Synthesis 101 | Introduction to Control Voltage (CV)

TABLE OF CONTENTS

Introduction to Control Voltages
Controlling Your Modular Synth with the CV Output of a MIDI Keyboard
Clocking Between Multiple Semi-Modular Synthesizers
Bipolar & Unipolar Voltage
Attenuator & Attenuverter
CV Offset
CV Guidelines (Voltage Height Standards)

Introduction to Control Voltages

Control voltages (CV) are a fundamental aspect of analog synthesis, allowing musicians and sound designers to manipulate various parameters of their synthesizers and other electronic instruments. In essence, CV is a voltage signal that can control different functions, such as pitch, filter cutoff, and modulation depth. By using CV, you can create dynamic and expressive sounds that evolve over time, making it an essential tool in the world of electronic music.

In analog synthesis, control voltages are typically generated by sequencers, keyboards, or other devices, and they can be routed to different modules or hardware to control their behavior. Understanding how to effectively use CV can greatly enhance your creative possibilities and enable you to explore new sonic landscapes.

Controlling Your Modular Synth with the CV Output of a MIDI Keyboard

Using a MIDI keyboard to control your modular synth can be useful if the synth does not have keys. Most MIDI keyboards with CV capabilities come equipped with CV (Control Voltage) outputs, which can be used to interface with analog synthesizer modules. The three primary CV outputs you’ll find on a MIDI keyboard are gate, velocity, and pitch. Here’s how to connect each of these outputs to your modular synth.

Gate

The gate output is typically used to trigger notes. When you press a key on your MIDI keyboard, the gate signal sends a high voltage (usually +5V) to the connected module, indicating that a note should be played. This output can be connected to the "Gate" or "Trigger" input of your synthesizer module. Typically, this is introduced to the envelope generator assigned to the VCA. Many envelope generators and VCA (Voltage Controlled Amplifier) modules have gate inputs that respond to this signal, allowing you to shape the sound dynamically.

Pitch

The pitch CV output is crucial for controlling the pitch of your synthesizer. This output sends a continuous voltage that corresponds to the notes played on your keyboard. Connect this output to the "1V/Oct" input on your oscillator module. Most analog oscillators are designed to interpret this voltage as musical pitch, allowing you to play melodies and harmonies directly from your MIDI keyboard.

Velocity

The velocity output conveys how hard or soft you play the keys, translating this information into a control voltage. This output can be connected to various parameters on your synth, such as filter cutoff or modulation depth, allowing for expressive performance. Look for inputs labeled as "Velocity" or "Modulation" on your modules. By connecting the velocity CV output, you can create more nuanced sounds that respond to your playing style.

Clocking Between Multiple Semi-Modular Synthesizers

Connecting semi-modular synthesizers can be a fun approach to delve into sound design and unique sound designs. Typically, syncing the tempo between hardware is the initial patch that most users establish to guarantee effective hardware gain staging.

Setting up the Master Clock

When using several semi-modular synthesizers, it’s crucial to designate one as the master clock. The master clock acts as the timing reference for all other devices, ensuring they remain in sync. The synthesizer that you intend to control the tempo or rhythm will serve as your master clock. To configure this, link the clock output of the master synthesizer to the clock input of the other synthesizer(s).

For example, if you select the Subharmonicon as your master clock, you would connect its CLOCK OUTPUT to the TRIGGER INPUT of the DFAM. This enables the DFAM to adhere to the tempo established by the Subharmonicon. You can also utilize the TRIGGER, SEQ 1 CLK & SEQ 2 CLK OUTPUTS of the Subharmonicon instead of the CLOCK OUTPUT for a different sync response.

If you wish to reverse the clock so that the DFAM takes on the role of the master clock, connect the TRIGGER OUTPUT of the DFAM to the CLOCK INPUT of the Subharmonicon.

Bipolar & Unipolar Voltage

What is Unipolar Control Voltage?

Unipolar control voltages range from 0 volts to a positive maximum voltage, typically 5V or 10V. This type of CV is commonly used in synthesizers for controlling parameters such as pitch, filter cutoff, and modulation depth. Since unipolar CVs only move in one direction (positive), they are ideal for parameters that do not require negative values. For instance, when controlling the frequency of an oscillator, a unipolar CV can effectively dictate the pitch without the need for negative voltages.

Applications of Unipolar CV

Oscillator Tuning: Unipolar CVs are often used to set the pitch of oscillators, ensuring that the output remains within a specific tonal range.
Filter Control: When adjusting filter cutoff frequencies, unipolar CVs allow for smooth transitions without the risk of negative values causing unwanted effects.
Envelope Generators: Unipolar CVs are frequently utilized in envelope generators to control the amplitude of sound over time, providing a clear and predictable output.

What is Bipolar Control Voltage?

Bipolar control voltages, on the other hand, can range from a negative voltage (-5V) to a positive voltage (+5V). This allows for a wider range of modulation possibilities, as both positive and negative values can influence parameters. Bipolar CVs are particularly useful for controlling aspects of sound that require both upward and downward modulation, such as pitch bending or modulation effects.

Applications of Bipolar CV

Pitch Modulation: Bipolar CVs are ideal for pitch modulation, allowing for both sharp rises and falls in pitch, which can create expressive musical phrases.
LFO Control: Low-Frequency Oscillators (LFOs) often utilize bipolar CVs to modulate effects like vibrato or tremolo, providing a richer and more dynamic sound.

Attenuator & Attenuverter

An attenuator is a module that allows you to control the amplitude or volume of a signal. It essentially acts as a volume knob, allowing you to decrease the level of a signal before it reaches another module. This can be useful for controlling the dynamics of your sound or for creating more subtle changes in volume. If you want to control the depth of modulation on a synthesizer parameter (like filter cutoff or oscillator pitch), patching a CV signal to an attenuator allows you to fine-tune the modulation intensity. This is particularly useful when you want subtle changes rather than drastic shifts.

An attenuverter, on the other hand, not only allows you to attenuate a signal but also invert it. This means that you can not only decrease the volume of a signal but also flip it upside down, creating interesting and unique modulation possibilities. Attenuverters are commonly used in modulation sources like LFOs and envelopes to add more depth and complexity to your sound. If you have an LFO (Low-Frequency Oscillator) controlling a filter, you can invert the LFO signal with the attenuverter to achieve unique rhythmic effects that can add interest to your sound.

CV Offset

A CV offset refers to a fixed voltage added to a control voltage signal. This offset can shift the entire range of the CV signal, allowing for more nuanced control over your synthesizer's parameters.

When you apply a CV offset, you are essentially altering the baseline level of the control voltage. For example, if you have a CV signal that ranges from 0V to 5V, adding a +1V offset would shift the range to 1V to 6V. This means that the lowest value of your control signal now starts at 1V instead of 0V, effectively changing the starting point of modulation.

CV offsets allow you to fine-tune parameters without needing to adjust the entire signal. This is particularly useful in complex patches where precise control is required.

CV Guidelines (Voltage Height Standards)

While working with control voltages, it’s crucial to adhere to the specified voltage limits of your instrument's CV inputs.

Sending lower than expected voltages can result in an inconsistent sound. For example, if your VCA requires +10V but your modulation source is sending +5V, it will never reach the full extent of it's output amount.

Sending higher voltages than these limits won't damage your instrument in the short term; however, consistently exceeding these limits without proper attenuation can lead to long-term durability issues. To ensure the longevity of your gear, always use appropriate voltage levels as indicated in your instrument’s manual.

For a complete list of CV patch points and their acceptable voltage ranges, please refer to your instrument’s manual. This resource will provide you with the necessary information to safely and effectively utilize CV in your setup, ensuring a smooth and enjoyable synthesis experience.