[sdiy] Diodes won't make noise

[harrybissell]

There is an EDN Design Idea by Dick Cappels that has a transistor biased by
another transistor in his noise source. Check it out. I have not tried it, but it looks
like it might self-bias to the optimum noise point without changing the resistor
values...

H^) harry

Oren Leavitt wrote:

> 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