[sdiy] VERY cool/bizarre: Buchla noise

[Harry Bissell Jr]

Shift register noise is PSEUDO-random... it does
not truly contain ALL possible frequencies... it is
quantized to discrete frequencies (depends on the
shift
register length and clock rate)

It also repeats exactly the same sequence every time.

Now...  should you care ?

The (may its elecrons rot in hell) MM5837 has a repeat
time of 1-2 seconds... corresponding to a lowest
frequency of .5Hz to 1 Hz.  In its proper use as a
noise source for room equalization, this is really not
an issue... in fact the guaranteed flat frequency
response higher in the useful audio range is a feature
compared to noisy transistor junctions..

Its just if you want to LISTEN to it that it sucks!  
Human perception to 'time' rather than frequency can
easily pick out the repetitions. 

I still cannot believe that SEQUENTIAL CIRCUITS used
this dog-chip in the ProphetV (Rev3.2)  All I can
think
is that they saw the data sheet. designed it into the
board, then listened with UTTER HORROR when they heard
what they had created :^P

H^) harry


--- Metrophage <c0r3dump23 at yahoo.com> wrote:

> Why I was guessing that it is not random was because
> of the audible
> 'thump', like a badly timed loop. I was figuring
> that even if it
> repeated, random distribution of frequencies would
> mean that the
> transition from end to beginning would still sound
> just as smooth as
> any other instance.
> 
> CJ
> 
> -- Rainer Buchty <rainer at buchty.net> wrote:
> 
> > >I think you've nailed it right there! It is not
> random.
> > 
> > *No* PRNG (i.e. noise generated by a feed-back
> shift register) is
> > true
> > random but shows a periodic behavior. That's why
> you should use at
> > least
> > 22, 23 Bits so that pattern repeat takes place in
> the domain of a few
> > minutes rather than seconds.
> > 
> > Rainer
> > 
> > 
> 
> 
> 
> 		
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