CV,Gate & Synthesis.This page is on the basic background knowledge, of CV/Gate & Synthesis. CV/Gate CV/Gate stand for, Control Voltage/Gate which was a used method, of controlling Synthesizers & Drum Machines with Sequencers before MIDI control was invented. Please note to use an old style analogue synth with MIDI, you have to get a MIDI-to-CV converter unit. Recent analogue synths, such as the Novation BassStation Rack, feature built-in MIDI-to-CV convertors as well. However, new technology analogue synths are back. From the original manufactures who made them first and new manufactures coming through. With lots of knobs, buttons and sliders to play with. Control Voltage/gate is made up of two parts • The CV, corresponded what note was played & is a control voltage corresponding to the pitch. • The Gate, corresponded when a key was pressed and released. It was a voltage that remained high while the key was still held. Note the Gate is sometimes called the Trigger.
Variations on the CV/Gate interface were used, the standard was by Roland Corporation. Roland CV was a voltage signal of 1v/octave, with another volt for raising the signal pitch an octave more. The Roland Gate is a positive going signal, called a Voltage Trigger or v-trigger. Which is usually a low signal, and then goes high as long as the note is held down. Roland synths such as the SH line, the TB-303, and the MC-202 and MC-4 all used this standard. Moog, Korg and Yamaha synths, used a negative trigger signal called a Short Circuit Trigger or s-trigger. Which is usually keeping a voltage high, shorting the trigger circuit whenever the note is played.
Korg analogues used 1v/octave CV and has a gate switchable between v-trigger and s-trigger. Both Sequential Circuits and Arp also followed this standard.
Moog synths used 1v/octave CV, & used s-trigger gate. Instead of using a typical 1/4" or 1/8" jacks, Moog used a different connector for CV/gate. Now you see why all the manufactures got together, to come up with one MIDI Standards.
• Hertz per volt a Yamaha Implementation.
Basic Sound Synthesis Basic sound synthesis, contains Waveforms of sound, or electrical signal with time. And Harmonics are, a high frequency of a complex waveform. • Sine Wave, contains a pure tone with no harmonics. Like a 1KHz test tone frequency. • Square Wave, contains a series of odd harmonics.
• Sawtooth Wave, contains only even harmonics. • Triangle Wave, contains only odd harmonics, with lower harmonics than the square wave.
These are the graphic basic waveform, drawings down below. Their are more complex waveforms, but they are a mixture of the above. Plus an 20hz to 20khz pure tone Sinewave, Squarewave, Sawtoothwave and Trianglewave audio, please turn down your volume on this one. Some speakers may not be able to produce some frequencies but some can. CAUTION HIGH FREQUENCIES! keep your pets away from the speakers, enjoy!
Sinewave 20Hzto20KHz
Squarewave 20Hzto20KHz
Sawtoothwave 20Hzto20KHz
Trianglewave 20Hzto20KHz
The Oscillator, is the part of the synth. Which generates the periodic waveform. The PWM, is the Pulse Width Modulation. Which is the term for Modulating of the Duty Cycle Pulse Wave. This can alter the Timbre tonal colour of the sound being used. The LFO modulation pulse width, can produce a false chorus effect sound. The LFO, is the Low Frequency Oscillator. Which uses a modulation source, below human hearing, around about 20Hz. LFO waveshape is a sine wave, but you can choose Square, Sawtooth and Triangle as well. The VCO+VCA, is the Voltage Controlled Oscillator and Amplifier, Plus the VCF, is the Voltage Controlled Filter. Are all part of the process, of controlling the speed, volume and sound of the waveform. The ADSR, is the Envelope Generator. Which features Attack, Decay, Sustain and Release. In the ADSR part of the synth. • The Attack phase of the sound, reaches maximum volume. Like drums have fast attack and string have a slow upward attack. • The Decay phase of the sound level drops in time. • The Sustain phase of the sound level will settle if the key is held down. • The Release phase of the sound level reduces, after the key has been released.
Basic Synthesis on Reason Subtractor Synth, enjoy!
Retrosound Analogue Synths
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