|The triple noise module contains three separate analogue noise circuits which use transistors as noise source.
The noise signal can be obtained at the white noise output, slightly filtered at the coloured noise output and extremly low passed at the random output.
The voltage level of the random signal can be adapted with the rate pot and is visalized with a LED display.
The schema comes from the book "Formant Pro MSS 2000" by H.J. Helmstedt.
Noise 1: White noise which is modulated by an ADSR controlled VCF.
Noise 2: Random signal which controles a VCF which modulates a triangle VCO signal.
Noise 3: Random signal which modulates a VCO via linear frequency modulation input.
As this noise circuit doesn't need too much components, I placed three of them on one eurocard (picture below). You may ask: "Why the hell three noise generators in a synthesizer?!?!?" Ok, but three random signals which operate independantly might be useful by controlling different filters for instance.
To find three capable noise transistors was quite a lot of work, as nowadays transistors don't have that much noise signal they had in the years before. I checked ca 50 transistors and chose the three mountain cocks of them, and one of them is the king of rock'n roll: 10 Vss noise amplitude with this circuit!
Another amplification step (like René Scmitz proposes with his circuit) could enhance weaker noise signals.
Three noise circuits on one eurocard.