Hi. I just built this white noise generator so that I can test tone controls. Thought other might be interested. It uses a reverse-biased base-emitter junction as its noise source. There are other designs that use Zener diodes, but I think that this design is cheaper and simpler.
Almost any NPN small signal transistors could be used (even low noise transistors).
The one that I built generates a handy 100mV peak-peak of white noise from 2 PN100 transistors. (100mV is about what you get striking a chord on a guitar). I haven't checked the output impedance, but it should be able to drive most loads.
Cheers!
(http://members.optusnet.com.au/~jethro.dog/mypic101.jpg)
Thanks Brett, for this nice circuit. Previously, the simplest white noise generator I'd found was designed by Rick Andersen (which is very similar to the one at Joe Davisson's site).
Some tips:
2N2222 (metal can), 2N4401, and 2N3053 (also metal can) worked well for me. I didn't have any 2N3904.
The cap from the emitter of Q1 to ground can shape the bandwidth of the noise. Larger values extend the noise into lower frequencies.
I found that a volume at the output was handy.
i'm resurrecting this because i'm curious if anyone has the schematic/layout for this.
7/24/03: A Low-Fidelity Pedal at GEO. http://geofex.com/FX_images/lofi.gif (http://geofex.com/FX_images/lofi.gif)
Here's a schem of a white noise generator that Dave Cappel designed. I made the circuit on ExpressPCB software. Remove the two 1K resistors (R12 and R13) at the end of the circuit if you're going to use a speaker instead of headphones.
The layout isn't great but will work. Put jumpers around R12 and R13 for speaker and a there's a green jumper that connects pin 10 of the IC with the center lug of the pot.
(http://i218.photobucket.com/albums/cc93/ftrock/wng-1.jpg)
(http://i218.photobucket.com/albums/cc93/ftrock/wnglayout2.jpg)