[sdiy] preferred noise source circuits

[Adam Schabtach]

It's also far simpler to generate mathematically correct pink noise with a
microprocessor (i.e. with software) than with analog circuitry. I learned
this years ago when I wrote the pink~ object for Cycling '74's MSP.
Unfortunately I don't have any references handy to cite, and I suppose it
would be a violation of their copyright for me to post the source code here
(if I still have it, which I'm not sure that I do). Google should help the
curious as always, though.

So, I'm in agreement with Tom. You could build a dandy white and pink noise
source with one microprocessor. OTOH if hardware's your thing and software
isn't, then you're welcome to use many more parts to create an approximation
of the same result.

--Adam

> -----Original Message-----
> From: synth-diy-bounces at dropmix.xs4all.nl 
> [mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Tom 
> Wiltshire
> Sent: Tuesday, June 23, 2009 7:55 AM
> To: Amos
> Cc: sdiy DIY
> Subject: Re: [sdiy] preferred noise source circuits
> 
> Well, if we're talking about "white" noise, then I mean noise 
> that is genuinely white - i.e. has an equal distribution of 
> energy across all the frequencies of interest (the audio band 
> in our case). That's not really subjective at all. Likewise 
> if you're generating random pulses or gates, then "better 
> quality" means statistically indistinguishable from random. 
> You don't want any unwanted weighting creeping in unless you 
> put it there.
> 
> Obviously whether white noise is the best kind for many 
> synthesis purposes is a much more subjective issue. Perhaps a 
> 6dB rolloff of the high end makes a better audio noise source 
> since it doesn't sound so harsh. If you've got good quality 
> white noise to start with, then you can choose what you do to 
> it. If it's got it's own flavour already, it's much harder to 
> remove that.
> 
> T.
> 
> 
> 
> On 23 Jun 2009, at 12:38, Amos wrote:
> 
> > On Tue, Jun 23, 2009 at 6:09 AM, Tom Wiltshire 
> <tom at electricdruid.net> 
> > wrote:
> > "a digital noise source with a simple 8-pin DIP microprocessor that 
> > will give you much better noise quality than most analogue noise 
> > sources."
> >
> > see now, I don't mean to stir the pot, but "much better 
> noise quality" 
> > seems pretty subjective to me.  This is what it (ought to,
> > IMO) come down to when choosing your noise source.  What 
> qualities do 
> > you evaluate when determining "goodness" of noise?
> > This is more an open question for anyone who has an opinion on such 
> > things.
> >
> 
> 
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