[PD] Re: [PD-announce] PWM in Pd

Frank Barknecht fbar at footils.org
Thu May 25 19:19:16 CEST 2006

Hans-Christoph Steiner hat gesagt: // Hans-Christoph Steiner wrote:

> I should say, I forgot that PWM was used in synthesis some, so I was  
> thinking about electronics and control when I was talking about PWM.   
> That's why my PWM objects are tailored towards, but should work fine  
> in the audio context too, unless you need the wandering DC offset.

The DC wanderer is not needed, but according to: 
it generally is considered to be like this:

  Note that Figure 3 shows a low-frequency amplitude modulation at the
  LFO speed (hence the downward and upward slope to the resulting PWM
  wave). Don't worry about this; the prominence of the modulation in
  the diagram is a consequence of the limited space available for the
  drawing. If the audio waves are pitched at a few hundred Hertz
  (somewhere in the middle of the piano keyboard) and modulated by an
  LFO running at a fraction of a Hertz, this modulation is of no
  significance, provided that you allow sufficient headroom to
  accommodate it. If you want, you can use a high-pass filter to
  remove it, but it's rarely worth the effort.

Aliasing/foldover is a much bigger concern with this naive kind of
PWM/rectangle wave generation in Pd.

 Frank Barknecht                 _ ______footils.org_ __goto10.org__

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