[sdiy] reverse biased NPN vs Zener diode for noise...

[Oren Leavitt]

Any noise in the op-amp gain stage will certainly be insignificant 
againt that coming from the diode.
You prbably wont need a lot of amplifier gain if you find a really noisy 
diode.

cheater cheater wrote:
> What if you use an op-amp to amplify the noise output of the silicon
> diode? Will that introduce unwanted noise?
> 
> D.
> 
> On Mon, Nov 2, 2009 at 07:52, Oren Leavitt <obl64 at ix.netcom.com> wrote:
> 
>>Find old zeners from the 1960s, and about 8 volt or higher. You will likely
>>find some really nice noise makers. Modern zeners are made with a different
>>process that does not yield as much noise.
>>The fun with "old" zeners is that each doide has its own individual
>>character, color and grainy-ness. Don't be surprised if you find yourself
>>giving your diodes names :-).
>>
>>- Oren
>>
>>nicolas wrote:
>>
>>>I haven't done any comparative testing, but the advantage of the zener
>>>diode is that you can order one off the shelf and it will have a known
>>>voltage drop and fairly predictable noise character.  On the other hand
>>>using a transistor you will have to experiment a bit, maybe adjust things to
>>>suit the voltage drop you find or test several transistors to find one in
>>>the right range.  My understanding is that if you do manage find a suitable
>>>transistor it will give you a bit more noise at a somewhat lower voltage
>>>drop than a zener.  With zeners, use the highest voltage you can accomodate
>>>because below 10V they aren't so noisy.
>>>
>>>Cheers,
>>>Nicolas
>>>
>>>--- On Fri, 30/10/09, Benjamin Budts <mailing at gigaspeeds.be> wrote:
>>>
>>>
>>>
>>>>From: Benjamin Budts <mailing at gigaspeeds.be>
>>>>Subject: [sdiy] reverse biased NPN vs Zener diode for noise...
>>>>To: "synth-diy DIY" <synth-diy at dropmix.xs4all.nl>
>>>>Received: Friday, 30 October, 2009, 3:13 AM
>>>>
>>>>Hi,
>>>>
>>>>I'm looking into building a noise module and I'm wondering
>>>>what the audible difference is between
>>>>reverse biased NPN based  vs Zener diode based... :-D
>>>>
>>>>Just wondering if there's somebody on the list who tested
>>>>this...
>>>>
>>>>Thx
>>>>Benjamin
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>>>>
>>>
>>>
>>>
>>>
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>>
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> 
>