synthesizer

[11ivan11]

Hi, how to make knob that changes oscillator wave-form?

[utdgrant]

Hi, how to make knob that changes oscillator wave-form?

It depends on whether you want to smoothly morph between waveforms, or use the knob as a rotary selector switch.

Are you thinking along the lines of the RSF Kobol, with its continuously variable morph knob?

KnobSmoothWaveform.jpg (11.33 KiB) Viewed 1160 times

Or a Minimoog with a discrete selection of switched waveforms?

KnobSwitchedWaveform.jpg (14.81 KiB) Viewed 1160 times

[Waverley Instruments]

Or you could get real fancy...

[resoluxe]

Now that is fancy - love it!

[11ivan11]

like Minimoog with a discrete selection of switched waveforms

[utdgrant]

like Minimoog with a discrete selection of switched waveforms

Firstly, select the style of knob you would like from the selection available in VMD.

Decide how many different waveforms you want to switch between. Make this a constant called NUMBER_OF_WAVEFORMS.

In the knob parameters, set min range to 1.0 and max range to NUMBER_OF_WAVEFORMS. Set the number of discrete steps to NUMBER_OF_WAVEFORMS.

Try this out in the debugger to get a feel for how this looks and feels.

If you want to read some similar code, download the Dome Music Technologies source code zip file, and open up one of the Drawbar Mixer projects. This turns a VoltageSlider control into a 9-position (0 for off and volumes 1 to 8) vertical switch.

[utdgrant]

like Minimoog with a discrete selection of switched waveforms

If you want an example of how to generate switched waveforms in ProcessSample, you can check out the source code for the Pink Flight Divide-Down Oscillator. This has a three-position switch to choose between Sawtooth, Pulse and Triangle waveforms, but you can just as easily use a knob with discrete steps as described in my previous post.

PinkFlightWaveSwitch.PNG (94.95 KiB) Viewed 543 times

The wave selection and generation logic is contained in these lines of code:

Code: Select all

         switch (currentWaveform)
         {
            case PULSE:
            {
               channelOscillator[i].SetPulseWidth(pulseWidth);
               oscillatorOutput = channelOscillator[i].GetPulseValue();
            }
            break;
            
            case TRIANGLE:
            {
               oscillatorOutput = channelOscillator[i].GetTriangleValue();
            }
            break;
            
            default:
            {
               oscillatorOutput = channelOscillator[i].GetSawtoothValue();
            }
            break;
            
         }
         

[utdgrant]

I threw this one together in about an hour tonight. It's not the clearest of code, or the most efficient, but it gets the job done.

SwitchedAnalogueOscillator.jpg (26.35 KiB) Viewed 498 times

YouTube Demo: Basic Switched Waveform Analogue Oscillator for Voltage Modular

The waveform selector knob is limited to four discrete steps.

WaveformKnob.jpg (72.17 KiB) Viewed 498 times

This is the User Variable code:

Code: Select all

// Add your own variables and functions here

private final float BASE_FREQUENCY = 65.4f;
private float previousPitchIn;
private AnalogOscillator mainOscillator = new AnalogOscillator();

This is the initialisation code:

Code: Select all

public void Initialize()
{
   // add your own code here

   previousPitchIn = -1000.0f;   // Force recalculate on first ProcessSample

This is the ProcessSample code:

Code: Select all

public void ProcessSample()
{
   // add your own code here

   float tempFloat;
   float pitchIn;
   
   double tempDouble;
   double pulseWidthIn;
   double pulseWidth;
   double outputValue;
   
   int waveformNumber;
   
   pitchIn = (float) inputJackPitch.GetValue();
   if (pitchIn != previousPitchIn)
   {
      // Recalculate exponential frequency
      tempFloat = BASE_FREQUENCY * Values.FastTwoToTheX(pitchIn);
      mainOscillator.SetFrequency(tempFloat);
   }
   
   waveformNumber = (int) knobWaveform.GetValue();
   
   if (waveformNumber == 2)   // Pulse
   {
      pulseWidth = knobPulseWidth.GetValue();
      if (inputJackPWM.IsConnected())
      {
         tempDouble = inputJackPWM.GetValue() *
                      knobPWM.GetValue() *
                      0.2;
         pulseWidth += tempDouble;
      }
      mainOscillator.SetPulseWidth (pulseWidth);
   }
   
   mainOscillator.AdvanceSample();
   
   switch (waveformNumber)
   {
      case 1:
      {
         outputValue = mainOscillator.GetSawtoothValue();
      }
      break;
      
      case 2:
      {
         outputValue = mainOscillator.GetPulseValue();
      }
      break;
      
      case 3:
      {
         outputValue = mainOscillator.GetTriangleValue();
      }
      break;
      
      default:
      {
         outputValue = mainOscillator.GetPureSineValue();
      }
      break;
      
   }
   
   outputJack.SetValue(outputValue);
   
}

[11ivan11]

thank you but, my oscillators will go through mixer, that mixes signals as in korg ms-20

[utdgrant]

thank you but, my oscillators will go through mixer, that mixes signals as in korg ms-20

That's simple.

Add a new knob for output level.

VCOOutputLevelKnob.jpg (70.45 KiB) Viewed 441 times

YouTube demo: Adding Level Knob to Switched Oscillator

Add a SmoothValue object to the User Variables area:

Code: Select all

private final float BASE_FREQUENCY = 65.4f;
private float previousPitchIn;
private AnalogOscillator mainOscillator = new AnalogOscillator();

private SmoothValue smoothVolume = new SmoothValue();  // NEW LINE ***

Add these lines to the Knob_Changed event in Notify():

Code: Select all

      case Knob_Changed:   // doubleValue is the new VoltageKnob value
      {
         if (component == knobOutputLevel)
         {
            smoothVolume.SetValue(doubleValue);
         }
      }
      break;

Add this line to Initialize():

Code: Select all

   previousPitchIn = -1000.0f;   // Force recalculate on first ProcessSample
   smoothVolume.SetValue(knobOutputLevel.GetValue());    // NEW LINE***

Add this line to ProcessSample():

Code: Select all

      default:
      {
         outputValue = mainOscillator.GetPureSineValue();
      }
      break;
      
   }
   
   outputValue *= smoothVolume.GetSmoothValue();    // NEW LINE ***
   
   outputJack.SetValue(outputValue);
   

And you're good to go.