[sdiy] Walsh Functions/EN S-008

Michael E Caloroso mec.forumreader at gmail.com
Sat Sep 16 01:37:46 CEST 2017


The alloys that transistors are made of come from nature, do they not?

MC

On Sep 14, 2017, at 2:58 PM, ijfritz at comcast.net wrote:

Well, neither are transistors.   :-)

On 9/15/17, Ian Fritz <ijfritz at comcast.net> wrote:
> Tom --
>
> Thanks for the discussion.  I can tell from your response that I haven't
> explained myself well enough. Here goes for another try.
>
> Multiple pulsed or stepped waveforms have different spectra and sounds
> from traditional waveforms.  (If you are happy with the MacMoog
> waveforms, then fine.) The new spectral features extend throughout the
> audio range.  The ones at the lower end give timbers that are
> fundamentally different from traditional ones.  The ones at high
> frequencies are strong, sure.  But ultimately they roll off at 6 dB /
> Oct, just like the traditional Saw and Pulse waveforms.  Obviously, you
> can use LP filtering to reduce the brightness, just as you might on the
> traditional waveforms. For some analytics on typical double-pulse
> waveforms, please refer to Bernie's EN #228, available online:
> http://electronotes.netfirms.com/free.htm
>
>  >>>
> What’s wrong with trying to transform a flute into a clarinet? One has
> hardly any harmonics, and the other has a few more, but neither have
> many. If you don’t like that example, pick one with less. It doesn’t
> matter. The point is only: why limit yourself to waveforms with a lot of
> harmonic content? Why is that better?
> <<<
>
> I think you may have  misunderstood what I was trying to say.  I asked
> why you would use a Walsh generator to morph between low harmonic
> content waveforms, when there are simpler methods available.  What
> simple methods, you ask? Well, dynamic mixing of the two waves is
> probably the easiest method, at least conceptually.  For your
> flute-clarinet question, you can  morph between Tri and Square waves by
> amplifying and clipping the Tri.  Morphing Tri to Saw is a bit trickier,
> but a few years back I figured out how to do this using a saturating
> negative impedance converter. A fairly detailed explanation, with
> representative sound clips, is on my website:
> http://ijfritz.byethost4.com/sy_cir10.htm
> I actually have dedicated versions of this circuit on two of my VCOs.
> The advantage of morphing vs mixing is there are no steps, so driving
> other waveshapers goes more smoothly.
>
>  >>>
> The more interesting stuff for me is the subtler changes in timbre that
> can be achieved, that give the ear interest but don’t “wow!” it with
> unusual gimmicks.
> <<<
>
> Actually, with a greater variety of waveform choices you have WAY MORE
> scope along these lines.  I did a lot of work years ago synthesizing
> quasi-realistic sounds.  I've never put all this up, but short
> representative clips are here:
> http://ijfritz.byethost4.com/sy_close.htm
> Almost all these sounds were generated using the Double Pulse Waveform
> Generator or the DoubleDeka 10-step VCO.  (At least if "the high quickly
> wears off and these are sounds that get tired fast", the clips are short.)
>
> There are many examples of sounds from pulse/step waveform sources on my
> website and you tube channel.
> http://ijfritz.byethost4.com/  website index
>   http://ijfritz.byethost4.com/sy_cir8.htm  5 Pulser Waveshaper Project
> http://ijfritz.byethost4.com/sy_cir5.htm  Double Pulse Waveform generator
> http://ijfritz.byethost4.com/sy_cir6.htm   Wavolver
> http://ijfritz.byethost4.com/sy_cir10.htm  SNICster
> http://ijfritz.byethost4.com/MiscProj/DD.htm  DoubleDeka
> https://www.youtube.com/user/frijitz001  Demos of commercialized modules
>
> There are also numerous comments and videos from other users of these
> modules on the electro-music and muff's forums and on you tube.  This
> post is already too long, so I won't elaborate on all these.
>
>  >>>
> For this reason I’ve been looking at the way shifting the phase of the
> harmonics in a waveform affects the crossfade between one waveform and
> another - suddenly something that was previously a simple linear
> crossfade becomes non-linear and more interesting, not in a ‘grab you by
> the ears and shake you” way but rather something more subtle. This for
> me is more where I’d like to be.
> <<<
>
> I have no idea what this means.  But by all means, please get back to us
> when you actually have something to show.
>
> Ian
>
>
> On 9/14/2017 5:45 PM, Tom Wiltshire wrote:
>> Hi Ian,
>>
>> Thanks for that report. It’s very interesting. “Smooth, even if fairly
>> extreme” is something I might need to hear to understand. Yes, I
>> understand that there will be a fairly strong fundamental in any waveform
>> like this - even if that’s mainly perceptual rather than actual. It’s
>> still what we hear. Morphing between two low-harmonic waveforms has all
>> kinds of uses. What’s wrong with trying to transform a flute into a
>> clarinet? One has hardly any harmonics, and the other has a few more, but
>> neither have many. If you don’t like that example, pick one with less. It
>> doesn’t matter. The point is only: why limit yourself to waveforms with a
>> lot of harmonic content? Why is that better?
>>
>> I don’t understand what you mean by "why would you do it this way instead
>> of by simple means?”. If it's important, please explain. I’m sorry I
>> didn’t get it first time.
>>
>> In many ways, I don’t think “extreme wave shaping” is my direction of
>> travel. Extreme results are very quickly perceived as artificial, and in
>> my view that makes them a “quick fix” - perhaps they’re exciting for a
>> moment, but the high quickly wears off and these are sounds that get tired
>> fast. The more interesting stuff for me is the subtler changes in timbre
>> that can be achieved, that give the ear interest but don’t “wow!” it with
>> unusual gimmicks. For this reason I’ve been looking at the way shifting
>> the phase of the harmonics in a waveform affects the crossfade between one
>> waveform and another - suddenly something that was previously a simple
>> linear crossfade becomes non-linear and more interesting, not in a ‘grab
>> you by the ears and shake you” way but rather something more subtle. This
>> for me is more where I’d like to be.
>>
>> Please understand I’m not trying to dissuade Pete or anyone else from
>> doing their own experiments and coming to their own conclusions. One of
>> the great things is that there’s a lot of different places to go and a lot
>> of potential things to discover. It’d get dull fast if we all went in the
>> same direction!
>>
>> Regards,
>> Tom
>>
>>> On 14 Sep 2017, at 22:55, ijfritz at comcast.net wrote:
>>>
>>> Hmmm ... not sure about all that.  I have a VCO that has ten-step
>>> waveform generators.  I can make timbre changes by shoving the sliders
>>> around.  To my ear the changes sound smooth, even if fairly extreme.
>>> Same thing with the extreme waveforms in my 5 Pulser waveshaper.
>>> Remember, you almost always hear a strong fundamental frequency when
>>> doing this kind of morphing.  (Unless you deliberately suppress it.) But
>>> tell me, why would you want to morph between two low-harmonic content
>>> waveforms anyway?  I mean why would you do it this way instead of by
>>> simple means?
>>>
>>> I think it would be quite interesting to listen to dynamically changing
>>> Walsh-generated waveforms. There could well be interesting dynamic
>>> "phasy-ness".  Or interesting initial note transients. Or cool
>>> audio-frequency timbre modulation effects.
>>>
>>> Carry on Pete!  I've been working on extreme waveshaping for over thirty
>>> years, and several modules based on this work have been successfully
>>> commercialized.  I think you will almost certainly get some interesting
>>> results.  And of course it would be easy to generate these dynamic
>>> waveforms with simple code or simulations.
>>>
>>> Ian
>>>
>>>
>>>
>>>
>>> Sent from XFINITY Connect Mobile App
>>>
>>>
>>> ------ Original Message ------
>>>
>>> From: Tom Wiltshire
>>> To: Pete Hartman
>>> Cc: synth-diy at synth-diy.org DIY
>>> Sent: September 14, 2017 at 5:02 AM
>>> Subject: Re: [sdiy] Walsh Functions/EN S-008
>>>
>>> Isn’t the trouble with Walsh function synthesis that each coefficient
>>> controls a complex waveform with a whole fistful of harmonics? While it’s
>>> possible to carefully mix Walsh functions to get smooth-sounding
>>> waveforms by cancelling out higher harmonics, any minor tweak to the
>>> coefficient values is going to introduce large abrupt edges and
>>> significant high frequencies. That makes waveform morphing pretty much
>>> bound to go from A via buzziness to B.
>>> Basing things on sine waves is so much simpler in many ways, despite
>>> Walsh functions being much easier to generate.
>>>
>>> Tom
>>>
>>> ==================
>>>        Electric Druid
>>> Synth & Stompbox DIY
>>> ==================
>>>
>>>> On 14 Sep 2017, at 05:38, Pete Hartman <pete.hartman at gmail.com> wrote:
>>>>
>>>> There are a wide range of folks on here, including some who've been
>>>> doing this stuff since ElectroNotes was young :) so I'm hoping maybe
>>>> someone can help.
>>>>
>>>> I was perusing old issues, in particular #16, which came with a
>>>> supplement S-008 on Walsh functions.  These functions were also
>>>> discussed somewhat in #16 and a couple subsequent issues.  However I
>>>> don't have a copy of S-008, and after asking Bernie about it, he has so
>>>> far been unable to locate a copy.
>>>>
>>>> I suppose if I had my head more fully around the math of Fourier series
>>>> it might not be so difficult for me, but I'm not grasping the entire
>>>> idea of using the Walsh functions for waveform generation, and I'm kind
>>>> of interested.  My thought is that while, as Bernie points out in #16
>>>> and his paper for AES, the generated waveforms themselves aren't
>>>> particularly notable, modulating the coefficients of the different
>>>> waveforms might sound different than other types of waveform modulation.
>>>>  I'm interested to play around with it in any case.  Big picture wise, I
>>>> see the parallel to Fourier and understand the concept, I'm just not
>>>> following the nature of the coefficients to generate specific waveform
>>>> types.
>>>>
>>>> I got the impression from the references to the supplement that it might
>>>> help get me over the block I'm having.  But not having it myself, and so
>>>> far unable to get one from the source (despite his much appreciated
>>>> search for same) the question turns to whether any of y'all out there
>>>> might have a copy of S-008?  If so, and if we can get Bernie's blessing
>>>> (and probably send him a copy too), I'd be interested in some form of it
>>>> that I could read.
>>>>
>>>> Thanks!
>>>>
>>>> Pete
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>>>
>>>
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>>
>
>
> --
> ijfritz.byethost4.com
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