70s Era Sample Hold Circuit

Noise and Random Signal Generation

let's start with a simple Noise generator. Schematic is here and board is here. You can read either and make a gerber using Autodesk Eagle.

Board image looks like this:

While Schematic is as such:

About this design

Like so many old noise boards, this one depends on noise inherent in a NPN transistor between E and B and amplifies it. I set things up so you can put test leads on the "Transemt" and "Transbase" test points and clip it to your 2N2222 or whatever transistor. Hook the output up to your studio monitor and try out transistors until you like the way the white and pink noise sound. Once you have a winner, solder the "winning" transistor into the T1 location.

For the build I ended up using, I tried a whole bunch (I mean, many, many) transistors.The one I ended up using had really good sounding pink and white noise, but the white was about 12DB too soft, stange because P2P was about the same, about 2v, when viewed on a scope. If I was building this again I'd take the unused op amp and put it in series with the white noise out so if you don't want to gain the WN up, just make it into a buffer; if you do, add some resistors to get x DB of gain.