Noisegen

The simplest and purest way to sonify a semiconducting crystal, the noise generator isolates the fluctuations in current passing over the crystal. As the resistance of minerals and samples vary, the potentiometer, RV1 allows you to set the bias for the transistor to tune it to different materials, by passing over the breakdown thresholds of the semiconductor (which tend to be quite low in natural materials). The output requires further amplification to convert it from a fluctuating current to a voltage. This stage will be integrated in future versions, but it's nice to have such a simple circuit. Originally built with an opamp, the transistor provides a simpler approach which seemed to work more reliably with a wider range of semiconducting material. On many materials the polarity makes quite a big difference, so if it's not responding well try reversing the crystal/point contacts.

It can provide the simplest approach to listening to the difference between different minerals from different localities. There is also noise inherent in the transistor, but the difference between point contacts with pyrites and galena compared with touching ordinary metals are obvious. Also tested on a 1920's galena/cat's whisker radio point contact.

Inputs

• Two connectors for crystal (in diode setup)

Controls

• Transistor bias/current limiter potentiometer

Outputs

• Audio signal

Schematic

PCB layout