Wiardgroup

Hi Doc,

thanks very much for your wonderfull lecture on analog/digital noise.

yes i am indeed from the noisy netherlands. And i agree with you, Dutch isn't 
that different from German. It just has some more distortion in the 
pronunciation.

So i guess we now are all a lot wiser on the noise subject. I really would like 
to learn more of your other (music related) fetishes.

Some Wiard usergroup subjects i have on my wishlist are:
- vocoders (how to make a patch with a modular)
- control processors
- sequencers

Anyway, until now i want to thank you very much,

Matthieu van Diepen




--- In wiardgroup@yahoogroups.com, "drmabuce" <drmabuce@...> wrote:
>
> Hi Matthieu
> --- In wiardgroup@yahoogroups.com, "matthieuvandiepen" <matthieu@>
> wrote:
> >
> > Thank you all very much for the response! Especially Doc,still i'm 
> > wondering one thing: both modules use analog and digital noise, why 
> > is that? What is the difference? And why both use these different 
> > noise sources for different applications?
> >
> 
> i was trying to avoid this...
> ;'>
> this is a very loaded subject, and it can go in about 50 directions at
> once!
> ;'>
> and because it is one of my fetishes, i could embark on at least 25 of
> them! but i'd love to hear what some of the other eminent experts
> especially Prof Richter, on this group have to say about this subject. 
> Furthermore.... the Laurie Anderson restriction, "Writing about music
> is like dancing about architecture" applies heavily to discussion
> group  posts. 
>    There are just some qualities that have to be demonstrated live in
> order to be easily grasped. i guest-lecture at a local college and one
> of my standard presentations covers random parameters as applied to
> music. This effort started-out as one 2-hour class in the Electronic
> Music Lab but the faculty expanded it to two 2-hour sessions because
> the class consistently returned the following week with 2-hours worth
> of follow-up questions. So now i cover the subject in TWO sessions.
> 
> Suffice to say, this will only scratch the surface and before i begin
> i want to point you to some REAL authorities on the subject:
> 
> first,
> http://www.musicsynthesizer.com/Circuitry/probability.htm
> 
> Grant put up a really nifty chart that sums up the differences between
>  probablility distibutions in a column of blindingly practical and
> succinct graphs from an old test equipment reference. God Bless our
> parents generation of crusty old HAM radio veterans!!!!
> 
> next,
> http://en.wikipedia.org/wiki/Information_entropy
> 
> Wiki put up a fairly decent (for once) overview and explanation of
> Claude Shannon's definitive work on the subject  
> 
> In hard copy,
>  
> Thomas Henry put out a really nice practical book  with some great
> insights into analog noise called the "The Noise Generator Cookbook"
> but it's out of print
> 
> and finally, i personally, learned a hell of a lot from the very nuts
> and bolts treatment of digital noise and shift registers in Don
> Lancaster's wonderful "CMOS Cookbook", still in print, and still a
> GREAT reference.
> 
> Ok... here goes...
> 
> To the EE faction, the difference is pretty basic. They tend to view
> the phenomena in terms of the origin and the output. In their
> shorthand, they told me that the difference is that analog noise is a
> back-biased Zener junction, and digital noise is a just a big-ass
> shift register.
> 
> to expand :
> Analog noise originates as a sort of avalanche of electrons spilling
> over a semiconductor barrier. It reminds me of a heavily loaded
> Pachinko machine***1. In technical terms, the noise is generated by
> the Zener breakdown phenomenon in an inversely polarized
> base-collector junction. It exploits the shot noise of electrons at a
> 'choked' semiconducting gate. This physical phenomenon manifests
> itself electrically as statistical fluctuations in current flow
> present at the base of a reverse-biased bipolar transistor. (It is
> also possible to use a reverse-biased Zener diode instead of a transistor)
> The current fluctuations go VERY fast and when you amplify them a lot.
> It makes a very fast wiggly line on the O'scope. To an EE, that's
> analog noise.
> 
> Digital noise originates with a shift register that is clocked at a
> very fast rate in the audio range. The old MM5437 and MM5837 chips
> used as a one-chip noise source in many 80's era synths were
> essentially big self-clocking shift registers on a single chip. If you
> refer to my earlier post i explain how a shift-register works using a
> conveyer-belt analogy. In the case of most conventional digital noise
> sources, just consider a conveyer belt with room for many more people,
> a steady and very fast clock, and no feedback. That's how the
> randomness originates, and the output is not as wiggly as analog
> noise. It jumps very fast from step to step rather than rising or
> falling from point-to-point as analog noise does. Digital noise is
> often called 'peseudorandom' because it's randomness is finite and
> limited to the number of bits in the shift register. (spaces on the
> conveyer belt imy little analogy) As a result at some point the shift
> register method has to 'start over' and it will repeat itself. This
> manifests itself in the output audio as the infamous digital noise
> 'thunk'. The larger the number of bits in the register the longer the
> interval between thunks***2 
> 
> So...
> so far we have Wiggly, point-to-point Analog Noise generated by a
> semiconductor wired backwards, 
> and Digital Noise, hissing along in fast discrete steps with a 'bump'
> every time it runs out of bits and has to start over.
> 
> if you're listening at the output jack, the ear just kind of shrugs
> and declares that it all just kind of sounds like a hiss.... so what's
> the big deal? 
> 
> A sample hold is a sort of time-lapse photography it 'takes pictures'
> at (ostensibly) a slower rate than the change-rate of the phenomenon
> being sampled.....
> Now at this point, i bid farewell to my respected EE friends and put
> on my (rather silly and impractical) artiste hat. From here on ,my
> declarations are PURELY subjective and not only defiantly unproven but
> unprovABLE!!!!
>   When i sample analog noise at some arbitrarily fixed rate and map
> the resulting steps to pitch, my mind's melodic memory notes a
> 'character' this quality becomes clearer to me over time (and i am
> notorious and oft-chided amongst the other residents of Mabuse Manor
> for listening to this kind of crap for HOURS!!!).
> (ahem)
> But if i sample DIGITAL noise at the same clock rate my (perhaps
> arguably addled and insane) mind registers not only a higher degree of
> repetition (hmmmm THAT pitch sounded familiar!) but also a different 
> melodic character.
> Call me a head-case (and it wouldn't be the first time) but my
> artistic conclusion is that both are 'good' and i need both in my
> compositions.
> 
> That is an overall survey of 'la difference'
> and Vive Ca Difference!!!!
> 
> 
> 
> ...and to anybody still reading (what's WRONG with you???) i apologize
> again, but that's about as small a nutshell into which i can put a
> full answer to Mathieu's question.
> 
> -doc
> 
> ***1 Pachinko is a kind of small pinball machine that was (is?)
> popular in Japan. Unlike their American counterparts lots of balls
> (50-100) are in play at once and there are no flippers (at least on
> the ones i played) it's just a sort of barely controlled cascade of
> little silver balls
> 
> 
> ***2 On the MM5437, the interval was minutes long, the MM5837 beat the
> problem to a degree. Theres a good explanation at
> http://www.vego.nl/8/08/03/08_08_03.htm
> if you read German
>