The ASM-2 NOISE Module


The Noise module provides the basic material to produce a whole spectrum of sounds that do not have a defined pitch.

White noise can be used to produce sounds such as wind, rain and surf.

`Coloured' or `Pink' noise, which is white noise with the low frequency components boosted, is used for sounds having a strong bass content, such as the rumbling of thunder. The ASM-2 takes the fixed `pink' noise circuit of the ASM-1 and adds two new controls that allow the user to increase or decrease the Red (higher frequency components) and the Blue (lower frequency components) of the `coloured' noise and provides a more flexible noise source.

A further, third stage, provides a random voltage output.

In addition to modulating VCO signals, noise can be added to these signals to simulate wind noise in organ pipes and woodwind instruments.



        • White Noise (~5V peak-to-peak)
        • Coloured Noise (Red and Blue independently adjustable) (~5V peak-to-peak)
        • Random Voltage (~5V peak-to-peak)

The ASM-1 Noise module provided three fixed filter output stages in its module to provide a White, a Pink and a Random output signals. The ASM-2 develops this further by replacing the fixed `Pink' stage with a dual adjustable `Red' and `Blue' stage to offer more flexibility to the range of sounds provided. However it is a fairly trivial modification to restore this design back to the original ASM-1 variant. Details for this retro-modification are included in the schematic.


Terry Mikulic
"Reader's Equipment - Four Analog Circuits from Terry Mikulic"
Electronotes, Vol. 5, No. 34, Jan 25, 1974, pg 16

Bernie Hutchins
"The ENS-76 Home-Built Synthesizer System - Part 8, Noise Sources"
Electronotes, Vol. 9, No.76, Apr. 1977, pp 3-4

Copyright 2000. All rights reserved.     Revised: December 12, 2006