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What does pulse width do on non-square waveforms?

4

It took me a while to notice that the PW parameter is adjustable on all the built-in waveforms, not just pulse waves (square and analog square). Cranking it to 50 seems to result in the same waveform one octave higher, though I haven't analyzed it closely.

Is this documented anywhere, or can anyone explain its effect?

Best Answer

  • 2
    MafooMafoo Posts: 52
    Answer ✓

    Square behaves as expected, so I did not make a gif of that one. The sine, saw, and triangle all seem to approach an octave up.
    Saw:

    Sine:

    Tri:

Answers

  • 0
    esc746esc746 IrelandPosts: 12

    I don't own a Deluge but since no-one has answered, I will guess that it changes the duty cycle in other ways. For example, on a saw it might change the slope, or on a sine wave the asymmetry.

    I would hook up an oscilloscope and see!

  • 1
    MafooMafoo Posts: 52

    I'll check it out on a scope when I have some time this weekend.

  • 0
    amiga909amiga909 SwitzerlandPosts: 739

    interesting thread. never thought about the fact u can PW mod all oscillator waves (square, triangle, sine, saw).
    https://www.kvraudio.com/forum/viewtopic.php?t=441976 compares PWM on all waves to phase distortion synthesis. fast lfo on sinus PW gives me sounds that remind me of my Casio.

  • 0
    amiga909amiga909 SwitzerlandPosts: 739

    thanks for the gifs mafoo, would be a great addition to the online manual.
    i am not deep into dsp and such, what does it mean its one octave up? would u compare it to something other synths offer, maybe with a different term?

  • 1
    MafooMafoo Posts: 52
    edited August 4

    I am not super knowledgeable in the physics of the waves and all that, but it actually sounds like as you turn up the PW on each wave the pitch rises until you hit the next octave up, so the wave is repeating twice as often. Between 0 and 50 you get some Interesting harmonic changes because the wave is restarting before it completes a cycle, similar to what happens when you sync oscillators that have different pitches. The incomplete cycles tend to make for unusual harmonic series.

    I should also clarify, the gifs show me turning the PW up to 50 and then slowly back to 0. I think my oscilloscope is automatically adjusting itself to show two compete wave cycles, so right when it hits 50 and is actually an octave higher, the window automatically adjusts and you suddenly see 2 cycles again after seeing 4 cycles momentarily.

    Post edited by Mafoo on
  • 1
    duelinmarkersduelinmarkers Austin TX USPosts: 81

    @Mafoo said:
    similar to what happens when you sync oscillators that have different pitches.

    This looks to me like the best description. It seems to be equivalent to a 1-octave sweep up while hard synced to an oscillator at the base pitch.

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