[sdiy] Re: Spiral Waveforms

[Magnus Danielson]

From: Scott Gravenhorst <music.maker at gte.net>
Subject: Re: [sdiy] Re: Spiral Waveforms
Date: Mon, 12 Apr 2004 09:26:17 -0700
Message-ID: <200404121626.i3CGQGg22122 at linux6.lan>

Scott,

> >I've yeat to understand how a "spiral waveform" behaves if it is substantially
> >different from a decaying sine (or for that matter accelerating). Given a sine,
> >you need an exponential increase/decrease generator (really just a single-pole
> >diff-system) and a VCA to control the amplitude of the sine.
> >
> >Is anyone able to draw one? Are we chasing bigfoot or could somebody please
> >explain what this "spiral" aspect is indicating.
> 
> This is where the communication problem occurred.  Neither here, nor on AH
> would Steven J. elucidate.  Some here tried to fill in the gaps; it has been
> proposed that he meant a 3 dimensional spiral form.  Imagine a "slinky"
> spring stretch out enough to pass light through it sideways.  The shadow on a
> flat surface would look like a sine wave.  A projection of a spiral.  Because
> of the confusion, some thought he meant a flat, 2 dimensional spiral.  First,
> such a spiral cannot be a function of X (or time) because there are more than
> one result value for some values of X.  And if X represents time, creating
> such a figure would require going backward in time.  I believe that Steven J.
> meant a 3D spiral form that could extend potentially to infinity.

Yes, this is in essence my objection here. If I knew one or a few examples of
a function f(t) then it would be easier. As it sounds, my two proposals for
synthesis are those which best match whatever he was out for as I could gather
it. I did look back at his postings, but had a little trouble replicating the
schematics and follow the description. Lack of concentration didn't help.

> I'm not trying to beat a dead horse (or searching for big-foot as you say), I
> want only to make sure that we aren't bypassing something that might be
> useful or innovative.

Well, I agree. If there is something potentially usefull, then we should look
at it. If it is not usefull, then we should be able to conclude that and move
on. For my own part, I think I still have too little information to actually
analyse. I did find flaws in the engineering of the circuits, but that doesn't
exclude anything. I do however question that those circuits really acheive
anything we don't know fairly well what it is. I will look at them again (with
a fresh mind) but it didn't seem like a good solution to me.

A lesson from the Lissajou-patterns is that what looks cool doesn't
necessarilly sound cool and vice versa.
 
Cheers,
Magnus