortion pedals. Add more gain into the equation, and you will get more distortion. The range of distortion obtained with these pedals goes from the one you can get from a fully-cranked tube amp (or even less) to very extreme metal-like thick sounds.
• Fuzz pedals. A fuzzed tone can be way different from other classic distorted sounds. It gives a very thick, compressed saturated sound with endless sustain. Fuzz really changes the shape of the input signal, producing a sound that is similar to a broken amp.

Modulation Guitar Pedals

Modulation-based guitar pedals modulate one (or more) characteristics of the input signal, such as amplitude, frequency, or phase. From just slight phase shifting to orbital flanging, these pedals can definitely change the character of the sound of your guitar.

You can head to Part 3 of this series for a more in-depth description of modulation-based guitar pedals.

• Chorus pedals. The chorus effect tries to make one instrument sound as if more than one is playing. To do so, it takes the input signal, doubles it, puts the doubled signal slightly out of time, and tunes with the original. This way, when both the original sound and the doubled one are played at the same time, it seems like two instruments are playing together, but not in perfect tuning.
• Phaser pedals. Phasers, or phase shifters, were originally designed to emulate the effect of a rotary speaker, like a classic Leslie cabinet. Similar to chorus pedals, they split the input signal in two and modulate one of them in a less intuitive manner than a chorus pedal does. A phaser takes the doubled signal and shifts its phase between 0 and 360 degrees. This phase shift affects differently to each.
• MXR vintage phase 90
• Frequency is present in the original signal. When the shifted signal is mixed back with the original signal, some frequencies phase cancel while others add together to create notches and peaks in the frequency response. Modulating the filter’s phase shift with a Low-Frequency Oscillator (LFO) sweeps those notches and peaks up and down the frequency range over time to create a spacey whoosh and swirl effect.
• Flanger pedals. They are based on the same principle of modulation as phasers, with a similar sweep and motion to their sound. However, they usually apply more dramatic frequency-altering effects going on within that motion by imposing more control over the inverse points of the out-of-phase relationship, which results in a more oppressive effect. They are more complex devices, requiring more involved circuitry and, therefore, more control knobs than phasers.
• Tremolo pedals. By modulating the amplitude of the signal (i.e., volume level), you can obtain a helicopter-like pulsing effect at different speeds.
• Vibrato pedals. By slightly modifying the note above or below its original pitch, you obtain a warbling effect, similar to the one you obtain when bending a note of your guitar.

Delay and Reverb Guitar Pedals

Everybody knows what these effects are like. In fact, they try to reproduce the sonic effect that occurs naturally to any sound that propagates within a closed environment.

Whether you play in a bathroom, in a concert hall, or in a cathedral, you will experience how these types of environments affect the decay of the signal, as the (many) echoes bounce back from every direction (from walls, ceiling, floor) add up to the tail of the signal, expanding its decay.

You can head to Part 4 of this series for a more detailed description of time response-based guitar pedals.

• Analog delay. You experience echo in the natural world when you clap in the proximity of a hard, flat, somewhat distant wall and hear the sound come bouncing back to you at a delay determined by your distance from the surface. This effect generates echoes using analog circuitry, adding a little change in the tone of the repeats. Analog delay pedals are limited to relatively short delay times and a number of repetitions.
• Digital delay. The evolution of digital circuits allowed generating a more complex type of delay by adding more functionality and increasing the delay time and the maximum number of repetitions. Some pedals even include a built-in looping function that allows you to record short (or sometimes pretty long) riffs and repeat them infinitely, playing over the top.
• Reverb. Reverberation can be defined as the persistence of a sound after it has been produced. Reverb is commonly experienced in an empty, unfurnished room, or really in any chamber with walls, where multiple short echoes with long delays build up to a recurring atmospheric delay in the sound created in that room. It can be imperceptible in an open space or a crowded and fully carpeted chamber, and you can really notice its effect in a cathedral or a big cave.

EQ and Wah Guitar Pedals

These pedals modify the frequency spectrum of the signal. Apart from the basic filtering of the input signal via a graphic EQ, these pedals can produce awesome effects that you would instantly recognize as one of the most representative tones in the history of rock guitar.

You can head to Part 5 of this series for a detailed description of filtering-based guitar pedals.

• Wah-wah. This effect takes its name from the kind of sound that it generates. Another kind of classic pedal in the sixties rock scene, it also took disco music and funk in the seventies to the next level. This pedal works in a very simple way: by rocking the pedal with your foot, it controls an envelope filter, or band-pass filter, that creates a peak in the frequency spectrum. You increase or reduce the pass band of the filter by simply opening or closing the pedal with your foot. When that peak is swept through the portion of the spectrum in which the current note or chord is being played, it emphasizes those frequencies and produces a characteristic wah-wah-like sound.
• Auto-wah. Auto-wah is very similar to the classic wah. It is also based on an envelope filter circuit. However, you now don’t control the frequency characteristics of the filter with the foot; instead, this is done by the pedal automatically, depending on the dynamics of your playing and the settings of the pedal. This is a really cool funky effect that gives you a sound kind of different than a classic wah. If you are into soul and funk music, you definitely must have one of those.
• Envelope filtering. Auto-Wahs may be considered as a particular case of envelope filtering. The envelope filter pedals include different pass filter capabilities, as well as other knobs to generate sounds out of this world. Some pedals may even include low-frequency oscillators (LFO) that blend with the filtered sound, which raises the versatility of this kind of device to produce analog-like synthesized interstellar sounds.
• Equalization (EQ). This effect is pretty straightforward. It consists of a graphic EQ that includes a number of band pass filters at different frequencies. Depending on how many bands the EQ has, you really can change the tone of your playing. EQ pedals usually have slider-based controls to tune each band that present a graphic image of the shape of your EQ settings.

Pitch Shifting Pedals

Even though pitch-shifting pedals could be grouped with other filtering-related effects pedals, they generate such distinctive sounds and atmospheres that I have to include octaves and harmonizers in a separate category. What they basically do is generate additional notes (at different pitches) to the original, creating magical harmonies.

You can head to Part 6 of this series for a more in-depth description of pitch shifting-based guitar pedals.

• Octaver. An octave divider pedal splits the input signal and adds (or subtracts) an octave tone to the original. In some stompboxes, an octave can be added and subtracted at the same time and call them up to the original note. When adding an upper octave, you will get a trippy, psychedelic dual-part sound on single-note riffs, similar to the tome you can obtain with a 12 strings guitar. However, this effect may sound horrible when playing chords.
• Whammy. Take any recording of Rage Against the Machine, and you will hear Tom Morello creating very crazy tricks with it. This pedal works similarly to an octave, but now you can change the pitch of the note in different intervals, not just limited to octaves. In addition, you can modify the pitch while playing by rocking the pedal with your foot.
• Harmonizer. Harmonizers also work with the pitch of the input signal. In this case, they automatically process the tone of the note you are playing and add one (or more) shifted notes according to a preset harmony. You can work with major scales, minor, pentatonic, and so on. This can result in a relatively complex signal processing in order to get a natural and nice-sounding quality, so better go for a quality pedal here. If you like Brian May, you have to try out one of those.

Other Guitar Pedals

Apart from the effects of pedal typologies described before, there are many other kinds of pedals that cannot fit into any of them. They can create sounds that have nothing to see with the sound of a guitar.

You can head to Part 7 of this series for a more detailed description of other great guitar pedals.

• Synth. Synthesizer-like pedals create amazing sounds just like keyboard-like synthesizers. Instead of feeding the digital processors to synthesize sounds with a piano keyboard, you feed them with the strings of your guitar. And how do they work? They capture the pitch and volume of the notes (or chords) you are playing and generate a raw digital signal. Now you can do whatever you want with this signal: play a Hammond organ, a sitar… you name it.
• Talk Box. This pedal is used to create kind of voice effects. These pedals take the sound of the guitar and direct it to your mouth via a plastic tube with an adjacent microphone. Then you modify the sound by changing the shape of your mouth, “vocalizing” the sound of your guitar; this way, you make your guitar appear to “speak.”
• Expression. Some stompboxes have an additional input for an expression pedal, allowing you to control any of the pedal parameters (like effect level, speed, etc.) by rocking the expression pedal with your foot. It can be very handy as you may change some effects parameters while you play.
• Volume. A volume pedal may be seen as an amplitude modulating device. It allows you to control the volume of the guitar with your foot while playing. Usually placed at the beginning of the signal chain, it can change the way the rest of the subsequent pedals (and the amp itself) are driven. They are designed to be transparent, so the tone of the guitar remains unaltered; however, the way they react to your foot may be different among different pedals, as you may prefer either a linear or a logarithmic response when stomping on it.