[PD] Pd-list Digest, Vol 66, Issue 57

[Mathieu Bosi]

Maybe also this could be of interest:

 http://puredata.hurleur.com/sujet-2453-cubic-soft-clip-distortion

Mathieu

2010/9/12 <pd-list-request at iem.at>

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> Today's Topics:
>
>   1. Re: Guitar distortion (Chebyshev?) (Mathieu Bouchard)
>   2. Re: Guitar distortion (Chebyshev?) (Mathieu Bouchard)
>   3. Re: puredata.info wiki structured text format?
>      (Hans-Christoph Steiner)
>   4. Re: Guitar distortion (Chebyshev?) (Martin Peach)
>   5. Re: Pd-extended 0.42.5 release candidate 6 released!
>      (Hans-Christoph Steiner)
>   6. Re: Guitar distortion (Chebyshev?) (Mathieu Bouchard)
>   7. Re: Guitar distortion (Chebyshev?) (Kim Cascone)
>   8. Re: Guitar distortion (Chebyshev?) (Martin Peach)
>
>
> ---------- Messaggio inoltrato ----------
> From: Mathieu Bouchard <matju at artengine.ca>
> To: Pierre Massat <pimassat at gmail.com>
> Date: Sun, 12 Sep 2010 11:07:29 -0400 (EDT)
> Subject: Re: [PD] Guitar distortion (Chebyshev?)
> On Sun, 12 Sep 2010, Pierre Massat wrote:
>
>  One issue is that it seems to sound good only when the amplitude of the
>> sound is close to 1, which is obviously not the case for a raw guitar sound.
>>
>
> Tu peux utiliser la version polynômiale des formules de Tchébycheff, car
> celles-ci s'étendent au delà de 1 sans problème, tandis que la version
> arccosinus a des problèmes en dehors de l'intervalle -1..+1 (pour simplifier
> les choses, on dit habituellement qu'elle n'existe pas en dehors de cet
> intervalle...).
>
> Mais c'est quand même mieux de pas tellement dépasser ±1, c'est juste que
> les polynômes pardonnent beaucoup plus. C'est un effet très dépendant du
> volume.
>
>  _______________________________________________________________________
> | Mathieu Bouchard ------------------------------ Villeray, Montréal, QC
>
> ---------- Messaggio inoltrato ----------
> From: Mathieu Bouchard <matju at artengine.ca>
> To: Pierre Massat <pimassat at gmail.com>
> Date: Sun, 12 Sep 2010 11:13:55 -0400 (EDT)
> Subject: Re: [PD] Guitar distortion (Chebyshev?)
> On Sun, 12 Sep 2010, Pierre Massat wrote:
>
>  I m not trying to model an amp here, i m only interested in modeling a
>> distortion unit.
>>
>
> Ah, I forgot, did you try [expr~ tanh($v1)] ?
>
> At first I assumed that you wanted to go beyond that simple distorsion and
> into more interesting forms of distortion. Chebyshev's are only useful if
> you want something that can also sounds like pitch shifts by harmonic steps.
>
> I think that tanh is rather close to the physical behaviour of capacitors
> being strained, but surely not exactly that, and I didn't do the math to
> figure out what the real formula would be. (Did anyone try that ?)
>
>  _______________________________________________________________________
> | Mathieu Bouchard ------------------------------ Villeray, Montréal, QC
>
> ---------- Messaggio inoltrato ----------
> From: Hans-Christoph Steiner <hans at at.or.at>
> To: "João Pais" <jmmmpais at googlemail.com>
> Date: Sun, 12 Sep 2010 11:29:51 -0400
> Subject: Re: [PD] puredata.info wiki structured text format?
>
> On Sep 12, 2010, at 4:14 AM, João Pais wrote:
>
>  I personally loathe the stucturedText format.  I find it very difficult
>>> to make it work.  I use the MoinMoin syntax whenever I create a page on
>>> puredata.info.
>>>
>>
>> is there a reference link for that as well?
>>
>> I didn't said, but I'm asking this because I wanted to put in an excel
>> chart. usually I use normal html.
>>
>
>
> http://wiki.winehq.org/SyntaxReference
>
> .hc
>
>
>
> ----------------------------------------------------------------------------
>
> Terrorism is not an enemy.  It cannot be defeated.  It's a tactic.  It's
> about as sensible to say we declare war on night attacks and expect we're
> going to win that war.  We're not going to win the war on terrorism.
>  - retired U.S. Army general, William Odom
>
>
>
>
>
>
> ---------- Messaggio inoltrato ----------
> From: Martin Peach <martin.peach at sympatico.ca>
> To: Mathieu Bouchard <matju at artengine.ca>
> Date: Sun, 12 Sep 2010 11:32:41 -0400
> Subject: Re: [PD] Guitar distortion (Chebyshev?)
> On 2010-09-12 11:13, Mathieu Bouchard wrote:
>
>> On Sun, 12 Sep 2010, Pierre Massat wrote:
>>
>>  I m not trying to model an amp here, i m only interested in modeling a
>>> distortion unit.
>>>
>>
>> Ah, I forgot, did you try [expr~ tanh($v1)] ?
>>
>> At first I assumed that you wanted to go beyond that simple distorsion
>> and into more interesting forms of distortion. Chebyshev's are only
>> useful if you want something that can also sounds like pitch shifts by
>> harmonic steps.
>>
>> I think that tanh is rather close to the physical behaviour of
>> capacitors being strained, but surely not exactly that, and I didn't do
>> the math to figure out what the real formula would be. (Did anyone try
>> that ?)
>>
>>
> See attached patch. I use it instead of a fuzz box now.
> It's not the capacitors, it's the amplifier losing gain when it approaches
> the power supply. Vacuum tubes have a softer knee than transistors.
>
>
> Martin
>
>
> ---------- Messaggio inoltrato ----------
> From: Hans-Christoph Steiner <hans at at.or.at>
> To: "João Pais" <jmmmpais at googlemail.com>
> Date: Sun, 12 Sep 2010 12:03:25 -0400
> Subject: Re: [PD] Pd-extended 0.42.5 release candidate 6 released!
>
> On Sep 12, 2010, at 4:14 AM, João Pais wrote:
>
>  a couple of my abstractions aren't packaged with this distribution, e.g.
>>>> bezier.pd (it's in
>>>>
>>>> https://pure-data.svn.sourceforge.net/svnroot/pure-data/trunk/abstractions/jmmmp/
>>>> ).
>>>>
>>>
>>> Yes, once the release process has started, then Pd-extended is built out
>>> of a branch in SVN and not trunk.  You can either check in the changes
>>> yourself, or tell me what to check in.
>>>
>>
>> you mean there are 2 places where we should submit the code? is there a
>> wiki page with the instructions for it?
>>
>
> When making a release, we work out of a branch so that only expected
> changes get incorporated into the release.
>
>  I would prefer to do it myself, then I don't have to ask you again next
>> time about it :)
>>
>> João
>>
>
> The current Pd-extended release branch is here:
>
> svn co
> https://pure-data.svn.sourceforge.net/svnroot/pure-data/branches/pd-extended/0.42
>
> There are some basic instructions here, basically you want to do an SVN
> merge from trunk into a branch:
>
> http://puredata.info/docs/developer/GettingIntoPdextended
>
> some instructions:
>
> http://www.google.com/webhp?hl=en#sclient=psy&hl=en&site=webhp&q=svn+merge+trunk+into+branch&aq=f&aqi=g-c1g-o1&aql=&oq=&gs_rfai=&pbx=1&fp=ab5cdb1806fef4aa
>
> .hc
>
>
> ----------------------------------------------------------------------------
>
> Programs should be written for people to read, and only incidentally for
> machines to execute.
>  - from Structure and Interpretation of Computer Programs
>
>
>
>
>
> ---------- Messaggio inoltrato ----------
> From: Mathieu Bouchard <matju at artengine.ca>
> To: Martin Peach <martin.peach at sympatico.ca>
> Date: Sun, 12 Sep 2010 12:05:30 -0400 (EDT)
> Subject: Re: [PD] Guitar distortion (Chebyshev?)
> On Sun, 12 Sep 2010, Martin Peach wrote:
>
>  It's not the capacitors, it's the amplifier losing gain when it approaches
>> the power supply.
>>
>
> Yeah, but it seems to be a pattern similar to the one found in capacitors,
> because capacitor theory has exp(-x) all over it, and the only way that
> capacitors behave like [hip~] is when the signal is much below the capacity
> rating (µF)... otherwise they lose gain... when they don't, it's because
> exp(-x) can be well approximated by x.
>
> And then, exp is very close to tanh in several different ways, one of them
> being this (use gnuplot) :
>
>  plot [-2:2] [-1:1] exp(x*sqrt(2))-1, 1-exp(-x*sqrt(2)), tanh(x), x
>
> I put the plain 'x' at the end to show what I mean above (though you
> already know that)
>
>  _______________________________________________________________________
> | Mathieu Bouchard ------------------------------ Villeray, Montréal, QC
>
> ---------- Messaggio inoltrato ----------
> From: Kim Cascone <kim at anechoicmedia.com>
> To: pd-list at iem.at
> Date: Sun, 12 Sep 2010 10:22:59 -0700
> Subject: Re: [PD] Guitar distortion (Chebyshev?)
> couldn't locate the Smeck.pd download on the link posted for Miller's page
> but here is the direct link in case you couldn't find it:
> http://crca.ucsd.edu/~msp/smeck/latest/smeck-01.zip<http://crca.ucsd.edu/%7Emsp/smeck/latest/smeck-01.zip>
>
>
>
>
> ---------- Messaggio inoltrato ----------
> From: Martin Peach <martin.peach at sympatico.ca>
> To: Mathieu Bouchard <matju at artengine.ca>
> Date: Sun, 12 Sep 2010 13:24:57 -0400
> Subject: Re: [PD] Guitar distortion (Chebyshev?)
> On 2010-09-12 12:05, Mathieu Bouchard wrote:
>
>> On Sun, 12 Sep 2010, Martin Peach wrote:
>>
>>  It's not the capacitors, it's the amplifier losing gain when it
>>> approaches the power supply.
>>>
>>
>> Yeah, but it seems to be a pattern similar to the one found in
>> capacitors, because capacitor theory has exp(-x) all over it, and the
>> only way that capacitors behave like [hip~] is when the signal is much
>> below the capacity rating (µF)... otherwise they lose gain... when they
>> don't, it's because exp(-x) can be well approximated by x.
>>
>>
> I guess it's similar since capacitors charge at a rate proportional to a
> voltage difference, while transistors can supply charge carriers at a rate
> proportional to a voltage difference, so caps charge fastest when they are
> nearly empty and transistors have the best gain with small signal inputs.
>
> The whole universe has exp written all over it in fact...
>
>  And then, exp is very close to tanh in several different ways, one of
>> them being this (use gnuplot) :
>>
>> plot [-2:2] [-1:1] exp(x*sqrt(2))-1, 1-exp(-x*sqrt(2)), tanh(x), x
>>
>> I put the plain 'x' at the end to show what I mean above (though you
>> already know that)
>>
>>
> Of course, all the hyperbolic trig functions are made from exp, by
> definition.
>
> http://en.wikipedia.org/wiki/Hyperbolic_function
>
> Another use of exp is the sigmoid function used in biology, that can be
> used to make a soft transition from one state to another as in 'fuzzy
> logic'.
>
> Martin
>
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