Super Simple 1 Transistor White Noise!

[timd]

I have been looking through many schematics for a low parts count simple white noise generator (with a discernible input) that runs off 9V. While I didn't find any that meet those requirements, I made my own:

You can use any NPN transistor, but I have found a 3904 to be good. The best hissy one I found (the one I used for the pedal) was in my "salvaged" transistor bin. Its stamped 169C (company code?) and is great. So, here's how to get that sound:

E - No Connection

B - Input (use an input cap to taste) / Output (use cap)

C - 9V+ via a 10K resistor. Connect to outside lug of a 5K pot via a capacitor. Inside lug to 9V+

*No connection to ground

[Digital Larry]

NOW I get what's going on in some of those Devi Ever pedals!  (I think) Thx.

[timd]

No problem. Its just a fun little circuit.

[Digital Larry]

Nice wind sounds!  I grabbed a coat and it's 80F here today!

Hahaha I love the enclosure.

http://en.wikipedia.org/wiki/Noise_generator

You could come up with a whole line of them - transistor, diode, zener, cork-sniffer, etc.   

[deadastronaut]

you might like this then... clip on page 2.

http://www.diystompboxes.com/smfforum/index.php?topic=81602.20

[LucifersTrip]

sounds cool...good to see some different, simple stuff.   if E is not connected, can you just use a diode?

[Digital Larry]

sounds cool...good to see some different, simple stuff.   if E is not connected, can you just use a diode?

Seems like that would be possible.  Check this wikipedia article. 

http://en.wikipedia.org/wiki/Noise_generator

I'd be interested to see what a > 7 V Zener diode's noise sounds like.  This description is just screaming out for a little marketing-hype-spin: "For breakdown voltages greater than 7 volts, the junction width is thicker and primary mechanism is an avalanche. The noise output is more complicated. There is excess noise (i.e., noise over and above the simple shot noise) because there is avalanche multiplication."

[timd]

sounds cool...good to see some different, simple stuff.   if E is not connected, can you just use a diode?

A diode connected where?

[timd]

Also, are there any issues with the circuit itself not connecting to ground? 

[moosapotamus]

sounds cool...good to see some different, simple stuff.   if E is not connected, can you just use a diode?

A diode connected where?

Instead of the transistor.

[Rob Strand]

Check some of these out,

http://schematicsforfree.com/archive/file/Oscillators%20and%20Generators/Pink-White%20&%20Other%20Noise%20Generators/Pink%20&%20White%20Noise%20Generators%20-%20Misc.pdf

Particularly,

p22 ETI 442

p1, p4  same circuit as p22 but with a zener, the problem with zener is you need a higher supply voltage
            (often not as good as a transistor at low voltages)

This is the same idea but using an opamp to amplify,
http://www.digisound80.co.uk/digisound/modules/80-12/construction/80-12_ETI.pdf

[timd]

For that Wiki zener diagram - I have a couple questions. Why the "U" in front of the circuit in and outs? Also, which is positive and ground rail? Would 9V be substantial enough to get a good hiss out of that setup? I assume you would want R to be variable to make adjustments.

I could see running 2 or 3 of these in series with different size pots, or running my original and this one together in a circuit. Any thoughts?

[toneman]

some classic noise synths here:
most of them use a single transistor for the noise source.
add a buffer and a filter and you can get any "color" noise you want

white, pink or red....choose your color  

NEW NOISE MODULE:
http://www.paia.com/talk/viewtopic.php?f=6&t=507

SURF:
http://www.paia.com/talk/viewtopic.php?f=6&t=492

CHATTER JAMMER:
http://www.paia.com/talk/viewtopic.php?f=6&t=73

THE WIND:
http://www.midimanuals.com/manuals/paia/3730_the_wind/assembly_and_using_manual/

afn

[PRR]

> Why the "U" in front of the circuit in and outs?

The international abbreviation for Voltage is "U".

> Would 9V be substantial enough to get a good hiss out of that setup?

Yes; but 8V is much worse. This plan is notoriously weak on battery systems where a "9V" battery can drain to 7V.

Can a diode be used? It must break-down. And <6V breakdown diodes don't hiss big. 1N4148 etc diodes break-down at >50V, which may be awkward. For "9V" applications you want a 7V breakdown. You can buy a 6.8V or 8.2V Zener. But 99% of 2-cent transistors have emitter-base breakdown very near 7V. Same thing, ignore the extra leg.

> I assume you would want R to be variable to make adjustments.

Hiss voltage is low. You *always* need an amplifier after the diode. So pick a current that is small, but not real small. 10K-100K usually works. Put a volume control after the first stage of amplification. (I see PAiA does trim the diode current as a "level" control, but this also interacts with the amplifier they use. IAC, this won't trim to zero output, which can be useful.)

[timd]

So the bottom rail is ground I assume?