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