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Using CV and Gate

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(extract from Oberkorn manual)

CVs and Gates – What are They?

This is not a complete beginner’s guide to analogue synthesizers, but here is a very brief explanation.

A CV (control voltage) is a varying voltage that can be used to control a parameter of an analogue synth. Which parameter really depends on the synth. Most synth’s have at least a pitch CV input (usually just called CV), and a filter cut-off CV input. These I think are the two most important. But a good modular will provide CV inputs to control most parameters.

Gate (sometimes called trigger) is typically used to trigger an envelope generator (which controls the synth’s volume, filter cut-off, and other parameters). Gate can be used to turn digital switches on and off, or to clock other analogue sequencers.

The beauty of analogue synth’s and modulars is that there are no rules. So you can use the CV and Gates how you want. If your synth has a voltage control input socket, then you can use it. That’s not to say any patch will sound good. Some won’t sound good or even work at all. So in those cases you’ll need to try something else. That’s the nature of modular synths.

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Step Sequencer Facts

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(extract from Oberkorn manual)

What is an analogue sequencer?

My definition of an analogue sequencer (since others may slightly disagree) is a device that will sequentially output a series of varying voltages (CVs) and gate conditions over time.

Sequencers (and when I use this word I will always be referring to analogue ones unless I state otherwise) will typically be 8-16 steps.

The Oberkorn has 16 steps.

To be a true analogue sequencer the output voltage must be unquantised, otherwise it’s digital! Digital means discrete steps. Oberkorn’s CV outputs can be swept smoothly from zero to full output level.

At each step you can change the voltage at the output socket and set whether a trigger / gate pulse is sent out.

Each step therefore has a potentiometer to change the voltage and a switch to change gate status.

As the clock runs the sequencer sequentially through each step (usually from one to 16), the state of the pot’s and switches is output at the sockets.

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Envelope Generators

IMG_4815The EG produces a CV that varies over a period of time. It’s start is triggered by a Gate or Trigger signal.

The main use for an EG is to vary the volume of a sound, (when used to control a VCA), to reproduce the way natural instruments sound. E.g. a piano sound starting loud when the key is struck, then gradually dieing away. It can also be used to change the timbre of a sound over time, by controlling the cut-off frequency of a VCF.

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The LFO Explained

IMG_4816The LFO gives a control voltage in the shape of a waveform. It is basically an oscillator which generates a cyclic waveform at low frequencies below the audio range.
The LFO can produce different wave-shapes used to modulate various other modules. Common uses of LFO modulation are to obtain vibrator (by modulating the pitch of a VCO), wah-wah (by modulating the filter cut-off frequency), tremolo (by modulating the gain of a VCA).

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