[PD] help with oscillator modulation

Carl S larstocqueville at gmail.com
Mon Oct 1 23:50:19 CEST 2018


Nice! if you later decide to use portamento or pitch modulation of the
carrier osc, you can always replace the clip~ object with max~  and send
the signal version of the carrier frequency to one side, and the modulation
to the other. this will act identically as it will either send mod values
higher than the carrier or the straight carrier.

I could be wrong, but I think the bob~ object has a clipping/saturating
component that is more elegant and less likely to alias than a straight
clip~. is this true? I think it can also accept startup messages to specify
oversampling for better performance in this way. I think you could scale
input to bob~ even to clip at the carrier frequency. But it would be nice
to know if bob~ is actually good for this job before patching it up.

I am worried about the aliasing you will get with more complex waveforms
than sine. I am interested in some methods like polyBLEP to smooth out
discontinuities and wonder if they could be used downstream from an audio
rate modulated oscillator and still function correctly. I've avoided this
in my own oscillators by doing silly and expensive things with short delay
lines. I'll forward my findings if i make any headway on this.

it's totally my pleasure to mess around with oscillator/synth component
stuff in pure data! But beware my advice because my stuff is pretty
scrappy.


On Mon, Oct 1, 2018 at 5:15 PM oliver <oliver at klingt.org> wrote:

> Carl S wrote:
> > A couple problems with the patch I posted. Any of the bob~ objects need
> > the message [saturation 1( sent to them to function the way I intended.
> >
> > Also, turns out I was totally wrong about the through zero concept- you
> > need to clip the frequency input of the modulated osc at 0Hz. Attached
> > is a patch that demonstrates this. one of the examples shows use of bob~
> > to restrict values
>
> hi, carl !
>
> first, thank you very very much for your kind help. all of your
> suggestions are interesting to study and all have a distinct modulation
> "flavour". i have to confess that i don't fully understand the [bob~]
> approach, but the rectifying example was very clear.
>
> after a little tweaking i came to a solution that sounded the closest to
> the effect i was looking for. the difference in my approach is to clip
> the frequency input of the modulated osc not at 0 Hz but at the carrier
> frequency.
>
> example attached
>
> thanks again for your examples !
>
> best
>
> oliver
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