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Gain is defined as an increase (or reduction) in signal strength. Sometimes, gain-based guitar pedals do it with high fidelity regarding the input signal, meaning that guitar tone remains unaltered but boosted.

But most of the times (yeah) they add some juice to the tone, creating amazing textures for your light crunchy rhythms, thick power chords or the dirtiest leads.

You can think of the electrical signal coming out of the guitar as a pure sine wave. That is not really true, as the real signal does include tons of sine waves at different frequencies that adds up, which gives it its characteristic sound. However, it is a good and simple way you can visualize what occurs.

Now imagine you add some gain to this signal (you amplify it). You will have an exact copy of the input signal, but increased in amplitude (i.e. strength). You have a boost pedal here.

What happens if you add more gain? It will be a certain point (called threshold) where the signal will start clipping. The amplitude of the output sine wave can’t be higher, so it gets saturated. And what’s that? Yes, distortion. You have now an overdrive pedal.

How about adding even more gain? Well, the signal clips more, and the resulting output sine wave starts looking very different from a pure sine wave. The amplitude gets more saturated and you have more distortion. Here you have your distortion pedal.

Add more gain!! The output signal can get to a point where it gets so saturated that it can be seen as a square wave. Now you have something like a fuzz pedal

JRC-4558D Opamp
JRC-4558D Opamp

Why can the sound of pedal be so different from other from the same family? Why an Ibanez Tube Screamer TS-808 sounds differently from a Klon Centaur? Well, apart from the fact that the electronic circuits are different, the way that the clipped part of the waveform looks like is different in both cases.

You may have symmetrical clipping (i.e. the signal gets saturated identically at both high and low peaks) or asymmetrical clipping. You can also change the shape of the saturated region in many different forms.

Germanium clipping diode
Germanium clipping diode

The elements in charge of making the signal to clip in gain-based electronics circuits are Opamps (that include a few transistors) and diodes. Even with the same Opamp from different manufacturers you will notice a difference in the sound. Change the type of clipping diodes, and you will definitely notice how the sound changes… Check out this youtube video of a Klon Centaur clone with a few different clipping diodes. Which one did you like the most?

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:

  • Compressor pedals boost (or reduce) both the attack and decay of the signal, compressing it.
  • Boost pedals boost the signal, normally without distorting it.
  • Overdrive pedals add more gain and add some distortion, just like a cranked tube amp does naturally.
  • Distortion pedals add even more “natural” distortion, just like if you fully crank a stacked high-wattage tube amp.
  • Fuzz pedals add extreme distortion and amp-broken-like sound.

Compressor pedals

As their name indicates, compressor pedals compress the input signal, by smoothing the attack of the note and sustaining its decay, reducing the dynamic range of the input signal. 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.

Sometimes you won’t even notice the presence of a compressor pedal because you can’t hear any “artificial” boosting in the attack or in the decay of the sound, but you’d tell it’s there anyway. Stomp on the pedal, switch it off and you will miss its presence.

MXR vintage Dyna Comp
MXR vintage Dyna Comp

A little history…

Desktop compressor units have been present in all racks of any recording studio. With the appearance of solid state electronics, transistors substituted vacuum tubes, and smaller versions of compressors as stompboxes emerged.

First compressor stompboxes were very simple devices, designed around a basic Opamp IC with a few transistors, resistors and capacitors in there. However, compression circuits were a little more complex than other gain-based pedals, such as boosters and fuzzes.

Among the old pedals that started delighting guitarists with their compression effect in the sixties, you must credit the Ross Compressor, MXR Dyna Comp and Dan Armstrong Orange Squeezer. Today you can find modern (and vintage) reissues of old school pedals, or copies of them made by boutique brands.

Controls and features

You can find hundreds of compressor pedals. Most of them are very simple devices and include just one or two controls. However, you can also see more complex devices including a few more knobs that allow you to tweak the sound even further.

These are the typical features you may expect controlling with the knobs of a compressor pedal:

  • Attack. Adjusts the strength of the picking attack. Increasing its value (usually turning the knob clockwise) will result in a sharper attack, creating a more clearly defined sound.
  • Sustain. Adjusts the strength of the decay of the sound. Turn the knob clockwise and you will increase the sustain of your guitar.

Do I need a compressor pedal?

If you like the kind of compression that tube amplifiers apply to the sound, you may like tu use a compressor pedal to get a similar effect at lower volumes.

Compression comes very handy when playing in a band, so don’t hesitate to try one and bring it to your next rehearsal. You will notice the difference.

If you are into funk and/or soul music, you NEED a compressor pedal. There is no way you can get those funky guitars without one of those…

Boost pedals

Boost pedals simply increase the strength of the input signal. They are normally transparent, meaning that they boost the signal strength without distorting it.

They are great as a kind of High Fidelity 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.

However, some booster models can add a little distortion when turned all the way up. They can even fatten the sound adding more presence to your solo…

A little history…

In the mid sixties, when fuzz pedals were rocking on every stage, some guitarists started asking for some means of boosting the signal in order to drive the tube amplifiers harder at higher volumes, with no change in the sound (like fuzz did).

Electro Harmonix LPB1
Electro Harmonix LPB1

It was Electro Harmonix and its LPB1 booster, with its simple circuit based on a single transistor, the first one available on the market. It was a huge success, which contributed other brands to start producing similar stompboxes.

In the seventies, other pedals appeared too, such as the MXR Micro Amp and Dan Armstrong’s Red Ranger, contributing to the popularity of boosters among guitarists.

From there on, other brands started producing boosters. Today, there are are lots of boost pedals on the market. Some of them are very transparent, other tend to color the sound,  making it a little thicker or brighter, and other add a little distortion. Plenty of options for your particular taste…

Controls and features

Some models have controls for changing the tone of the sound (bass, treble, etc.), but you can expect boost pedals to be very simple stompboxes:

  • Boost. Boost, level, volume… you name it. The main knob of any boost pedal controls the level of the boost in the signal strength. Turn it clockwise, and the volume of your guitar will rise.

Do I need a boost pedal?

Well… I would say that a boost pedal fits in any pedalboard. If you are a jazz player, you may need some extra volume in your clean tone for soloing. On the other hand, you are looking for a warmer and crunchy tone in your overdrive or distortions. Add a boost pedal to your tube amp or overdrive pedal, and you’ll definitely find the difference.

In addition to that, it can result in a versatile and handy choice within large pedalboards, as the effect of boosting the signal also copes with signal (i.e. level and tone) loss due to long signal chains, similar to a buffer does.

Due to their simplicity, boost pedals are usually cheaper than other stompboxes (within the $100 price range) and fit any music style, so get one of those!

… By the way, the answer is yes, you DO need a boost pedal!

Overdrive pedals

Overdrive pedals are, by no means, the most popular of guitar pedals. They provide a higher gain than boosters, usually emulating the effect of a semi-cranked (or even fully-cranked) vintage tube amp.

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 to add a little crunchy bright tone, but you can get most of them by driving a cranked tube amplifier even harder. Just like tube amps like…

A little history…

Overdrive pedals were born to emulate the sound of a cranked tube amplifier. For this reason, they appear later than other gain-based pedals.

Ibanez TS808 vintage Tube Screamer
Ibanez TS808 vintage Tube Screamer

The godfather of overdrive pedals is, without any doubt, the Ibanez Tube Screamer TS-808. Most of overdrives you can find now in the market are either copies of the pedal or modified circuits based on the original model.

Other vintage overdrives have (and still are) very popular too, as the MXR distortion + or the Klon Centaur. This one uses a very different circuit and is considered the holy grial of overdrive pedals. It was discontinued long time ago and you will need $2.000+ in eBay to get one.

The mystery of this pedal is that the circuitry was covered with a black epoxy to prevent it to be copied. However, you can find a few models that claim being exact clones of the Klone made by both mainstream and boutique manufacturers.

You might think that vintage overdrives have not enough drive or add a little (but holy sweet) distortion. Actual overdrives can be very dirty and can be seen also as distortion pedals. You can even find models with more than one channel, including different levels of drive, which makes them very convenient when playing live.

Controls and features

As overdrive pedals are the most popular (by no means) guitar pedal, the are tons of brands and millions of different models. Some of them may be populated with lots of features and different channels, but any of them includes the following controls:

  • Volume. This knob sets the volume of the effect, as simple as that.
  • Drive. Here comes the juice of its sound. This knob controls the amount of gain applied to the signal, so that it starts clipping and gets a little distorted. Turn it all the way up and you will rock with the sound of an overdriven tube amplifier.
  • Tone. This knob changes the tone of the sound, usually equalizing mid frequencies. You can go from low-mid heavier sounds to a high-mid warmer bluesy character with this control.

Do I need an overdrive pedal?

YES. Lots of them. no doubt here.

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  to very extreme metal-like thick sounds.

Just like overdrives, distortion pedals are very popular among guitarists, and there is no reason at all for not having a couple of distortion pedals in your pedalboard.

A little history…

ProCo Rat
ProCo Rat

Like overdrive pedals, distortion stompboxes were created to emulate higher levels of distortion generated naturally by high wattage tube amplifiers.

The ProCo Rat can be considered the first distortion pedal, which took the level of distortion of vintage overdrives (like the Tube Screamer TS-808 and MXR Distortion +) way up dirtier.

With the evolution of heavier sounds starting from the late seventies, some distortion pedals go beyond standard distortion sounds. Modifying the contour and reducing mids while increasing the bright of the tone, you will get into metal.

From classic rock to death metal, the variety of distortions you can generate with distortion pedals is infinite.

Controls and features

Distortion pedals contain very similar features and controls than overdrives, so you may expect to see similar controls here…

  • Volume. This knob sets the volume of the effect, as simple as that.
  • Distortion. Similarly to the drive knob of overdrive pedals, this knob controls the amount of gain applied to the signal, so that it clips and gets distorted. Turn it all the way up and you will rock with the sound of a (fully) cranked tube amplifier.
  • Tone. This knob changes the tone of the sound, usually equalizing mid frequencies. You can go from low-mid heavier sounds to a high-mid warmer bluesy character with this control.

Do I need a distortion pedal?

You may think that you don’t need a distortion pedal, because you are very happy with the distortion you get from your dirty channel of your tube amp.

Well, that might be ok, but you do love guitar pedals, don’t you? You can get many different distortion sounds with different pedals. You can even obtain the typical distortion of your favorite amplifier, so plenty of versatility here, get a few…

If you like distortion and you like rock or heavier sounds, add a few distortion pedals to your collection!

Fuzz pedals

A fuzzed tone can be way different from other classic distorted sounds. It gives a very thick compressed saturated sound with and endless sustain. Fuzz really changes the shape of the input signal, producing a sound that is similar to a broken amp.

Dunlop JDF2 Dallas Arbiter Fuzz Face
Dunlop JDF2 Dallas Arbiter Fuzz Face

Turn up the volume of a tube amplifier, and you will hear a sweet overdrive when it starts to break up. Turn it all the way up and you will have a distortion…

… Now remove one of the paired output tubes, bias the preamp tubes with the wrong values and make a hole in the cone of the loudspeaker with a screwdriver. Crank your amp all the way up. That is fuzz.

You have to notice though that you may find some fuzz pedals that are, in reality, distortion pedals. Fuzz is more than distortion, it goes a step further in the level of “dirtiness”…

A little history…

Fuzz pedals are “the godfather” of guitar pedals. It was the early sixties, and solid state electronics were taking over traditional vacuum tube-based circuits. Put one or two transistors with a few resistors and capacitors into a stompbox, and you got a fuzz.

Early fuzz models include Maestro Fuzz Tone, Sola Sound Tone Blender and Dallas-Arbiter Fuzz Face. Even though the last one came later, it can be considered as the one, pure myth. Why? Because of him: Jimmy Hendrix. Saint Jimmy Hendrix.

gty_jimi_hendrix_up_close_portrait_bw_thg_121120_wmain

This model has been widely cloned (in both circuitry and shape) and it is sold by many different brands. You can distinguish it not just by its tone, but also because of its smily face, fuzzy face.

They initially used in their circuits Germanium transistors, which made them poorly reliable. There was a huge dispersion between transistors, which made different exact pedals to sound different. It even happens today with fuzz faces.

Modern fuzzes use Silicon transistors, whose sound is considered to be harsher, to experiment with newer sound.

But the majority of manufacturers still dig on the old school Germanium transistors, not only to recreate vintage style fuzz tones, but to experiment with new kind of fuzzy sounds.

Controls and features

As previous gain-based pedals, you may expect to be able to control how the effect blends with the original sound (or any other means to vary the volume of the effect) and the amount of fuzz. These are the most common knobs included in the majority of fuzz pedals:

  • Volume. This knob sets the level (volume) of the effect, as simple as that. In some cases, you may find a blend knob, to control how the fuzzed sound mix with the original.
  • Fuzz. This knob controls the amount of gain applied to the signal. In this case, the signal doesn’t just clip, it get a squared-like shape instead. Turn it all the way up and you you will hear a broken (but sweet) amplifier.
  • Tone. This knob changes the tone of the sound, usually equalizing mid frequencies.

Do I need a fuzz pedal?

No, you don’t need a fuzz pedal.

But… you play guitar, and you like Jimmy Hendrix, don’t you? If you want to emulate his sound or just love dirty thick fuzzy sounds, try one and play the guitar intro of “Satisfaction” by Rolling Stones. Did you enjoy it? Buy it!

Here is the complete list of posts of this “pedals explained” series:

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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 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 to 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 guitar tone remains unaltered but boosted. But most of the times (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 the 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
    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 and 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) characteristic 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 the 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 to sound like if more than one is playing. To do so, it takes the input signal, doubles it, and put the doubled signal slightly out of time and tune 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, where originally designed to emulate the effect of a rotary speaker, like a classic Leslie cabinet. Similarly 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
    MXR vintage phase 90

    frequency 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 than phasers, with a similar sweep and motion to its 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, what 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 how 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.

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

You can head to the 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 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 number of repetitions.

    Electro Harmonix Cathedral reverb
    Electro Harmonix Cathedral reverb
  • Digital delay. The evolution of digital circuits allowed generating more complex type of delays, by adding more functionality and increasing the delay time and 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 an atmospheric recurring 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 of the history of rock guitar.

You can head to the 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 into the next level. This pedal works in 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 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.

    Cry Baby classic wah
    Cry Baby classic wah
  • Auto-wah. Auto-wah is very similar to the classic wah. It is also based in 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 or you 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 blends with the filtered sound, which rises the versatility of this kind of devices to produce analog-like synthesized interstellar sounds.
  • Equalization (EQ). This effect is pretty straightforward. It consists on 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 include octavers 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 the 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 all 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…

    Digitech Whammy V
    Digitech Whammy V
  • 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 octaver, 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 note according to a preset harmony. You can work with mayor 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 pedal typologies described before, there are many other kind of pedals that cannot fit into any of them. They can create create sounds that have nothing to see with the sound of a guitar.

You can head to the 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.

    Electro Harmonix micro synth
    Electro Harmonix micro synth
  • Talk Box. This pedal is used to create kind of voicy 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 to appear to “speak”.
  • Expression. Some stompboxes my 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.

 Guitar pedals explained (Part 2): Gain guitar pedals

 

Here is the complete list of posts of this “pedals explained” series: