UBZR1 Noise Generator Module
Summary/Usage
The Noise module serves two purposes:
- a white of pink noise audio source to synthesize non-periodic sounds
- a pink or "red" noise source to use for random type modulation
Functional Description
The noise module uses a transistor operated in reverse mode above
breakdown voltage with current limited.
The following opamp circuits filter for
- white noise
- pink noise with a flat power spectrum per octave: d p / d ln f =
constant
- "red" noise with still more emphasis on low frequencies than pink
noise.
Final amplification is done with an LM 13700 transconductance
amplifier, which serves as a built-in VCA and provides for two
separate current outputs, one for white/pink noise and one for
pink/red noise. The former can be used in the audio path, the latter
is available in the modulation matrix.
Performance Specs
‑ to be documented ‑
Schematics as SVG Files
Interface
Inputs
- Continous control voltage (−5 V to +5 V) input to control volume (output #0)
- Continous control voltage (−5 V to +5 V) to further adjust output
amplitude of Pink/Red output (output #1). To be connected to a
"wheel" control
- Logic level input (0 V or +5 V) to switch off output #0 (at logic
level +5 V)
- Logic level input (0 V or +5 V) to select between white or pink
noise for output #0
- Logic level input (0 V or +5 V) to select between pink or red noise
for output #1
In UBZR1, that latter two inputs are wired together outside of the
Noise module board, because outputs #0 and #1 are not likely to be
used at the same time.
Outputs
- White/Pink current output (−0.5 mA to +0.5 mA maximum)
- Pink/Red current output (−0.5 mA to +0.5 mA maximum)
Acknowledgements
gmx.de
