What Are Ring Modulation Effects Pedals & How Do They Work?


Ring modulation is one of the weirdest effects a guitarist could add to his or her pedalboard. The intriguingly odd sounds we can get out of a ring mod pedal have likely sparked your interest and inspired you to check out this article, where you’ll learn how they work.

What are ring modulation pedals and how do they work? Ring Modulation pedals are stompbox units designed for guitar and/or bass. They modulate the amplitude of the input signal with a carrier signal (typically a sine or square wave) in order to produce/output new frequencies which are the sum and difference (sidebands) of the input and carrier signals.

The resulting output signal from a ring modulator can be wildly different from the input signal. These pedals are quite experimental by nature and can be very exciting to use (and talk about).

In this article, we’ll further our understanding of ring modulation and the pedals that produce this strange effect. I’ll share a few pedal examples along the way and tips on how to get more out of your ring mod pedals.


Table Of Contents


What Is Ring Modulation?

Ring modulation is a type of amplitude modulation signal processing function. It utilizes a carrier wave and a modulator wave and produces multiple frequencies from these two signals. The frequencies produced are the sidebands (the sums and differences of the frequencies of the carrier and modulator signals).

To put it in a more straightforward fashion, ring modulation multiplies two input signals together to create two brand-new frequencies which are the sum and difference of the input frequencies.

Ring modulation utilizes two input signal: the modulator and the carrier. The modulator is nearly always the instrument input signal and the carrier is a signal produced by the ring modulator.

A device capable of ring modulation is referred to as a ring modulator. These electronic devices are most often seen with synthesizer units or modules. As the tile of this article suggests, they are also designed in the form of guitar pedals.

The label of “ring modulation” is derived from the analog circuit that produces the effect. This circuit utilizes several diodes in the shape of a ring, as is shown below:

This image has an empty alt attribute; its file name is mnm_Basic_Ring_Modulation_Circuit.jpeg
Simple Ring Modulator Circuit

The diodes in the circuit either face clockwise or counter-clockwise, depending on the schematic.

As we can see from the basic diagram above, we have an “input” modulator signal and another “carrier” input signal.

In the case of guitars (and other instruments), the modulator (labelled “input” in the picture above) signal will be the instrument signal and the carrier signal will be a waveform provided by the ring modulator. The carrier signal is typically a basic waveform (a sine, triangle, square, sawtooth or similar).

Basic Waveforms & Their Harmonic Content

As an aside, each basic waveform has its own harmonic characteristics. A harmonic is an integer multiple of the wave/signal/sound’s fundamental frequency (note value). These harmonic characteristics will help us to better understand ring modulation are can be summed up in the following:

4 Basic Waveforms
Sine (Green) – Square (Blue) – Triangle (Red) – Sawtooth (Orange)
  • Sine waves (green) have a single frequency (the fundamental).
  • Square waves (blue) have infinite odd-order harmonics (3x, 5x, 7x,.. the fundamental frequency) and each successive harmonic has less amplitude.
  • Triangle waves (red) also only have odd-order harmonics though the amplitude reduction of each successive harmonic is much greater.
  • Sawtooth waves (orange) have infinite even and odd-order harmonics (2x, 3x, 4x, 5x,.. the fundamental frequency) and each successive harmonic has less amplitude.

Once again, the carrier signal is produced by the ring modulator itself.

You may have trouble with the terminology difference of modulator and carrier. I certainly did when I first got into ring modulators. I remember it this way: the carrier is ever-present in the ring mod unit and the guitar/instrument input signal is modulating the ever-present carrier.

As we’ll discuss shortly, the effect of ring modulation doesn’t discriminate between modulator and carrier. However, to be technically correct, the carrier is the signal produced by the ring mod unit.

The Ring Modulation Effect

The output of the ring modulator is made of the sum and difference frequencies of the modulator and carrier waves. This is the same as with amplitude modulation except that ring modulation does not output the carrier signal nor does it output the modulator signal.

Note that some ring modulator pedals will have a wet/dry mix, which can re-introduce the dry/direct (carrier) signal. However, the ring mod circuit itself does not output the carrier (or the modulator) signals.

The easiest explanation is possible with a sine wave modulator and a sine wave carrier. Let’s say the modulator has a frequency (fm) of 1,500 Hz and the carrier has a frequency (fc) of 700 Hz. Remember that sine waves only have a single frequency.

The output of the ring modulator would have two new frequencies that are the sum and difference (sidebands) of the two input signals. They would be:

  • f1 = fm + fc = 1,500 + 700 = 2,200 Hz
  • f2 = fm + fc = 1,500 – 700 = 800 Hz

It’s important to note, before we get too into it, that the audible range of frequencies is 20 Hz – 20,000 Hz. Any sidebands outside of this range are typically filtered out of a ring mod unit since we cannot hear them, anyway! This helps free up headroom and prevents clipping.

Let’s further our understanding of the ring modulation effect by looking at a few other examples.

Let’s start off with sine wave carriers and modulators since they are easy to visualize.

In our first illustrated example, let’s have a 1 kHz sine wave modulator. The frequency response is shown below:

What happens if we send this modulator wave through a ring modulation circuit with a carrier wave also set as a 1 kHz sine wave? Remember that the output would be the sum and difference of the signals’ frequencies. Therefore, we’d have:

  • 1 kHz – 1 kHz = 0 Hz (no signal)
  • 1 kHz + 1 kHz = 2 kHz

The first sideband is 0 Hz and so the output will only have one frequency.

Note that the original 1 kHz modulator wave and the 1 kHz carrier are not present in the output signal. Rather, the 1 kHz modulator is simply outlined to represent the “instrument” input in the following graphs:

What happens if we use a 500 Hz sine wave as the carrier for our 1 kHz (1,000 Hz) modulator? We’d have:

  • 1,000 Hz – 500 Hz = 500 Hz
  • 1,000 Hz + 500 Hz = 1,500 Hz

In this case, the ring modulator acts as it’s supposed to, creating two new frequencies within the audible range, as shown below:

As another example, let’s see how a 900 Hz sine wave carrier signal will affect our 1 kHz (1,000 Hz) modulator:

  • 1,000 Hz – 900 Hz = 100 Hz
  • 1,000 Hz + 900 Hz = 1,900 Hz

That’s all good but guitar signals are not sine waves. They have a rather complex harmonic structure with different transient/envelope information for each harmonic (each harmonic will begin at a different amplitude and decay at a different rate). How would this work as a modulator signal?

We’ll get into the harmonic character of guitars later in this article.

For now, in order to get the basic idea, let’s look at a simpler wave: the triangle wave. Recall that the triangle wave has only odd harmonics and each successive harmonic has less amplitude than the last.

To keep things clean in this example, let’s limit the number of harmonics to 4.

We’ll use a 100 Hz triangle wave with only 4 harmonics as our modulator. The harmonics are at 300, 500, 700 and 900 Hz. This triangle wave is represented by the following frequency graph:

Let’s now look at how a ring modulator would affect this 100 Hz triangle modulator wave with a 50 Hz sine wave carrier.

Sidebands would be produced at each harmonic:

  • 100 Hz fundamental would become:
    • 100 – 50 = 50 Hz
    • 100 + 50 = 150 Hz
  • 300 Hz first harmonic would become:
    • 300 – 50 = 250 Hz
    • 300 + 50 = 350 Hz
  • 500 Hz second harmonic would become:
    • 500 – 50 = 450 Hz
    • 500 + 50 = 550 Hz
  • 700 Hz third harmonic would become:
    • 700 – 50 = 650 Hz
    • 700 + 50 = 750 Hz
  • 900 Hz fourth harmonic would become:
    • 900 – 50 = 850 Hz
    • 900 + 50 = 950 Hz

An 80 Hz sine wave carrier would cause the following:

  • 100 Hz fundamental would become:
    • 100 – 80 = 20 Hz
    • 100 + 80 = 180 Hz
  • 300 Hz first harmonic would become:
    • 300 – 80 = 220 Hz
    • 300 + 80 = 380 Hz
  • 500 Hz second harmonic would become:
    • 500 – 80 = 420 Hz
    • 500 + 80 = 580 Hz
  • 700 Hz third harmonic would become:
    • 700 – 80 = 620 Hz
    • 700 + 80 = 780 Hz
  • 900 Hz fourth harmonic would become:
    • 900 – 80 = 820 Hz
    • 900 + 80 = 980 Hz

Something interesting happens with a 100 Hz sine wave carrier. The upper sideband of one triangle wave frequency matches with the lower sideband of the following frequency. We could say that this ring modulator is “tuned”. It would look something like this:

  • 100 Hz fundamental would become:
    • 100 – 100 = 0 Hz (no audio)
    • 100 + 100 = 200 Hz
  • 300 Hz first harmonic would become:
    • 300 – 100 = 200 Hz
    • 300 + 100 = 400 Hz
  • 500 Hz second harmonic would become:
    • 500 – 100 = 400 Hz
    • 500 + 100 = 600 Hz
  • 700 Hz third harmonic would become:
    • 700 – 100 = 600 Hz
    • 700 + 100 = 800 Hz
  • 900 Hz fourth harmonic would become:
    • 900 – 100 = 800 Hz
    • 900 + 100 = 1,000 Hz

Ring modulators may sound very “harmonic” when the carrier and modulator signals are harmonically related and work together to boost harmonic partials of the input signal. Of course, the output frequency response will be different than either inputs. However, it may very well be similar, harmonically speaking.

When the carrier and modulator frequencies are not harmonically related (which is often the case with a guitar ring mod pedal), the effect will produce an inharmonic output. This is what gives the ring modulator its characteristic bell-like/metallic/strange sound.

If we brought the carrier sine wave up to 1,000 Hz to ring-modulate our 100 Hz triangle modulator wave, we might be thinking, by our previous calculations, that we’d have negative output frequencies (100 – 1,000 = –900, for example).

This is a perfect opportunity to discuss a key part of ring modulation: when it comes to frequency splitting, it doesn’t matter which signal is the carrier and which is the modulator. That being said, in a ring mod pedal, the guitar signal is always the modulator and the internally generated signal is the carrier.

The main point I want to make is that, to the ring mod (and to our ears), a “negative frequency” will perform just like a “positive frequency”. As we move a sideband across the 0 Hz threshold into the negative, the sideband will actually begin creeping up and once it passes the 20 Hz threshold or “–20 Hz”, we’ll begin hearing it again.

So, then we should look at the sidebands of the sine wave carrier and each of the modulator harmonics to get a better picture of what’s actually happening:

  • 1,000 Hz carrier and 100 Hz modulator fundamental sidebands:
    • 1,000 – 100 = 900 Hz
    • 1,000 + 100 = 1,100 Hz
  • 1,000 Hz carrier and 300 Hz modulator 1st harmonic sidebands:
    • 1,000 – 300 = 700 Hz
    • 1,000 – 300 = 1,300 Hz
  • 1,000 Hz carrier and 500 Hz modulator 2nd harmonic sidebands:
    • 1,000 – 500 = 500 Hz
    • 1,000 + 500 = 1,500 Hz
  • 1,000 Hz carrier and 700 Hz modulator 3rd harmonic sidebands:
    • 1,000 – 700 = 300 Hz
    • 1,000 + 700 = 1,700 Hz
  • 1,000 Hz carrier and 900 Hz modulator 4th harmonic sidebands:
    • 1,000 – 900 = 100 Hz
    • 1,000 + 900 = 1,900 Hz

So rather than having this:

The ring modulator will output this:

So a ring modulator will take each and every harmonic the carrier signal and output the sidebands produced from every harmonic of the modulator signal.

This is relatively simple to visualize with a single-frequency sine wave as the carrier but gets more difficult to imagine with multi-frequency carriers.

Many ring modulators will utilize a sine wave as their carrier signal. However, some will utilize other waveforms. This can get tricky. Let’s say the carrier is a square wave (with infinite odd-order harmonics). Each harmonic will cause its own sideband.

We can utilize the basic concept of additive synthesis to help us understand the effect of ring modulation more clearly.

With additive synthesis, each harmonic of a synthesized sound is produced by its own sine wave, dedicated to that frequency. So then, a more complex signal, like that of a guitar signal modulator or a square wave carrier, can be thought of as a collection of individual sine waves at different frequencies.

In this context, each individual frequency/sine wave of one signal (modulator or carrier) is affected by every frequency/sine wave of the other signal to produce sidebands. These sidebands, as we’ve discussed, must be positive (there are no “negative frequencies”) and they should fit within the audible range of human hearing (between 20 Hz and 20,000 Hz).

Modulating, say, a sawtooth wave (infinite even and odd-order harmonics) by a square wave (infinite odd-order harmonics) would yield very involved sidebands and a complex output, indeed.

The purpose of these exercises is to be thorough in our investigation of the ring modulation effect.

Guitar signals have complex harmonic profiles made even more interesting with polyphony (multiple notes at once in a chord) and with overdrive/compression/distortion (which adds harmonics to the signal).

For example, a major triad would have, at the very least, 3 different fundamental frequencies (though some notes may be doubled up in a guitar chord) along with all the harmonics that go along with these fundamentals. Each of these frequencies would be affected by the carrier and sidebands would be produced from each and every frequency.

Most ring modulators will use a sine wave carrier signal to keep the effect relatively “tame”. However, it’s important to understand how a square wave (or another waveform) would act as a carrier signal in a ring modulator.

A Discussion On Ring Modulation Waveforms

Ring modulation can also be visualized in terms of waveforms.

Let’s have a look at a sine wave carrier (top) with frequency x; a sine wave modulator (middle) with frequency 16x, and the resulting ring-modulated product (bottom):

Notice how the resulting product flips phase as the carrier becomes negative. This is part of ring modulation and the major difference between ring modulation and “regular” amplitude modulation.

By flipping the phase when the carrier is negative, the ring modulation circuit effectively eliminates the modulator signal from the output. As we’ll discuss shortly, this is the main difference between a ring modulation circuit and an amplitude modulation circuit.

Let’s now look at a sine wave carrier (top) with frequency x; a square wave modulator (middle) with frequency 16x, and the resulting ring-modulated product (bottom):

This process of “frequency mixing” in ring modulation is known as heterodyning. A heterodyne is a signal frequency that is created by combining or mixing two other frequencies together.

This “splitting” of the signals’ frequencies/harmonics is possible to achieve via analog means. Some distortion may occur due to the forward voltage drop of the diodes. However, this multiplication is much easier (and cleaner) in digital systems using rather simple DSP.

By that token, we can have either analog or digital ring modulation pedals. Most ring modulation pedals, though, are analog.

The Electro-Harmonix Frequency Analyzer XO (link to check the price on Amazon) is a great example of an analog ring modulator pedal.

Electro-Harmonix Frequency Analyzer XO

The Strymon Mobius (link to check the price on Amazon) is a digital multi-effect pedal focused on modulation-type effects. It has an awesome ring modulation setting accessed via the AM (amplitude modulation) mode in its Quadrature mod machine type.

Strymon Mobius

Electro-Harmonix and Strymon are both featured in My New Microphone’s Top 11 Best Guitar/Bass Effects Pedal Brands To Know & Use.

Ring Modulator Vs. Voltage Controlled Amplifier

If you happen to be coming from a more synthesizer-based background of understanding, perhaps relating a ring modulator to a VCA could help develop your knowledge of ring modulation.

A VCA allows one signal to pass when another signal is “present”. In the case of a VCA, the control voltage signal (analogous to the “carrier”) is in charge of passing the audio input signal (analogous to the “modulator”).

VCAs are often controlled by envelopes or LFOs (low-frequency oscillators) in order to shape the amplitude of a synth patch.

If the control voltage/modulator is maxed, the entire carrier is passed through. If either the CV or the input signal are at 0 volts, there will be no output.

If the CV is negative (below 0 volts), then no carrier signal shall pass through to the output.

Here’s an illustration of a VCA signal flow graph:

VCAs are called 2-quadrant multipliers because they handle both positive and negative voltages/amplitudes in the audio/carrier input, but only positive voltages/amplitudes on the modulation input. This results in no output when the modulator runs at and below 0 volts.

Ring modulators, by contrast, are referred to as 4-quadrant multipliers or “balanced modulators” since they can negative and positive voltages/amplitudes in both the carrier and modulator input signals.

Like the VCA, the ring modulator’s carrier signal “allows” the modulator to pass at various amplitudes. However, when the carrier drops to a negative voltage/amplitude, it still passes the modulator.

The catch here is that the phase of the modulator is inverted when the carrier is negative. Remember that we’re multiplying signals and multiplying a negative by a negative yields a positive while multiplying a negative by a positive yields a negative.

Here’s an illustration of a ring modulator signal flow graph:

To further visualize the differences between a VCA and a ring modulator, let’s look at illustrations of waveforms.

Below, we have a representation of a VCA to the left and a ring modulator to the right.

The VCA has a sine wave CV with frequency x (top) while the ring modulator has a sine wave carrier with frequency x (top). Each has audio/modulator signals with a frequency 8x (middle). The difference in output signals (at the bottom) are shown:

As another example, we have a VCA to the left and a ring modulator to the right. This time there is a sine wave CV/carrier with frequency x (top) and a square wave audio/modulator with a frequency 8x (middle). The output signals (at the bottom) are shown:

Ring Modulation Vs. Amplitude Modulation

Another great way of describing ring modulation is to contrast it against straight-up amplitude modulation.

Amplitude modulation is often used to produce a tremolo effect when its carrier signal frequency is the LFO range (from well below 1 Hz to under 20 Hz). Amplitude modulation is also used in AM radio, where the carrier signal frequency in the AM radio range (about 550 to 1720 kHz).

Ring modulation and amplitude modulation are similar but not exactly the same.

The key difference in the resulting output between RM and AM is that AM keeps the original modulator signal frequencies in the output. Ring modulation, as we’ve discussed, removes the original modulator frequencies from the output, leaving only the sum and difference frequencies of the carrier and modulator.

This happens because a ring modulator’s carrier signal will actually go into negative and affect the polarity of the modulator signal.

A regular amplitude modulation carrier will remain positive and simply acts to modulate the peaks/troughs (amplitude) of the modulator wave. This unipolar carrier (which means the entirety of the signal is above 0 V) is made possible by applying a positive DC offset voltage to the carrier signal.

Below, we have a representation of RM to the left and AM to the right. Each has a sine wave carrier with frequency x (top) and a modulator with a frequency 8x (middle). The difference in output signals are shown at the bottom:

Notice that the 0 volts line (the horizontal black line) is different on the carrier signal of the AM illustration. This represents the unipolar nature of the AM modulator wave. The entirety of the AM carrier is above 0 V while the RM carrier is negative half the time.

Here, we have another representation of RM to the left and AM to the right. Each has a sine wave carrier with frequency x (top) and a square wave modulator with a frequency 8x (middle). The difference in output signals are shown at the bottom:

That was a lot of information. Let’s recap to help simplify!

Ring modulation has two inputs and one output.

The first input is called the modulator and is generally the audio signal. This is the case with ring modulation guitar pedals.

The second input is a bipolar waveform generated by the ring mod unit. It’s generally a basic waveform (most often a sine wave) and has a frequency in the audible range, most often sweepable in the range of 20 Hz to 4,000 Hz.

The output of the ring modulation circuit is made of the sidebands of these two input signals. Sidebands are made from sum and difference between each frequency of the modulator and each frequency of the carrier.

A sine wave (single frequency wave) carrier will produce two sidebands with each harmonic/fundamental frequency of the modulator input signal.

A square wave (or another more harmonically complex carrier wave) will produce many sidebands with each harmonic/fundamental frequency of the modulator input signal.


What Are Ring Modulation Pedals & How Do They Work?

Now that we understand what ring modulation is, let’s get into ring modulation pedals and how they work.

A ring modulation pedal is simply a ring modulation unit with the form factor of an instrument stompbox. These pedals are typically designed for guitar signals but can also work on other instruments. They also generally have controls to alter their functionality, which we’ll get to momentarily.

Once again, the ring modulation circuit gets its name from its basic layout which looks like a ring of clockwise (or counter-clockwise) diodes.

The basic ring modulation circuit resembles the following:

This image has an empty alt attribute; its file name is mnm_Basic_Ring_Modulation_Circuit.jpeg

There are two inputs and one output in the basic ring mod circuit:

  • Modulator (input)
  • Carrier (input)
  • Output

Ring Modulator Input: Modulator

The input signal (also known as the modulator) is the guitar signal.

Ring Modulator Input: Carrier

The input signal produced by the ring modulation pedal is referred to as the carrier. This carrier signal is either produced digitally or via a voltage-controlled oscillator and is typically a sine wave or another basic wave shape.

A ring mod pedal will allow us to alter the frequency on the VCO/carrier signal and some even allow us to change the sine wave to another waveform (often a square wave).

Like the carrier of an AM radio signal, this carrier wave is ever-present (when the pedal is turned on) and is ready to be modulated by the modulator (guitar input) signal.

A ring mod pedal will generally offer a large range of possible carrier frequencies. We can typically sweep through this range via a “frequency” knob.

Some ring mod pedals even have a “low” function that drops the carrier frequency down into the LFO (low-frequency oscillator) range, allowing the pedal to double as a sort or tremolo.

Ring Modulator Output

The output of the ring modulation circuit is made of the sidebands (sum and difference) of the input/modulator signal and carrier signal frequencies.

The Harmonic Profile Of A Guitar Signal

As we’ve discussed, the ring modulation pedals are typically designed for guitar signals. Let’s briefly discuss the harmonic content of a guitar signal.

Know that different instruments have different harmonic profiles and frequency responses. These differences give the various instruments their unique timbres/tones even when they play the same exact note.

There are plenty of ways to alter a guitar’s tone (EQ, wah, compression, distortion, modulation). Any change in signal tone going into the ring modulator will yield a difference in sidebands due to the alteration in the guitar’s frequencies.

That all being said, a vibrating guitar string will produce both odd and even-ordered harmonics.

Generally the first harmonic (an octave above the fundamental) will be the highest in amplitude. The fundamental frequency and second and third harmonic will typically be a bit lower in amplitude but very present in the signal.

Above the third harmonic, each successive harmonic has less amplitude that the one before it. This goes on until about the 16th harmonic, where the following harmonics get a slight boost in amplitude.

Above the 24th harmonic, the amplitudes become so low that they’re barely identifiable. Harmonics well before the 24th are largely ignored in analysis though they are responsible for the timbre of the vibrating guitar string.

Even harmonic will have its own amplitude envelope as part of the string’s timbre. The higher harmonics will die out much fast than the fundamental and lower harmonics, which sustain as the string continues to vibrate.

Of course, this is just the basics of a vibrating guitar string. Factors such as the guitar body material; string material and tension; note(s) being played; electromagnetic pickup; tone and volume control; patch cable; other effects units; amplifier(s), and others will affect the actual frequency response of the guitar.

A 6-string guitar in standard tuning will have its lowest fundamental frequency at 82 Hz at E2 (the open low E string). Most pickups will have a frequency response extending to 8 kHz or lower in the high-end. Most amplifiers and cabinets will cut high frequencies even below that.

So if we have a ring modulator pedal with a sine wave carrier, we’ll get two sidebands for each of the guitar’s partials/harmonics. These harmonics and fundamental frequencies will generally be within the range of 82 Hz to about 8,000 Hz.

A square wave carrier will produce many more sidebands and may cause an overly distorted sound at the output given the already-rich harmonic nature of a guitar signal.

The Ring Modulation Circuit

Without getting into the weeds of particular schematics, let’s look at the basics of the ring mod circuit. To help us visualize, I’ll bring back the circuit illustration for a third time:

This image has an empty alt attribute; its file name is mnm_Basic_Ring_Modulation_Circuit.jpeg

The 4 clockwise-facing diodes are effectively set up as 2 pairs. One pair is made of the “top and bottom” diodes while the other is made of the “left and right” diodes.

As the bipolar (AC) carrier signal alternates between positive and negative current, it will cause, at any given time, one pair of diodes to conduct electricity while reverse-biasing the other pair.

It is the conducting pair that allows the modulator (input) signal to travel from the secondary transformer winding at the input to the primary transformer winding at the output.

When the carrier signal is in the positive part of its waveform, it causes the top/bottom pair of diodes to conduct based on the amplitude of the carrier. This allows the modulator to pass but restricts its amplitude to the waveform of the carrier.

When the carrier signal is in the negative part of its waveform, it causes the left/right pair of diodes to conduct based on the amplitude of the carrier. This allows the modulator to pass with restricted amplitude (based on the amplitude of the carrier) but flips the polarity between the transformers.

Once again, this can be visualized in the following illustration where the carrier sine wave (top) affects the amplitude and polarity of the modulator square wave (middle) to produce the output (bottom). Notice the polarity shift in the output as the carrier dips below 0:

This image has an empty alt attribute; its file name is mnm_Ring_Mod_Sine_On_Square-2.jpeg

This causes the ring modulation circuit to eliminate the modulator signal frequencies from the output and effectively splits the frequencies between the modulator and carrier signals at the output.

Note that other ring modulation units may utilize digital signal processing (DSP) in order to achieve the same effect. Here, the frequencies of the two inputs are detected and used to mathematically sum and subtract the two output frequencies.

Low-pass filters and oversampling are often used in digital ring mods to avoid aliasing and distortion in the output signal.


The Control Parameters Of Ring Modulation Pedals

Let’s now turn our sights onto the common control parameters we’ll find on a ring modulation pedal. This will give us further insight into how ring modulation pedals are designed and how they function as effects units.

Common ring modulation pedal controls include:

Carrier Frequency

The carrier frequency control is rarely ever labelled as “carrier frequency”. However, it’s always a parameter we can control on a ring modulation pedal.

As the descriptor suggests, the “carrier frequency” control will alter the frequency on the carrier signal (which is either a sine or another basic waveform).

The frequency range of a ring mod carrier is in the audible range of frequencies, typically in the lower range between about 20 Hz to 4,000 Hz (rather than all the way to upper audible limit of 20,000 Hz).

These controls are often labelled simply as “frequency”. Other pedals offer coarse and fine-tuning adjustments for the carrier frequency.

The Electro-Harmonix Ring Thing (link to check the price on Amazon) offers both coarse and fine tuning of its carrier frequency.

Electro-Harmonix Ring Thing

High/Low (Speed)

In our discussion of general amplitude modulation, we touched on the similarities between tremolo and ring modulation.

To recap, tremolo is essentially ring modulation with a very low carrier frequency. Ring modulation, then, is pretty much the same as tremolo only with a much faster “LFO”. While we can actually hear the modulation of the amplitude in tremolo, we hear the AM of ring modulation as an alteration of harmonic content.

To improve functionality, some ring mod pedals offer a “tremolo setting” by allowing users to toggle between a “high-frequency” carrier and a “low-frequency” carrier (LFO). Note that each setting will have its own range that we can sweep through with the aforementioned carrier frequency control.

The Fairfield Circuitry Randy’s Revenge (link to check the price on Amazon) allows us to toggle between a ring modulation carrier frequencies (HI) and tremolo LFO frequencies (LO). The frequency control (FREQ) applies to both

Fairfield Circuitry Randy’s Revenge

Wave

As we’ve discussed, most ring modulation utilizes a simple sine wave as its carrier frequency. These single-frequency waveforms offer a single split of each harmonic/partial of the input (modulator signal).

However, for those ring mod pedals that offer options for the carrier wave, there will be a control that allows us to toggle between the various carrier waveforms.

The frequency can be altered for each carrier waveform.

The Way Huge Ringworm (link to check the price on Amazon) offers a whopping 5 different modes with 3 different carrier waveforms, an envelope and random.

Way Huge Ringworm

Filter

The frequency multiplying/splitting can get rather convoluted in the high-end of the pedal’s output.

Remember that harmonics are integer multiples but the frequency spectrum is logarithmic. Therefore, the upper octave(s) will have more harmonic content. Sometimes this content is overly harsh and ill-defined. A low-pass filter can effectively rid of this information and clean up the signal.

Note that guitar pickups will often only have a frequency response up to 6 – 8 kHz so the high-end information is not typically heard anyway. It’s okay, then, to filter it out!

Mix

Some ring modulation pedals do allow us to mix the dry/direct signal back in with the output of the ring mod circuit. This brings up closer to a typical amplitude modulation output.

LFO Section

Some ring modulation pedals will have a separate low-frequency oscillator (with frequency, waveform and amplitude controls).

This LFO is generally used to modulate the carrier frequency and, therefore, the output frequencies of the ring mod circuit output.

The Moog Moogerfooger (now discontinued) has an entire section dedicated to its LFO.

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Tips On Using Ring Mod Pedals

Ring modulation pedals are certainly strange. They may even be downright troublesome to get a usable sound out of.

Here are a few tips to get the most out of your ring modulation pedal:

Set The Carrier Frequency To Match The Key

Ring modulation is known for being rather “inharmonic” and “unmusical”. However, we can “tune” these pedals to become somewhat harmonic within a limited range of notes.

We can do so by adjusting the carrier frequency to match the fundamental or lower harmonic of the notes we’re playing.

Let’s say we’re playing in the key of A (the open A string of a guitar has a fundamental frequency of 110 Hz in A4 = 440 Hz tuning). Setting the ring mod carrier frequency to 110 Hz should give us a harmonic/musical sound so long as we stay within the constraints of A and its first few harmonics.

In the example of A 110 Hz, we’d have the following harmonics:

  • Fundamental: 110 Hz (A2) = root
  • 1st harmonic: 220 Hz (A3) = root
  • 2nd harmonic: 330 Hz (E4 – 2 cents) = perfect fifth
  • 3rd harmonic: 440 Hz (A4) = root
  • 4th harmonic: 550 Hz (C#5 + 14 cents) = major third
  • 5th harmonic: 660 Hz (E5 – 2 cents) = perfect fifth

So long as we stay within the confines of the root, perfect fifth and major third, the output of the ring mod should remain pretty harmonic.

To learn more about the relationships between musical notes and frequencies, check out my article Fundamental Frequencies Of Musical Notes In A=432 & A=440 Hz.

Double It As A Tremolo Pedal

As mentioned, some ring modulation pedals offer a “low-frequency setting” in which their amplitude-modulating circuit becomes a tremolo rather than a ring mod.

It should come to no surprise that ring modulation isn’t an effect we typically leave on like, say, a compressor. So then, when we aren’t needing the ring mod effect, we can set the pedal to “tremolo mode” and get a two-in-one effect.

Bring In Some Direct Signal

If the ring mod pedal offers any sort of mix control, we can dial in some of the direct signal.

By dialing in some dry signal, we can effectively hear the actual notes we’re playing. This can also make the effect less pronounced in the overall mix, making it more of an accent than a main attraction in your playing.

Express Yourself

If the ring modulation pedal has an expression input, use it!

Being able to control the carrier frequency or LFO of the ring mod pedal can really be a great benefit in getting the most out of the strange effect.

Read The Manual

In all likelihood, the pedal manufacturer’s manual will tell you more about the specific ring modulation capabilities of the pedal than this article ever could.

Reading the manual can give you great insight into the pedal and how to get the most out of it. It may even give you the knowledge required to dial in settings exactly how you hear them in your head!

Play To The Pedal

Ring modulation is a strange effect. Sometimes strange effects need strange riffs/lines to reach their full potential.

Wonderwall will likely sound awful through a ring modulator. However, writing something weird could fit perfectly with the ring mod effect.

Playing to the pedal is something I also suggest for synth pedals when Blues licks just don’t do the effect justice.

By playing to the pedal, we can open up a whole new realm of creativity centred around our ring mod pedal.


Where Should A Ring Modulation Pedal Go In The Signal Chain?

Ring modulation pedals sound pretty experimental and so my advice is to experiment with positioning in the pedal chain.

Modulation effects often sound best near the end of the pedal chain just before time-based effects (delay and reverb). However, ring modulation pedals aren’t our typical modulation effects pedals (chorus, flanger, phaser, etc.).

I’ve gotten cool results using a ring mod at the very end of the chain (yes, even running delay into it). I’ve also gotten cool results with it at the front of the chain and in the middle.

Chances are that the ring mod pedal will be used sparingly for special effect rather than as a mainstay in your tone. Therefore, it can be fun to experiment with its placement to get the coolest effects possible.

If your ring mod pedal doubles as a tremolo pedal and you plan on using it as both, then perhaps putting it after the dynamic, pitch-shifting, synth and gain-based effects would work best. This still allows for plenty of placement options, especially with larger signal chains.

To learn more about ordering pedals in the signal chain, check out my article How To Order Guitar/Bass Pedals (Ultimate Signal Flow Guide).


Other Amplitude-Modulation Effects

Now that we’ve discussed ring modulation pedals and how they work, essentially, as amplitude-modulators. Let’s have a look at other pedals that alter the amplitude of the signal to produce their effects.

Other pedal types that are designed primarily to alter the amplitude of the signal are:

Note that many pedals will have volume/level controls. However, most pedals aren’t designed with to affect amplitude specifically.

Tremolo Pedals

Tremolo pedals can be though of as ring modulation pedals with LFOs (low-frequency oscillators) rather than modulation signals in the audible frequency range.

The LFO of a tremolo pedal alters the amplitude of the signal, bringing the signal up and down in level. It does so at a rate that is heard as actual amplitude modulation rather than as an additional pitch (as is the case with ring modulation).

Technically speaking, even an LFO-range carrier frequency will split the input into two sets of harmonics. However, the frequency difference and sum between the two sets is so small that we don’t hear it as a difference in pitch.

That being said, the effect of tremolo can be heard as altering the amplitude of the signal at a fast rate.

The Electro-Harmonix Stereo Pulsar (link to check the price on Amazon) is an example of a stereo tremolo pedal.

Electro-Harmonix Stereo Pulsar

To learn more about tremolo pedals, check out my article What Are Tremolo Guitar Effects Pedals & How Do They Work?

Volume Pedals

Volume pedals are generally designed as expression pedals (with treadle-type foot controller). They control to volume or amplitude of the signal passing through their circuit.

This volume control is achieved by means of attenuation rather than by applying gain.

Volume pedals are easy to understand. The expression pedal will allow maximum signal in either toe-down or heel-down position and no signal at the opposite position, depending on how the pedal is set up.

Volume pedals do not only allow for muting, which is great between songs, while tuning, etc. They also allow for volume swells and other changes in dynamics due, in large part, to their continuously variable nature.

The Ernie Ball VP JR. (link to check the price on Amazon) is a popular volume pedal with a relatively small footprint (hence the name “Jr.”).

Ernie Ball VP JR.

Is chorus a modulation effect? Chorus is considered to be a part of the modulation category of effects. It utilizes a modulated delay circuit to produce pitch-variation in the wet signal and combines the wet and dry/direct signals at the output to produce a multi-voice “chorus” effect.

What is the difference between chorus and flanger? Chorus and flanger are both based on the same basic design: a modulated delay circuit that causes phase modulation in the output signal (a mix of the wet and dry signals). The chorus effect sounds like multiple voices with slight detuning while the flanger effect sound like a whooshing/sweeping of the phase. The major differences in design are:

  • Flangers typically only use two voice (wet and dry). Chorus may have multiple wet voices (though a 2-voice effect is also common).
  • Flangers have shorter delay times (below 10 ms) while choruses have longer delay times (above 10 ms). There is crossover between these values.
  • Flangers utilize a feedback loop in the delay circuit while choruses do not.

To learn more about chorus and flanger pedals, check the following My New Microphone articles, respectively:
What Are Chorus Pedals (Guitar/Bass FX) & How Do They Work?
What Are Flanger Pedals (Guitar/Bass FX) & How Do They Work?

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