Filtering pedals modify the frequency spectrum of the signal. You may know that any sound you generate is a combination of billions of sine waves, each at a given frequency, with a particular phase and with different amplitudes.

It is very straightforward to visualize the effect of filtering pedals if you think that they simply change the amplitude of some sine waves (at single frequencies) within a given frequency span.

But these pedals are much more than simple tone equalization devices, as they can apply filtering in the time domain, which provides cool dynamics to the tone and creates synthesizer-like effects.

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.

In this category, you will see amazing end epic effects, like the Wah-wah that Jimmy Hendrix (once again) made so popular in the sixties. But you’ll also see other awesome effects that use envelope filters.

  • Wah-wah pedals. I’m sure you know this effect. It takes its name for the kind of sound it generates. It is so great because you control it with your foot while playing.
  • Filter pedals. Known as envelope filters, these stompboxes are really cool. Auto-wah could be included in this category.
  • Auto-wah pedals. The effect it creates is very similar (even identical) to the one the conventional way pedal generates. However, you don’t control it with your foot, but it’s created automatically.
  • Equalizer pedals. These are really easy to understand. They allow you to equalize different frequency bands, very much like the tone controls of your amp, but with more versatility.

Wah-wah pedals

This effect takes its name from the kind of sound that it generates. It ¡s another example of the great classic pedals of the sixties rock scene; it also took disco music and funk in the seventies into the next level.

Wah-wah pedals work in very simple way: by rocking the pedal with your foot you sweep the center frequency of an envelope filter, or band-pass filter, through the frequency spectrum.

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 Wah
Cry Baby Wah

A little history…

Wah-wah sound has its origin back in the mid twenties, when trumpet and trombone players in the jazz scene produced such a sound when muting the instrument with their hand.

Regarding guitar world, it seems that the wah-wah pedal was invented by accident. It was mid sixties when VOX engineers were tweaking old tube amps, and they accidentally came up with an weird sound that everybody just loved.

They wanted to replace the expensive Jennings 3-position MRB circuit switch with a transistorized solid state MRB circuit. After adjusting the circuit, they connected its output to a speaker, and the sound surprised everybody around.

They used it with a saxophone, and after that they used a volume pedal to control the wah with a guitar. The rest is history…

VOS wah pedal was released in 1967. Once again, Jimmy Hendrix was the first to amaze the whole world with what this pedal could do with the sound of the guitar. From then on, Wah is considered to be essential in rock music.

The other mythical wah pedal is the CryBaby, which got its name due to the similarity of the tone that it generates with a baby crying. It came out in 1968, and I would say that it’s the most widely used wah-pedal .

In the seventies, funk, soul and disco music guitar players started massively using wah, which took this sound into the next level.

Controls and features

Wah pedals are very simple devices. You won’t usually see any knobs in them, although there are some models that allow you to change the bandwidth of the envelope filter. This way, if you select a narrow bandwidth you will get a sharper wah. On the contrary, if you increase the bandwidth the effect will be less noticeable.

Now, all wah pedals look the same, just like an actual pedal. By firmly stomping on it, you will activate the pedal so you can start rocking.

Do I need a Wah pedal?

It is a classic, and every guitarist should have one, so yes, you need a wah pedal.

Envelope filters pedals

Filters (envelope filters) are very similar to wahs and auto-wahs, although more versatile because they include more controls that allow you to amazingly shape the tone of your guitar.

Most of them include a low frequency oscillator (LFO) that is mixed with some of the controls that the filter has. In some cases, you can even modify the shape of the signal generated by this LFO (sine, square, triangle, etc.).

This is a wide category because there are very different filtering pedals, with very different functionalities and tonal possibilities. Some of them (really complex devices) provide, just with filtering, synthesizer-like sounds that will take your guitar out from conventionality.


A little history…

The history of envelope filtering is very related to the history of synthesizers.

Just check some recordings of the early progressive rock in the seventies and you will hear a lot of psychedelic synthesizer applying crazy filtering. Once again I will refer to Pink Floyd and “The dark side of the moon” and their mastery (though being just novices experimenting) with the use of synthesizers in the studio.

The first envelope filter was the Mu-Tron III, first made in 1972 and quickly becoming an essential effect for many funk musicians. Other examples of envelope filter pedals include the MXR Envelope Filter and the Boss AW-2 Auto Wah.

Envelope filter pedals are not really mainstream pedals. Although most mainstream brands have an envelope filter in their catalogue, there are not many models in the market (at least not as many as overdrives…)

This pedal also shaped the sound of funk.

Controls and features

In the case of (envelope) filter pedals, the controls vary widely among different stompboxes.

In any case, these are the most commons controls that you can find in the majority of filters:

  • Rate. With the rate you will control the time in which the frequency sweep occurs. Think about a wah pedal that you control with your foot: the faster you rock the pedal, the faster the wah sound is generated. You can obtain the same effect by increasing the rate of an auto-wah.
  • Depth. The depth knob changes the bandwidth of the envelope filter. At its minimum, you will get a subtle effect, whereas turned all the way up you will reduce the bandwidth, obtaining a sharper wah tone.
  • Sensitivity. Sometimes you can obtain a dynamic change in how the pedal reacts to your playing. If you play louder, the wah effect will be more pronounced. You will obtain more natural effect by tuning this control.
  • LFO. With this knob you can change the speed (frequency) of the LFO, from a slight vibe-like effect up to a high frequency helicopter-like high speed tremolo.
  • Envelope. Sometimes you can select between different shapes for the signal generated by the LFO (sine wave, triangular, square, etc.).
  • Mode. Some really cool pedals allow you to select between different modes of operation. Instead of having just a steady LFO with a constant output, they include a few presets with crazy oscillator patterns.

Do I need a filter pedal?

Not really. But trust me, they will boost your creativity, because they allow you to sound so amazing that you will get inspired by the effect itself.

I must admit that, when I’m writing these lines, I am waiting for a present that I’ve made to myself. A friend of mine is about to come from NYC, where he got for me a SolidGoldFx FUNKZILLA. What does this name suggests?

Do you like funk? Then you need a filter pedal.

Auto-wah pedals

Auto-wah is very similar to the classic wah, because 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.

Mad Professor Snow White AutoWah
Mad Professor Snow White AutoWah

A little history…

Auto-wah can be considered as a particular case of envelope filtering, so the history of envelope filters apply here.

Controls and features

Auto-wah pedals can be considered as a group within the envelope filters category. However, there are some models in the market with just auto-wha functionality.

in general, they will share these controls:

  • Rate. With the rate you will control the time in which the frequency sweep occurs. Think about a wah pedal that you control with your foot: the faster you rock the pedal, the faster the wah sound is generated. You can obtain the same effect by increasing the rate of an auto-wah.
  • Depth. The depth knob changes the bandwidth of the envelope filter. At its minimum, you will get a subtle effect, whereas turned all the way up you will reduce the bandwidth, obtaining a sharper wah tone.
  • Sensitivity. Sometimes you can obtain a dynamic change in how the pedal reacts to your playing. If you play louder, the wah effect will be more pronounced. You will obtain more natural effect by tuning this control.

Do I need an auto-Wah pedal?

Unless you are into funky stuff, you won’t be thinking in including an auto-wah in your pedalboard… But if you do like how synthesizers can color different sounds by adding filtering and LFOs you will love what these pedals can do with a guitar.

Equalization (EQ) pedals

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.

A little history…

MXR 10 band Equalizer
MXR 10 band Equalizer

Graphic equalizer pedals were widely used in the seventies. They’ve always been used to adequate the sound of the guitar when playing live at a particular venue.

The most popular EQ pedals were those offering 6 frequency bands. Everybody was offering EQ pedals, so you will find Electro Harmonix, Ibanez, DOD and other brands competing since these pedals first appeared.

Controls and features

Graphic equalizers are usually very simple devices to control. They usually have these controls:

  • Volume. You can boost (or attenuate) the output of your guitar with a volume control, after having equalized the sound.
  • Frequency band. You will be able to boost or attenuate different band frequencies independently, with the respective knob or fader. Faders are very convenient because they give you a graphic view of how the frequency equalization is shaped. In fact, they sometimes include an led so you can see the frequency shape on stage.

Do I need an EQ pedal?

You may think that this pedal is not for you, because you have enough EQ control with the knobs of your amplifier. Well, that is true if you are playing at home…

If you play live with a band, you will need some means of quickly equalize the sound coming out of your amp. The sonic characteristics of the venue may impose to boost some signal while attenuating others. You could even need to notch a given frequency to avoid an unwanted feedback to occur.

In addition to that, an EQ can make your guitar sound like it was produced in a recording. They will provide you with a lot of flexibility.

As I said before, if you play in a band in relatively big venues or you just want to be able to change drastically the tone of your guitar, put an EQ pedal on your pedalboard!

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


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.


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: