Wiardgroup

Must be a typo.

Here is the correction:

"n+1" AUX OUT is a voltage based on a number between 0 and  
8 plus one. Each value of n is related to the next as allowed by 
the CHANCE and CHANGE settings. n+1 out is a linearly 
weighted DAC.

> Is this a simulation of Brownian motion? (Ref - Fractal 
Geometry of Nature by Mandelbrot, pages 12, 13, 233)

Brownian motion is a infinite 2 dimensional matrix function with 
independent coordinates. The Noise Ring outputs are not 
independent.
>  

Correction:

> But what does the "2^n" OUT voltage represent? 2^8 is 256. 
2^n out is an exponentially weighted DAC

>  
> And in the block diagram for the NOISE RING - why does each 
bit in the shift register have a line connecting it to the DACs?

Those are the 8 bits that get changed to 256 voltage levels.
>  
> 
> drmabuce <drmabuce@y...> wrote:
> 
> Hi Justin
>      i hope you will forgive the intrusion, as your email
> specifically addressed Grant. And  i hope Grant will respond as 
well
> because you can bet he will have something interesting to say. 
But
> your question is just too juicy to pass up. It touches on a lot of
> very critical issues concerning analog module designs.
>      An "OTA" (Operational Transconductance Amplifier) can be
> used as a PRECISION voltage controlled resistor (it has other
> applications as well but that's a whole `nother story).
> Analog synthesis is one of the realms where voltage control is 
STILL
> , pretty much, THE crucial method of control.  A device that 
turns a
> voltage into a resistance is one of the handiest things 
designers can
> have in their toolkits when they set out to steer voltage on 
complex
> courses.  Now, there are a bunch of components that can pull 
this
> conversion off. Diodes, Transistors,  Photoresistors, even
> M.O.V's can do this trick too. But the distinguishing feature of
> the OTA is it's PRECISION. i don't know of any other analog
> component that yields 1v/octave scaling as painlessly as an 
OTA.
> That's why they're so desirable. Tom Henry of Midwest Analog 
> Products wrote a terrific little book called `Making Music with
> the 3080 OTA.' 
> http://www.midwest-analog.com/catbooks.html
> It's a great source of information on  OTA's in general, not
> just the venerable and capricious 3080.
>       Another issue is why they're becoming so rare.  The quick
> and dirty answer is that `science' marches on, but money
> SPRINTS ahead. It's a digital world now. The entire 
commercial
> analog hardware `industry' is barely more than a hobby for
> about a couple dozen people. It's ENTIRE annual financial
> input/output is the   equivalent of  one smallish owner-operated
> american tavern.   Digital hardware designs and software yield 
much
> greater precision and economy. The synthesizer - industry – 
moved
> there 20 years ago, so thoroughly in fact, that even experts are 
now
> hard-pressed to discern quickly whether an order for that synth 
you
> see in an EM ad will bring an actual  synthesizer, or a little
> cardboard box with a disc in it to your house (hint: the price is 
the
> best criterion). Digital hardware (and so much less, softsynths) 
have
> no need for OTA's.  The cheapest DAC can outperform the best 
OTA
> in a contest for precision. So just like steam engines the 
economy
> sets the context and OTA's are obsolete. 
>      So everybody knows that they don't make ARP2600's
> anymore but it's less widely known that they don't make the
> components with which you could MAKE (or repair) ARP2600's
> anymore either. Modern hardware design is standardized on
> surface-mount (SOIC) chips (even Grant  used this method for 
the
> noiz-ring). These chips are TINY – about the size of a booger .
> They have the advantage of being cheap,  and plentiful and, to 
be
> fair, many of the `greatest hits' of the analog chip world
> are still being manufactured in SOIC packages. But these 
lilliputian
> critters are designed for the convenience of automated 
assembly lines
> not human fingers. As Grant has pointed-out, manufacturers 
have
> stopped making many OTA types altogether  So the only stocks 
in
> existence are in the discontinued stock of distributors and 
prices 
> are adjusted accordingly until they're all sold and then it
> becomes an auction. In this sense EVERY piece of analog 
gear is a
> limited edition!
>       This screed is not the whole story of course, there are many
> corollaries to the axiom "all things must pass' (the tube
> renaissance, handmade discrete op-amps etc.) but beware! I 
can
> prattle on for hours about that too! 
>       i can't say this enough:  get `em while you can.
> 
> 
> 
> 
> 
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