[LAD] (Modular) Synth and Clipping

Tim Goetze tim at quitte.de
Sun Jun 16 10:55:37 UTC 2013

Hi Aurélien,

>- What method of clipping is used will give a "personality" to the
>module: hard clipping, soft clipping, the method used for soft
>clipping, etc...right?

from my experience, there are two main factors determining the
character of waveshaping distortion: one is the hardness of the
clipping transition, the other its +/- symmetry.

A perfectly symmetric clipping function will generate only odd-order
harmonics.  Breaking the symmetry gives rise to even-order harmonics,
easily achieved for example through the simple addition of a DC offset
before clipping.  At high gain, the degree of symmetry of the clipping
function becomes much more important to the "personality" of the sound
than the softness of the clipping transition.

>- Soft clipping will deform any waves of amplitude -1/1 even if it
>doesn't exceed the accepted threshold, because just before reaching
>the threshold  the algorithm will take over and softly make the signal
>reach the maximum amplitude and keep it there until the original
>signal goes back under a set threshold.....right?

You should also consider asymptotic functions, atan for example, that
can be used for clipping with a 'soft' ceiling, never reaching total
saturation.  I prefer their sound, but the difference can be subtle.

>- Is there a preferred stage for clipping? In the case of a filter,
>should we clip before filtering, after or both? Or are all these
>options valid and that's what will give an additional personality to
>the filter?

The heart of many distortion pedals is a clip|filter|clip chain, but
there are so many ways to vary or extend the scheme.  For example, an
interesting approach to digital ladder filters wedges saturation
circuitry between the filter stages.

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