What is Control Voltage (CV)?

Control Voltage (CV)

In a modular synthVarious parameters can be controlled by voltage as well as knobs and buttons.For example, filter modules often have a jack to control the cutoff frequency with a voltage so that the cutoff frequency increases when the voltage of the patch cable pointed to changes from (for example) 1V (volt) to 5V. It has become.

This section describes the control voltage, Control Voltage (CV), using standard synth patching as an example. 

By the way, there are a lot of modular images patched below, but this one"modular grid"It is an image made on the site. In the modular grid, you can create your own virtual rack with modules using a huge database of modules and save it online. It also calculates the amount of current in the modular system automatically, so you can use it as a note for your setup, as a note for your setup, or as a patch note like the one below. I highly recommend it, so please take an account and play.

Patch 1

Oscillator → VCA

Now, this is where I put two modules in a rack and put two patch cables in. On the leftOscillator module Of Make Noise STO, RightVCA (amplifier) ​​module Of Intellijel uVCA 2 is. The patch cable has a flat underneath, and I think of this as the synth sound outlet that connects to the mixer and speakers. Here is a video that uses these two to produce sound.

Oscillator module

In this patching, the patch cable goes from the upper left jack of the oscillator STO to the middle left jack of the uVCA. And there's a sound coming out of the bottom left jack of the uVCA. When the oscillator hears the output from that unit,The same sound keeps coming out, and the sound doesn't stop.The output continuous sound is taken out and input to uVCA.

VCA module

uVCA is an amplifier (VCA). The input voice can be amplified or narrowed down to 0. uVCA has two channels of VCA, that is, two independent amplifiers (CH A / CH B) are built in, and CH A is used in the above patching. The small knob on top of uVCA is the CHA VCA volume knob (bias knob).

By the way, if you leave this setup alone, the volume of the continuous popping sound from the oscillator changes through the VCA,Just keep going outIt will be a system like this.

So, while messing around with the knobs and thinking about whether you can produce a melody, for example, you can mute the pitch (pitch) knob of the oscillator on the oscillator, or muzzle the volume knob of the VCA to start or stop the sound. I can only do it. So, using something like a sequencer or keyboard to generate the "control voltage",Make the flow of electricity do the same thing as moving the volume knob of the VCA or the pitch knob of the oscillatorLet's patch.

First of all, let's make the volume change more musical, without worrying about the oscillator pitch being constant. Add one module for control to the rack.

Patch 2

A patch that controls the amplifier volume with a PP touch plate

Yes, suddenly a black mysterious module came out. This is Make Noise's Pressure Points (PP) controller module. This controllerBy patching, you can use it a little like a keyboard.First, here is the voltage output from the jack on the upper right of the PPCV inI just typed into the jack. What is PP doing? Let's see a video using these three modules.

GATE SIGNAL

Actually, this module called Pressure Points has four touch plates made of copper wire as shown in the image, and when you press the touch plate"Gate signal"This type of control voltage is output from the upper right cable.

The "gate signal" is a voltage signal (red) that looks something like this, of course.One of the control voltageis. In detail, it is written separately as "GATE / CV", but it is only one of the voltage (CV) for controlling GATE.

Gate signal

In this way, the gate signal is a signal that jumps to a certain high voltage momentarily and returns to 0 in an instant when returning. By applying the above patch, the voltage that indicates "ON" is output from the cable only while the touch plate is being pressed."On and off"It seems that it can be used as a voltage signal that expresses (one of the basic uses of the gate signal).

CV in

The gate signal is going from PP to the uVCA "CV A" jack. This "CV A" is exactly what you will see modularly and frequently,Parameter controlled by voltageHere is an example of Jack to do.

For uVCA "CV A", CH AAmplifier volumeIt becomes a CV jack to control the. Also, if it is a filter, "CV in" is attached to control the voltage of its cutoff frequency. Also, as will be mentioned later, since the pitch of the oscillator is also controlled by the voltage to create a melody, the oscillator has "CV in" that controls the voltage of the pitch. The wave shaper also has a CV in that changes the shaping method, and with a delay, the delay time can be voltage controlled.

As you can see, modules often have some "CV in" so that they can be controlled by voltage, and how to patch and move them is also the basis of modular play. Also, what kind of CV in is attached will lead to the individuality of the module.

Now, the voltage signal in the CV in of uVCA is a gate signal that "rapidly rises and then suddenly falls". This gate signalBy using it as a CV of VCA, the volume of uVCA changes exactly as shown in the picture aboveWill do. In other words, the volume suddenly increased, the sound of the oscillator could be heard, and it could be set so that it would disappear suddenly when the GATE was turned off. You can now use it as a simple keyboard.

Attenuators

In CHA of uVCA, I haven't explained about the big white knob yet. This knob is called "Attenator" and comes in "CV in"Functions that adjust the strength of the voltageI will. Even though it is often non-modular, I think that there is a knob that adjusts the strength (amount) of applying the LFO and envelope, but that is equivalent to that. In the current case, it feels like adjusting the “height” of the GATE voltage.

Modules with "CV in" often have an attenuator for that CV, but in some cases they do not. In that case,Attenator moduleYou can make the same adjustment by inserting, etc. before CV in. The attenuator feels like air and is easy to forget, but it is an absolutely necessary function.

Patch 3

Add envelope module

Now, patch 2 can only express the rapid volume change represented by the gate signal. Therefore,A module that produces a voltage that can be used as a musical volume change based on this gate signalI put it between PP and uVCA. The video is below.

Envelope Generator module

The Make Noise Function is sandwiched between PP and uVCA. This is so-called"Envelope generator 'The module will generate an envelope voltage signal that can be specified by "Rise" and "Fall" at the timing of the incoming gate signal. Rise and Fall have the same meaning as attack and decay, respectively. And not the gate signal,Use the converted AD envelope voltage signal output from Function as CV of VCAIs the aim.

The photo below shows the gate signal (red) coming into the envelope module and the envelope (green) going out at the same time. Attack 0, sustain 100%, release Now the envelope setting is a little longer, so at the beginning it makes a sudden rise like tracing the gate signal, and the release after the last gate is turned off makes it possible to pass through Function. Instead of doing so, it will disappear while leaving a lingering finish. I put this green signal which is the output of Function into CV in of uVCA (In the video, I put a gate in Trig input of Function, but to sustain the envelope at a high position as shown in the picture, the left side of Trig input. Please input the gate to the signal input of.).

Gate signal (red) and envelope signal (green)

Now, the timing from when the sound is produced until it disappears and the volume control can be done quite smartly. With the patched modular above, there was no sound at first, and when I touched the PP touch plate, it sounded vigorously, and when I released the touch plate, I could hear the sound with a lingering finish.

Patch 4

Added patching to control the pitch (pitch) with PP

Next is pitch control. I mentioned above that the oscillator module has a "CV in" that allows you to voltage control its pitch, but this is usually the oscillator"1V / Oct"is what it reads. This time, I did not add a module, but added a patch cable from PP to STO. Here is the video.

CV control of oscillator pitch

As a function other than outputting the gate of PP, you can press one touch plate to output the voltage signal indicated by the three knobs above it from the jack on the right side of each knob.

Out of the three, take out the voltage signal of the top knob (the bottom one is used in the video) and set the oscillator"1V / Oct" (1 volt per octave)I am sticking to the input. This "1V / Oct" input is a CV in jack for controlling the STO pitch with voltage. 1V / OctWhen the voltage increases by 1 volt, the pitch increases by 1 octave.

By performing such patching, when you press the PP keyboard

• The gate signal is output, and the uVCA amplifier volume is controlled by the voltage signal converted by Function (made up to patch 3).
• Control the pitch of the STO with a voltage signal according to the knob on the touch plate you pressed (now you can do it with patch 4)

I will do two controls at the same time. The pitch is determined by which touch plate is pressed, and the length of the sound is determined by the length of the touch,"Like a keyboard"You have patched. PP has only 4 keys, but you can assign any pitch you like, and in fact you can chain as many as you like.

However, the voltage of the pitch is justIt is rarely a pitch of 12 scales.The pitch CV of the oscillator is set to 1 octave higher at 1V, and I don't know if the input voltage is just 12 notes above.

Therefore, insert the "quantizer module" so that the specified pitch voltage from PP is exactly 12 scales.

Patch 5

Quantizer added so that the pitch will be the specified scale

Quantizer module

The module installed on the far right is the quantizer module, Intellijel uScale. The Quantizer module"Put" the input pitch control voltage to the pitch voltage just above the scaleIt is a module that will give you.

Now, of the voltage output from the PP, the voltage used to specify the pitch becomes the voltage corresponding to exactly 1 scales by passing through uScale once (though the pitch knob also needs to be adjusted). From now, only the sound that feels the scale comes out. with this,Two CVs for pitch CV and gate are output from PPYou can now play 12 scales with envelopes.

CV ⇔ audio

So far, I have explained that the sound is controlled by voltage while performing concrete patching. In the above example, we used a CV to control both the gate and the pitch, and used the Pressure Points controller module for that control.

If you look at patch 5 again,There are two types of voltage through the cableI see that there is. Mainly the three modules on the right side were in and outControl signalAnd finally their control voltage goes through the two modules on the leftAudio signalI was controlling the movement of the car through the oscillator and VCA. The way to connect audio signals is very simple, and I think it takes some getting used to connecting control signals.

The control module and audio module are as follows.

• Control system:
  Envelope generator, LFO, CV sequencer, Attenuator, Quantizer, Through limiter, Etc ...
• Audio system:
  Analog oscillator,Digital oscillator, Noise generator, Wave Shaper, Filter, VCA, mixer, Etc ...

Some modules have individual functions, and some have a combination of functions. For example, a common envelope module is one that allows you to repeat an envelope into an LFO.

Now, I tried to classify the functions as above, but neither the control signal nor the audio signalWe are in the same ring in terms of handling voltage.And this is one of the interesting points of the modular, but as long as it is the same voltage,Audio signal as control signalYou can also use it.

For example, the output of the Oscillator module is an audio signal, but you can also use it to control, for example, the cutoff frequency of a filter or the pitch of another oscillator, creating a complex, metallic or dirty harmonic overtone structure. Can produce sound (FM). Also, if you gradually lower the pitch of the oscillator, the frequency will become lower than the audible range,As an LFOThere are also many oscillator modules that you can use.

さ ら に,Mixer and VCAAbout in the modular worldUsed for CV processing as much as audio processing. In other words, the mixer module can often mix multiple CVs (that is, voltage addition), and by allowing VCA to perform CV processing,CV can be controlled by CVIt looks like If you use the functions around here, you will be able to create quite interesting sound movements, and one of the merits of the modular is that you can do this physically and intuitively.

Anything

After this, if you power up the synth a little more, I think the next step would be to insert a filter module between the VCA and the oscillator. But the Eurorack modular world is literally anything. There are various other module options.

WEST COAST SYNTHESIS

In the world of modular synths, there are many wonderful modules that have not only filters, but also wave shapers and low pass gates, which have timbre shaping functions that are hard to find in non-modular synths.

The method of creating tones using modules such as the wave shaper and low pass gate is the synthesis method that has been adopted in the 1960s for the synth called Buchla. Since Buchla was made in San Francisco, it is often called the “West Coast Synth” as a historical category. If filter-based synths (“East Coast Style”) are based on simple controls on cutoff and resonance, West Coast Style will control the tone through more parameters. Therefore, unlike the keyboard, it works well with a module that can control a lot of sounds with one finger like the Pressure Points mentioned earlier, and it can also perform very complex tone synthesis.

DIGITAL MODULES

So far, I've returned to basics and talked about synths mainly in analog fashion. But the Eurorack modular world is not just analog. There are many digital modules that are easy to use and can do things that analog cannot do.

Digital oscillatorIs quite substantial in the Eurorack world and is well worth considering. There are many voice modules that go beyond the scope of oscillators, such as a wavetable oscillator that has waveform data in advance and creates a tone by sweeping it, an oscillator that can output chords, and an oscillator that can bit-crash. AlsoSampler moduleThere are also.

In the world of Eurorack modules, developers and engineers around the world design and sell various modules in a personal laboratory with the feeling that there is nothing like this. Each maker has its own personality, and they can be mixed and used. Of course, I think it's good to unify with brands that have a worldview.