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PICList Thread
'OT: Noise generation Digital&Analog'
1997\10\21@181406 by Mattias Engstrvm

We need to implement some white noise using preferrably analog
circuitry. Is this easily achieved?
We are going to use it in a sound generation device (audio-purposes),
it through some filters, creating some hopefully interesting effects :-)

I have seen some digital random generation algoritms, can these be used
in some clever way with a D/A-R-2R ladder to produce noise? And if so,
what kind of spectral distribution does this give?

Tricky questions? I don't have a clue.

I would be grateful for any pointers

Thanx in advance / Mattias Engstršm

(BTW, thanks for all the help I got on the RS232<->TTL level conversion)

My direct email:

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1997\10\21@191134 by Clyde Smith-Stubbs

On Wed, Oct 22, 1997 at 12:00:22AM +0100, Mattias Engstrvm wrote:
> We need to implement some white noise using preferrably analog
> circuitry. Is this easily achieved?

The usual technique is to reverse bias a Zener diode, and amplify the breakdown
noise. Unless you use a special noise diode, the noise spectrum will not be
perfect, but that's probably not an issue for your purpose.

You'll need to experiment with how much amplification is required - quite
likely you can get away with one op-amp stage.

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1997\10\21@194547 by Ken Pergola

Mattias Engstrvm wrote:

   We need to implement some white noise using preferrably analog
   circuitry. Is this easily achieved?


One classic analog way is to amplify a reversed bias transistor (base and
emitter). There was a classic transistor that was used fairly widely, but
its part# escapes me at the moment. All transistors are not created equal
with regard to white noise quality from what I've read.

Try an internet search on PAIA (spelling?) Electronics, Thomas Henry, or
Polyphony magazine.

I owned a Kawai SX-210 synthesizer and it generated white noise via a
reversed-biased NPN transistor followed by two stages of amplification with
a TL082 op-amp. It may have used a 2SC536G transistor.

It sure sounded sweet!

Best of luck,

Ken Pergola

1997\10\21@195352 by Ken Pergola

Mattias Engstrvm:

Click on the link below. You'll find a transistor that is sold as a noise
source for only $1.25

PAiA Electronics --it's a great site!

Best of luck,

Ken Pergola

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