2010/9/12 <pd-list-request@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@artengine.ca>
To: Pierre Massat <pimassat@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@artengine.ca>
To: Pierre Massat <pimassat@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.or.at>
To: "João Pais" <jmmmpais@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@sympatico.ca>
To: Mathieu Bouchard <matju@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.or.at>
To: "João Pais" <jmmmpais@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@artengine.ca>
To: Martin Peach <martin.peach@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@anechoicmedia.com>
To: pd-list@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

---------- Messaggio inoltrato ----------
From: Martin Peach <martin.peach@sympatico.ca>
To: Mathieu Bouchard <matju@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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