SynthEdit is modeled after real Analog Synthesisers.
In a modular Synth the various modules offer many features and functions, there are no rules as to how you connect the modules (that's the fun!). As a result all modules must be compatible. This is achieved with Voltage Control. All modules respond to the same voltage range, in SynthEdit's case 10 Volts. Most module inputs have a useful range from 0.0 to 10.0.
The Oscillator pitch is calibrated in Volts per Octave. 5 Volts plays note 'Middle A' the note in the center of a piano keyboard. (also known as 440 cycles per second, or Hertz). If you increase the input by 1 Volt, the pitch goes up one octave ( the frequency doubles to 880 Hz )...
To convert a specific frequency to a voltage..
Frequency = 440 * 2 ^ (Volts - 5)
The amplifier works by default on a Decibel scale. A volume of 0 is silence, and 10 is full volume.
This shows that an input of 10 Volts produces full volume ( 0 Decibels ), and a
gain of 0 volts gives silence ( -70 decibels, very quiet).
You can choose 3 different resonse curves.
Exponential: This scale imitates the voltage drop of a discharging capacitor. Why?, many hardware synths generated their envelopes using this method, as it it similar to the decay curve of a natural sound.
What do they look like?, all these sounds have the same envelope settings, but different VCA modes...
Decibel mode VCA decay
Exponential mode
Linear mode VCA (or Level Adjust)
The ADSR envelope times are based on a 'TimeCent' scale. This is a similar concept to decibels, whereby you get finer control over the short envelope segments..
Time = 2 ^ (Volts - 6.666666)
Volts = log(Time)/log(2) + 6.66666
The shortest time shown here at 0 Volts is around 10 milliseconds. Sometimes you may need faster envelope times, e.g. for Drum sounds. You get shorter times by using negative voltages.