[sdiy] Diodes won't make noise

[Oren Leavitt]

Hi Ray & List,

I've found that my milage varies with zener diodes as a noise source.
Same thing with me, I have this one 1N4742 that will wake up the dead! Stick this one in any of our existing circuit designs, and they will clip! Other zeners are rather quiet.
Transistor BE junctions seem to give me more consistent results. I've found 2N5087s (PNP) to be really noisy - at least among the batch that I have.

I've seen your multi-noise source - it's nice!
A cool idea for the 'grainy' output, would be to make the span of the window comparator voltage controllable, making the 'grainyness' VC'able.

One thing I've found helpful for juction noise sources is to place the CW and CCW ends of a pot across the V+ and V-, connect the wiper to a 47K resistor, connect the other end of the 47K to the noise zener, the other end of the zener is connected to ground.  AC couple the 47K/zener to the rest of the circuit.
This way, using the pot, I am able to dial into the 'sweet' spot of the noise source and find the best 'whiteness'.

HTH,
Oren

-----Original Message-----
From: Ray Wilson <rayw at csd.net>
Sent: Oct 16, 2003 4:53 AM
To: Synth-Diy <synth-diy at dropmix.xs4all.nl>
Subject: [sdiy] Diodes won't make noise

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