[sdiy] Diodes won't make noise

[Oren Leavitt]

Good point Harry!

The 1N4742 I mentioned in my previous post is over 30 years old.

-----Original Message-----
From: Harry Bissell Jr <harrybissell at prodigy.net>
Sent: Oct 16, 2003 9:00 AM
To: Ray Wilson <rayw at csd.net>, Synth-Diy <synth-diy at dropmix.xs4all.nl>
Subject: Re: [sdiy] Diodes won't make noise

Of course the correct statement would be

zener diodes are not the good noise sources they once
were...

zener diodes (iirc) operate in two regions... a
low voltage area where they are essentially forward
biased junctions (this is for less than 5V units)and
an avalanche mode for higher voltages. So you should
be using a higher voltage zener, less than 5V units
are
about sure not to work.

That said, the higher voltage processes have been
tailored for a LONG time to get rid of the
noise...which
is a bug in a zener diode... not a 'feature'

There ARE special noise diodes, but in general you
will be more sucessful with the reverse biased
transistors...
no one expects you to run them that way so they did
not
take special care to make them quiet

H^) harry



--- Ray Wilson <rayw at csd.net> wrote:
> Hi All
> 
> In some recent experimenting with my multi-noise
> source I came to the
> conclusion that zener diodes are NOT a consistent
> source of noise sources
> (that sentence sounds a little wierd). At some time
> in the past I have used
> the specified diode and it made more noise than I
> ever saw before but that
> seems to be the rare exception. Anyway I have
> updated my multi-noise source
> module to use a selected 2N2712 or a selected 2N3904
> in case anyone is
> thinking of building it.
> 
> I also finally made boards from the artwork and they
> do work fine. I tweaked
> a couple of resistor values too.
> 
> It is here:
>
http://atlas.csd.net/~rjwsoft/multinoisemodule_exp.html
> 
> Cheers
> 
> Ray
>