The Stomp Box

the S T O _M P
B-O-X
Get that sound!

In the series about rock music hardware, we take a look at the effect pedal or stomp box.
Technical and musical greetings from
Kurt Starlit
- aka CykelKurt

This series includes:
1. The electric Guitar 2. The Stomp Box 3. The Microphone 4. The Amplifier 5. The Speaker 6. Organ & Synth 7. Record & Music Production 8. Drums & Rhythm Boxes

Latest update: 2016.July.12

A huge problem for the guitarist of the 1960s was his guitar (according to himself) had a tiny sound. The piano/keyboard man played chords and polyphonic melody simultaneously, while the guitarist had to fight six impossible strings which often got out of tune.

The answer to a prayer was the stomp pedal, launched in the mid 60s. Today, it is available in countless variants, but in those days we were only beginning to see an electronic revolution...

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Distortion

Big Muff distortion from Electro Harmonix

Big Muff diagram

Big Muff demo

Big Muff schematics

It's 1965, when the distortion unit for the first time is heard. It's happening on The Rolling Stones song, "Satisfaction".

The distortion unit, or fuzz box, is a sonic revolution and many a guitarist don't sleep well at night, until he can finally lay his hands on this miraculous piece, called a stomp box.

For me personally, it happened on July 29, 1967 (a Saturday). It was the Schaller brand, a German gizmo (Verzerrer, as it read in German) which I had to pay 140DKK (12 pound or so) to get. Suddenly the world was wide open with this magic tool.

The Schaller Verzerrer on mother's fine carpet

A distortion unit or distortion pedal is, as the name implies, a pedal which distorts.

"She is distorting my intention," you could say, meaning, that she distorts or misrepresents the meaning of what you say. - Maybe she even distorts my intention beyond recognition.

In the same way, the distortion unit distorts the guitar's "natural" sound.

In practice, to generate distortion, you overdrive an amplifier input stage - a transisistor, a tube or a FET.

To "overdrive" means sending in a larger signal than the input stage can handle.

Different types of transistors distort differently (germanium, silicon, IC, FET, MOSFET, etc.). Walves (vacuum tubes) has their own specific way of distorting (generating second harmonics).

Therefore, there may be great differences in the type of distortion, the various transistors and walves generate.

Distortion / Fuzz

Any addition to the original sound (the original signal, the original keynote)
is regarded as Distortion.

No matter if the addition is wanted or unwanted,
harmonic or non-harmonic, the phenomenon is regarded distortion or fuzz.

Sending, for example, a pure clean tone (= a sine tone = a basic tone without harmonics)
to the input of a distortion unit or an amp,
on the output you'll find, apart from the original basic tone, a number of harmonics.

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Harmonics are tones,
whose frequency (pitch) is an integer multiple number of the basic note.
If, for example, 100 Hz is the basic note,
200, 300, 400, 500, 600, 700 Hz etc. are multiples integer of the basic note (frequency).

Listening tests have shown
that most people like harmonic overtones
- Especially the second harmonic (that's why tube amps are popular).

Similarly, it has been demonstrated
that most people do'nt like Un-harmonic overtones
(that's why early transistor amplifiers had an unpleasant sound).

As time went by, and the fuzz box became part of everyday life for most guitarists, the manufacturers began to work towards distortion pedals with so-called "soft fuzz". This means generating overtones which are related to the root frequency. The sound of a walve amp is the ideal, so this is why a generation of clumpsy walve distortion units are produced.

Soon, new and better semiconductors appears, which, in their way of working, remind of walves (e.g. FET and MOS FET transistors), it becme possible to make distortion pedals with soft fuzz and smart design.

If you take a look at available distortion units on the market today, it's obvious that there are many opinions on, how a distortion unit should sound (and look). The good thing about this variation is, that most guitarists nowadays can get their desires fulfilled. In those days we certainly couldn't do that.

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The Pedal
Taking the smash hit Zoom G1 pedal and adding a built-in expression pedal, this great processing unit offers an incredible array of features at one low price, in a unit that is so compact that it easily fits in your gig bag - even with an expression pedal built in!

Looking back at the time when the distortion box for the first time emerged in the mid-1960s, it seems like a gigantic development has happened on the guitar pedal front. Take, for example, at look at the Zoom G1X, which, despite its modest appereance, contains most of the pedal effects a guitarist needs.

Zoom G1X

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The Wah-Wah Pedal
is called so because it sounds so. In other words, it's a sound imitating name, just like a Crow is called a Crow because it says "crow".

Try for yourself, while simultaneously breathing in and out, to move cheeks and lips back and forth from a fully open position to a position of rounded lips. The wah effect should be easy to tell.

One famous wah pedal is Cry Baby from the Jim Dunlop company (by the way, they also make some fine pics).

When turning the wah pedal up and down, you are activating a filter or tone control, shutting up and down in accordance with the position of the pedal.

While simultaneously shutting up and down, the regulated frequency response of the filter is moving - see the diagram below.

An associated heavy resonance is likewise moving back and forth on the frequency response.

The result may sound like a wau-wau or wah-wah sound, as the guitar (or other instrument) is run through the filter.

In other words, the wah-wah effect could be explained as controlling a filter while simultaneously generating a sharp resonance. In short, this is called wah-wah.

Wah Wah pedal

The Technology of Wah Pedals

Dunlop Cry Baby (YouTube)

Woodoo Child (Jimi Hendrix)

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B-R-O-A-D sound
The Phaser, Flanger and Chorus pedals quickly became popular, as they emerged in the late 1960s and well into the 1970s. All three effects are closely related to each other, and came on the market as it was technically possible to manufacture electronic circuits (ICs) with the required time delay. Generally speaking, it is the length of the time delay, that represents the difference between them. The similarity is that they give the instrument (guitar) a rich or "wide" sound.

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The Vibratone
Before the phaser, flanger and chorus came on the market, Fender produced the so-called Vibratone speaker 1967-72. In many ways it was related to the Leslie speaker (see Hammond & Leslie on separate page).

Vibratone lifted the guitar into a sound universe of its own. But it came at with a heavy weight and at a price much higher than most guitarists were prepared to pay.

When the small electronic effect pedals came on the market, the Vibratone era was over, and it faded quietly out.

Vibratone test

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The Phaser
was the first electronic device of the three on the market, but was not substantially different to (electronic) flanger or chorus.

The phaser works like the signal (the guitar signal or "sound") on its way through the phaser pedal is divided into two. One part of the signal is led unchanged to the phaser output, while the other part of the signal is delayed within an electronic circuit - an IC (Integrated Circuit). How much it is delayed, is controlled by yet another circuit - a so-called LFO - Low Frequency Oscillator. As a result, the delay is constantly changing or wobbling. The LFO rate or frequency can be adjusted from the outside by means of a potmeter, located on the pedal surface.

At the output of the phaser pedal, the two signals are mixed together. The mixing ratio is controlled by means of one or more pots. In this way, you get the funky uzzy sound of a phaser, where certain frequencies (peaks) are hihighlighted, while others ar phased out (removed). These peaks and phase-outs are happening in accordance with the setting of various buttons on the pedal.

My my, as all this wasn't enough, they also got the idea of sending a small portion of the delayed signal back to the input - in technical litterature, this is called positive or negative feedback, depending on the feedback signal is in phase or out of phase with the original signal.

By adjusting the feedback (often controlled manually from the pedal under names like "notch", "peak", "depth" and "crunch"), you achieved that the "mountains" (peaks) and "valleys" (phase-outs) that were already there, were made even more clear and audible.

Phaser pedal sound could be compared to an old-fashioned AM radio: When listening to distant stations, they often disappear out in the blue, they "come and go". The phaser pedal effect is similar to this effect.

STEREO phasing / flanging / chorus
are in principle two mono pedals that work in parallel - side by side. The stereo sound is achieved by changing the delay slightly between the two (right and left) channels. This displacement is achieved in several ways, for example by phase shifting the control signal from the LFO to (just) one delay device. This creates a (continuously variable) temporal difference between the two channels, which means, that they are spatially experieced by the listener (guitarist).

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The Flanger
has got its name from the recording studios, which for many years had known the technique of letting two tape recorders play back the same piece of music (e.g. a guitar solo) through the same mixer. One tape recorder speed is varied manually a little bit by holding the thumb lightly against the tape spool edge - the flange.

In this way, one tape recorder speed wobbles, compared to the other. When the play back sound from two tape recorders are mixed, the resulting sound is the flanger effect.

Block diagram for an electronic flanger

When creating electronic flanging, the solution lies in the block called DELAY (see block diagram). This is where the delay and/or flanging of a (guitar) signal occurs.

You could even call flanging for "irregular time delay", because it is a delay of a (guitar) signal. But bear in mind: the delay shall be "wobbling" or irregular.

In order to produce this irregularity, the DELAY block is (voltage) controlled from a component which is also known from the analog synthesizer: VCO - Voltage Controlled Oscillator.

The control is obtained by applying a voltage to the control input of the DELAY block. This will cause it to change (time) delay of the (guitar) signal, transmitted through the block.

The irregularity is generated by an LFO (Low Frequency Oscillator), sending a very low frequency (e.g. 3 Hz) to the control input of the VCO. Let's assume that the LFO is already oscillating (generating) at 1,000 Hz per second. By mixing a 3 Hz low frequency with 1000 Hz, as a result you get a "swinging" tone from the VCO output, like e.g.

- gliding down to 900 Hz,
- gliding back to 1.000 Hz,
- gliding up to 1.100 Hz and
- gliding back to 1.000 Hz.

This gliding trip in the example is carried out 3 times per second.

It is this "wobble-tone" from the output of the VCO, that is applied to the control input of the DELAY block, where it affects the delay of the (guitar) signal irregularly - "wobbling".

On an electronic flanger, the time delay is within a range of 50-150 mS.

In this way we have generated the desired "wobbling" effect on the delayed (guitar) signal.

The only thing, which is still missing, before we can enjoy the spacey sound of electronic flanging, is to mix the two signals with each other. This is done up front of the flanger.

Example: Pictures of Matchstick Men (Status Quo, 1968), where it sounds like not only the guitar, but also other parts of the recording has been subjected to flanging.

John Lennon of The Beatles used the term "flanging" to refer to automatic double tracking, a technique developed at Abbey Road Studios by recording engineer Ken Townsend, in answer to producer George Martins joking assertion that the ADT effect employed a "double-bifurcated sploshing flange". This usage of the term is coincidental.

Flanging (or artificial double tracking as it was known at EMI) was first used on The Beatles song "Tomorrow Never Knows", written and sung by John Lennon in April 1966.

The first use of flanging effect in stereo is credited to producer Eddie Kramer who used the effect in the coda of Jimi Hendrix's song "Bold as Love" (1967). Kramer admitted in an 1990s interview that he read BBC Radiophonic Workshop technical journals for ideas and circuit diagrams.

Flanging

Electric Mistress diagram

Electric Mistress (demo)

Mistress Mystery

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Chorus
Chorus is in principle the same as flanging. The main difference is that chorus time delay is longer - some hundred milliseconds or more (if the delay becomes so long you can actually hear the "distance" between the direct signal and the delayed, it is called echo or delay). A guitar played through a chorus pedal sounds like several guitars playing the same (music) piece in unison or chorus - hence the name.

Chorus

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Echo
Echo is a repetition of sound - either once or a number of times (one time delay is sometimes called "delay"). The repetition arrives so late that it is audible delayed, compared to the direct sound.

The big shot in echo machines was Italian Binson, as it was use by all the professionals.

In many ways it reminds of a harddisk recorder (allthough it first emerged thirty years later). Unfortunately it was very expensive, so most mortal musicians had to settle for less.

Swissecho had a tape loop, running in an infinite loop. It worked quite well, but never reached the precision performed by Binson.

German company Schaller also produced a tape echo, which also worked guite well.

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Reverb
Reverb is in principle an infinite number of repetitions of sound - how long and how many can be adjusted.

In the 1960s, we only had the spring reverb, which is a long metal spring, through which you send the signal (from e.g. a guitar).

Before sending the signal through the spring, it is converted into a mechanical signal (by means of a transformer).

In this way, the electrical signal is converted into mechanical vibrations, and delayed during its way through the spring.

At the end of the spring, the mechanical signal (vibrations) is restored into an electrical signal, before finally mixed with the direct (original) signal from the instrument (the guitar).

The result is a sound which has been added to an infinite number of repetitions (echoes) - also known as reverb.

The spring reverb has got its limitations (e.g. it don't tolerate shaking). But also, it has got its charm, which is why so many contemporary guitarists still prefer the spring reverb.

After the valve reverb spring in the early 1950s, we had the transistorized in the 1960s. Then in the 1970s we had the analog reverb with the so-called BBDD circuits (Bucket Brigade Delay Device) built-in.

Much later came the digital reverb, which has almost infinite adjustability.

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Compressor / Sustainer
The Compressor and Sustainer are two pedals with opposite functions.

The compressor is doing its job by sending a small part of its output signal back to the input. Furthermore, the signal returned is in opposite phase of the input signal (= the two signals are of opposite phase). Take a look at Soul Preacher, IC 4558, bottom right..

This is called negative feedback.

Less negative feedback generates more gain.
More negative feedback generates less gain.

In other words: the gain in a Compressor pedal is controlled by the feedback.

At a low input signal, the compressor turns up the amplification.
At a high input signal, the compressor turns down the amplification.

The phenomenon is also called sustain, because the pedal in this way is trying to sustain the volume of the guitar.

EH Compressor / Sustainer

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Talking 'bout pedals...,
maybe we should take a look at New York based manufacturer, Electro-Harmonix, for example

"Zipper" (overdrive & envelope filter),

"Octave Multiplexer" (octave divider),

"Mini Q-Tron" (envelope filter),

"The Worm" (wah, phaser, tremolo, vibrato)

"Small Stone" (phaser),

"Memory Man" (echo, chorus, vibrato),

Holy Grail (reverb),

"Pulsar" (tremolo), and

"POG" (Polyphonic Octave Generator).

Some of these pedals are fantastic on stage, others work best in the studio - you'll have to try them to find out.

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A contemporary (2007) pedal: Roland Guitar Synth GR-20

Regarding tremolo and vibrato, maybe we should emphasize that tremolo means variation in volume, and vibrato means variation in pitch.

The whammy bar of a guitar therefore rightfully is called a vibrato arm, and not a tremolo arm, as it changes the pitch - not the volume. Electro-Harmonix "The Worm" is an example of a pedal that handles both tremolo and vibrato.

Rock n Roll Pedals

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This site is under constant consideration and expansion.
So, if you got an opinion on the topic in general or technical details in particular, don't hesitate to contact me:

Thank you very much!

Kurt Starlit
aka CykelKurt

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