This is an extract from our Demystifying Voltage booklet also available in our limited edition book Eurorack Introductory Collection.
Before diving into the intricate world of Eurorack modular synthesis, it's crucial to comprehend the fundamental concepts of electricity and voltage.
Electricity
Electricity is the flow of electric charge, typically carried by electrons in conductive materials like metals. This flow is initiated by a potential difference or voltage. For electricity to flow, there must be a complete circuit, a closed loop through which the electrons can move.
In a circuit, various components influence the flow of electricity:
• Resistor: Restricts the flow of current
• Capacitor: Stores and releases electrical energy
• Inductor: Stores energy in a magnetic field
• Diode: Allows current to flow in only one direction
• Transistor: Controls the flow of current
Understanding Voltage in Eurorack: The Driving Force
Voltage, often referred to as electric potential difference, is the force that propels electric charge to move through a conductor. It's measured in volts (V). Voltage is analogous to the pressure in a water pipe; the higher the voltage, the more force there is pushing the electrons through the circuit.
Control Voltage
Control Voltage (CV) is a fundamental concept in modular synthesis, acting as a means to transmit information and control parameters between modules. In Eurorack, CV typically ranges from -5V to +5V, so 10 volt peak to peak.
CV as a Control Signal
In the realm of Eurorack modular synthesis, Control Voltage (CV) is the silent conductor that directs the orchestra of modules. CV, in its simplest form, is voltage used to guide and manipulate parameters within a module. The magnitude of this voltage, whether high or low, holds the key to modulating and shaping a parameter of a module with a CV input in remarkable ways.
Imagine CV as a wizard's wand; the higher the voltage you wield and cast into a CV input of a module, the more potent and impactful the magic becomes. A surge of high voltage signifies a strong directive to the module, resulting in a robust and pronounced alteration of the associated parameter. Conversely, gently tapping a small amount of voltage into a CV input is akin to a subtle suggestion—a gentle nudge that delicately influences the module's behavior, allowing for fine-grained control and nuanced adjustments.
In essence, CV is the language spoken between modules, a silent conversation where the voltage levels translate into actions. Understanding this language empowers you to precisely choreograph the intricate dance of your Eurorack modules, bringing your sonic symphony to life, one voltage pulse at a time.
CV Sources and Destinations
Modules that generate CV signals are called CV sources, while those that receive and respond to CV are destinations. For instance, an LFO (low-frequency oscillator) generating a waveform can be a CV source, and a filter module responding to the LFO's CV to modulate cutoff frequency using the related input is a destination. Most modules can be CV sources. Conversely, an LFO can also be a destination if it has a CV input.
Sine Wave and its Role in Eurorack
The sine wave is a voltage signal, the fundamental waveform in audio synthesis (and in the world in general as it is theoretically the basis of all sounds), characterized by its perfectly smooth, rounded shape. It plays a pivotal role in shaping sound and generating control signals within a Eurorack system. When utilizing a slow, inaudible sine wave from an LFO to modulate the cutoff CV input of a filter, the cutoff will increase during the wave's ascent and decrease during its descent.
Generating and Using Sine Waves
Sine waves can be generated in Eurorack using dedicated oscillator modules. These modules produce a continuous and pure sine wave signal, serving as a fundamental sound source in a modular setup, but not only that.
When the signal transitions between ascents and descents at an extremely slow pace, it remains imperceptible and inaudible; the waveform lacks the speed necessary to produce sound. That’s what we mean by invisible. This silent voltage can be applied to a module's CV input, enabling you to control a parameter.
This aspect is fundamental to modular synthesis because any signal can be employed to manipulate a parameter when directed to an appropriate input.
Employing a slow sine wave on the filter's cutoff input initiates a measured alteration of the parameter linked to the cutoff knob, emulating a manual adjustment done by hand but executed internally, mechanically, and subtly. That’s what we mean by invisible hands. The movement in this scenario will be deliberate and gradual. On the other hand, applying a fast sine wave will swiftly move the cutoff parameter invisibly, resulting in rapid and energetic adjustments that would be impossible to replicate manually.
As a sine wave signal accelerates, it eventually reaches a threshold where audible sound becomes perceivable. This phenomenon is termed audio rate. This audio signal serves a dual purpose: it can be used for generating sound and for modulating a module's parameter.
Applying Sine Waves for Control
Sine waves generated by oscillators can be utilized as control signals. For instance, a sine wave can modulate the pitch of another oscillator, resulting in frequency modulation (FM), producing rich and dynamic timbral changes.
In simpler terms, if a slow sine wave is sent into the FM input of an oscillator, the oscillator frequency will rise and fall in sync with the slow sine wave's speed. Things get truly fascinating when you feed a fast sine wave into the FM input.
Pitch: Voltage as a Musical Translator
Pitch is a fundamental element in music, and in Eurorack modular synthesis, voltage serves as the precise force that sets and controls musical notes, allowing you to sculpt melodies and harmonies with incredible accuracy.
In Eurorack, voltage is a musical translator, converting electrical signals into specific musical notes. The standard convention is 1 volt per octave (1V/Oct), meaning for every 1-volt increase in voltage, the pitch shifts up by one octave. This precise voltage control forms the foundation for setting and modulating musical notes in your modular system.
Oscillators are the sound generators in your Eurorack setup, and they rely on voltage to determine the pitch of the produced sound. By sending a specific voltage to the pitch input, you can set the musical note you want to hear with remarkable accuracy. This level of control allows you to craft melodies that resonate with your artistic vision.
Offset and Its Influence on Voltage
Offset is an important concept in modular synthesis, representing a constant voltage added or subtracted from a signal. It has significant implications for shaping and controlling the behaviour of CV and audio signals and has the quality of demonstrating how CV can be manipulated to allow you to turn your modulation intention into reality.
This alteration shifts the signal's position on the voltage axis (up or down) without changing its shape. Offset modules generate this constant voltage, and it's used to control pitch, modulate parameters, adjust signal levels, and fine-tune control voltages within the modular system.
Generating and Understanding Offset
Modules capable of generating offset allow users to define a precise voltage level that can be added to or subtracted from an incoming CV or audio signal.
For instance, envision applying a 2-volt offset signal to a sine wave signal using the FM input of the oscillator responsible for generating the sine wave. If the sine wave typically oscillates between -5 volts and +5 volts, introducing a constant offset signal of +2 volts would shift the sine wave's range, resulting in oscillations between -3 volts (-5V + 2V = -3V) and +7 volts (5V + 2V = 7V).
This adjustment alters the baseline voltage level, influencing how the signal interacts with other modules. Offset finds various applications in Eurorack modular synthesis:
• Pitch Shifting: Applying an offset to a pitch CV can transpose a melody or sequence.
• Amplitude Control: Adjusting the offset can regulate the volume or intensity of an audio signal.
• Parameter Modulation: Offset can modulate parameters such as filter cutoff or resonance to achieve dynamic changes in sound.
Understanding these foundational concepts of electricity, voltage, pitch, sine waves, and offset is crucial for mastering the complexities of Eurorack modular synthesis. These principles underpin the creation of diverse and innovative soundscapes in the modular domain.
Would you like to know more about control voltage?
We cover all the basics and fundamentals of Eurorack modular synthesis, particularly control voltage, in our Demystifying Voltage booklet, which is also included in the complete collection of our three booklets: Eurorack Introductory Collection.