[sdiy] Popcorn Noise Generator?

[Ray Wilson]

For people who are wondering what popcorn noise is...

Quote from "INTUITIVE IC OP AMPS FROM BASICS TO USEFUL APPLICATIONS" (not 
shouting the title really is all caps)
Author: Thomas M.Frederiksen
National Semiconductor Technology Series
Copyright 1984 Thomas M.Frederiksen

START QUOTE
"Popcorn" Noise. A peculiar additional ac noise mechanism is sometimes seen 
when an oscilloscope is used to observe the output ac noise voltage of an op 
amp. Digital signalling from outer space seeme to be taking place. Pulses 
can exist with widths of many milliseconds where the constant baseline of 
random ac noise abruptly steps up by a large enough factor (say, 5:1) to 
trace out a rectangular pulse, with the baseline ac noise now occuring 
across the top of this pulse, as shown in figure 3-30. This abrupt type of 
noise is called popcorn noise because of the sound it makes coming from a 
loudspeaker. Popcorn noise is caused by a defect that is dependent on the IC 
manufacturing technique.

This ac noise results from abrubpt changes in the input current between the 
normal level and a second, qusistable level that differs by approximately 
100 pA. Evidence of popcorn noise is closely monitored by the manufacturer. 
however to guarantee that it is not present requires special, time consuming 
(and therefore expensive) testing.
END QUOTE

Testing and manufacturing techniques, I'm certain, have come a long way in 
21 years so I'd bet this is not as prevalent as it used to be.

Cheers

Ray





----- Original Message ----- 
From: "Ray Wilson" <raywilson at comcast.net>
To: "harrybissell" <harrybissell at prodigy.net>; "Glen" <mclilith at charter.net>
Cc: <synth-diy at dropmix.xs4all.nl>
Sent: Saturday, July 09, 2005 6:27 AM
Subject: Re: [sdiy] Popcorn Noise Generator?


> The grainy noise generator is white noise through a window comparator. The 
> window is adjustable so you get a few clicks or a lot of clicks.
>
> Ray
>
> ----- Original Message ----- 
> From: "Glen" <mclilith at charter.net>
> To: "harrybissell" <harrybissell at prodigy.net>
> Cc: <synth-diy at dropmix.xs4all.nl>
> Sent: Friday, July 08, 2005 8:40 PM
> Subject: Re: [sdiy] Popcorn Noise Generator?
>
>
>> At 10:14 PM 7/8/2005, harrybissell wrote:
>>
>>>how about start with white noise, then rub it into an active diode
>>>section biased so that only peaks above a DC level would be passed.
>>>
>>>Those peaks would still be analog (of varying amplitude) but would become
>>>less frequent as the DC level was increased.
>>>
>>>alternately you could get an old Gershon Kingsley record and have some
>>>REAL popcorn noise...
>>>
>>>H^) harry
>>
>> What about feeding white noise through a narrow window comparator? That 
>> would make all the spikes the same amplitude, but is that really what we 
>> would want, if trying to generate popcorn noise?
>>
>> What about a weak radioactive source, and a Geiger Mueller tube?
>>
>> What about sampling the voltage drop across a blinky neon lamp?
>>
>> I'm just wondering. I have to admit that I'm not totally sure what 
>> isolated popcorn noise sounds like. I've heard a few audio amps which 
>> popped and cracked due to a circuit failure, but I don't know if that's 
>> really popcorn noise.
>>
>> Does anyone have a reference wav sample of the stuff?
>>
>> thanks,
>> Glen
>