Wiardgroup

Hi Mathieu
In order to avoid re-inventing the wheel, please read the circuit
desciption Grant posted at:

http://www.wiard.com/1200/NR/Noise_Ring.html

i will be referring to the block diagram he posted.

but first....
regarding digital noise:
If we force a feature-by-feature comparison of the I.D. and the N.R,
the one feature that the N.R. lacks is a 'conventional' digital noise
source. The main and aux outputs of the N.R. are both digital noise ,
to be sure, but they are both variable in spectrum and controlled by
the two CV vectors, "Change' & Chance'. This makes them a little
different from conventionally produced digital noise sources (such as
the now extinct MM5x37 chips).

In any case, your Hewlett Packard device is supplying plenty of
flavors of 'conventional' digital noise and so you're covered there.

As for a comparison of the approaches...

The Blacet I.D. is a very full featured implementation of a tried and
true, time-honored method of random voltage generation in analog
modulars. To wit, a noise source (continuously variable between
digital or analog) is 'snapshotted' by a sample hold at a voltage
controlled sample rate and output as random steps. The pattern of
these steps vary in amplitude according to the spectrum of the input
noise and , in duration by the clock rate. Thus, the output steps are
derived dirctly from the noise sources, analog , digital or some mix
of both.

The Wiard N.R. uses analog noise at a basic source point in it's
algorithm, but never directly. This noise is never sampled by an
sample/hold circuit, in fact there are no sample/hold circuits in the
N.R and this is a fundamental distinction.
(It will help to consult the N.R. block diagram, at this point)
You may already know how a shift register works but for anyone who
doesn't, i'm going to use the analogy of a conveyer belt with room for
8 people....
In the N.R. , analog noise is used to tickle the threshold of a
comparator, the comparator flips on and off producing either 'someone'
or 'no one'. depending on the state of the comparator. This
person/non-person stands OFF the conveyer belt waiting for a signal.
The signal comes from the clock. The clock is also a 2-state device.
We'll call them 'tick' and 'tock'. Remember that the clock is not
steady. It varies with a CV. This is important. When the clock is in a
'tock' state , nothing happens. The conveyer belt doesn't move and no
one steps on. The N.R.'s output is static. But when the clock switches
to "tick" the conveyer belt moves one step and if the comparator was
tickled to it's 'someone' state, someone steps aboard. If it was in
'no one' state the conveyer moves one step with an empty place. On
the next tick the conveyer lurches forward and if anyone was in the
last (8th) position they get dumped off. Another thing happens at each
tick, the DAC takes a snapshot of the pattern of occupied and
unoccupied places on the conveyer, and based on that pattern it sends
a voltage to the output, a different voltage for every different
pattern, Thus as the two devices, comparator and clock, go on
flickering , the conveyer gets loaded with different patterns that
SHIFT on each tick. This cycling of patterns is the heart of the
N.R.'s method, and this is very close to the classic function of a
digital shift register.
But there are some twists! And one of the more brilliant twists that
Grant conceived is depicted in the block digram by the line marked
'old data' feeding the "solid state switch' . This is controlled by
the 'Change' control. As the 'Change' control vector decreases, the
chances INCREASE that the passenger who was just dumped off the end of
the conveyer will get another turn and move right back to the front of
the conveyer again and prevents any 'new' passengers (from the
flickering comparator) from boarding. The effect of this is a
'circular' buffer wherein the pattern repeats ad infinitum until 'new'
passengers are re-introduced by increasing the change control. At slow
clock rates this results in cycling patterns. At audio clock rates the
effect is a clearly discernible pitch. The wonderful thing about this
(IMHO) is that the change control vector is continuous and thus, at
audio frequencies, random audio (noise) will start to organize itself
into a pitched tone. The 'between states' are sublime (to my perverse
ear, anyway) and if you descend into chaos again , when you morph to
pitch the next time there's no guarantee that you'll get the same wave
as before.
Please forgive me for editorializing, but the resulting patterns are
exquisite!!!
i'm sorry to confess my fetish, but that's just the very definition of
my personal idea of a good time!
=)

To drag this screed back to the issue of comparison. The method of
pattern generation just described is very different than the
sample/hold method used by the I.D. (and MANY other RVG is modular
synth history).
Most importantly, this method yields a very different character of
output patterns than a sample/hold-based design produces. The noise
sources are never sampled directly and thus, the output SOUNDS
different from sample/hold-based output.
i've foolishly engaged in past disputes about whether this is can be
called 'random' or not, and if it IS randow, how random is it???...
(see ***) That's a semantic issue and a waste of time. The bottom
line is that the noise ring yields MUSICALLY interesting patterns (to
my ear) and that's what matters. In all fairness, Sample/holds yield
interesting patterns too (i have 9 versions of them , at last count)
but the noise ring's output is distinct from all of them. The other
very important distinction is the effect of the ability to exercise a
very fine level of control over the 'chance' and 'change' parameters.
This is a unique and VERY powerful feature.

i'm sorry for the screed, and i hope you'll think carefully before
saying it's ok for me to disgorge 'a bunch of information' ever again!
Be careful what you wish for...
;'>

best wishes,
-doc

*** a true 'Random Generator' would output a series of unpredictable
voltages, turn into Katie Couric, sternly lecture Peter Grenader his
sock choices, turn into the erased sections the white house tapes, bob
for silver apples on the moons of Mercury, ride with Elvis in a
Lincoln to the color magenta, Win the civil war in overtime and rename
everyone to "pamela" , hide a bobble-head doll of Spiro Agnew in the
ghost of Elmer Fudd's sock drawer, eradicate the letter "J", change
your sex to 'yes', play the B3 solo from "Roundabout' and then do
nothing for 43 trillion years while simultaneously going back in time
and derailing the Big Bang before it starts...... i think even prof.
Richter would have a tough time with THAT design....maybe the
envelooper...one can always hope

--- In wiardgroup@yahoogroups.com, "matthieuvandiepen" .>
wrote:
>
> Hi Doc,
>
> > While i realize that the I.D. and the N.R. are both considered
> > random voltage generators, under the hood, they are VERY different
> > devices. But let me ask a couple of basic questions before i spew a
> > bunch of information that may be of no interest to you at all...
>
> Well i'm very interested to hear this bunch of information, so
please go
> ahead!!!
>
> >
> > Is the difference between analog white noise and digital noise
> > critical to your application?
> >
> Actually difficult to say, but i understand that both the NR and the
ID are
> generating analog white noise, but why could it be critical to an
application?,
> i'm very interested to learn more about the possibilities of noise
>
> > and...
> >
> > do you already have a digital audio noise source?
>
> Yes i have one, i have a Hewlett PackerD HOI-3722A Noise generator.
Which
> is a scientific unit. I think it's digital. But it can make a lots
of (different) noise...
>
> >
> > The answer to those questions makes a difference in the comparison.
> >
> > -doc
>
> Well i'm very interested to hear more about this subject,
>
> Thanks Matthieu
>
>
>
> >
> >
> > --- In wiardgroup@yahoogroups.com, "matthieuvandiepen"
> > wrote:
> > >
> > > Does anybody know the differences, the pros, the cons of the two
> > noise units:
> > >
> > > Wiard noise ring versus Blacet improbability drive
> > >
> > > - if you have the noise ring, can you do without the ID? Or does it
> > have some sides which
> > > the noise ring doesn't cover?
> > >
> > > Thanks very much,
> > >
> > > Matthieu
> > >
> >
>