doepfer
A-118
NOISE / RANDOM
System A - 100
1. Introduction
Module A-118 (NOISE / RANDOM) is (as you might
have guessed) a
tor.
NOISE / RANDOM A-118
noise and random voltage genera-
White
Colored
Random
Output
Random Control
- +
Blue
Red
Rat e
Level
It produces three types of signal: white noise, colo-
red noise, and random voltage.
White and colored noise can be used as audio sources, and also, in conjunction with a sample & hold
module, as control voltages, and the random voltage is
a useful source of voltage control, especially for its low
frequency content.
The A-118 gives you the ability to mix the relative
amounts of
noise (high frequency component) in the colored noise
output.
There are knobs to control the
amplitude of the random voltage, and two LEDs indicate the state of the voltage at any one time.
(low frequency component) and
Red
rate of change
Blue
and
1
A-118
NOISE / RANDOM
System A - 100
doepfer
2. NOISE / RANDOM - Overview
A-118
RANDOM
White
➊
Colored
➋
➌
Random
Output
NOISE /
0
0
0
0
-
+
Blue
10
Red
10
Rate
10
Level
10
Random
Control
➀
➁
➂
➃
➄
Controls:
: Control for blue noise component at
Blue
1
colored noise output
"
2 Red: Control for red noise component at
colored noise output
"
3 Rate: Control for the cycle time of the
random voltage at output
Level: Control for the amplitude of the ran-
4
§
dom voltage at output §
5 Random Control: LEDs indicating the state of the
random voltage at output
§
In / Outputs:
! White: White noise output
Colored: Colored noise output
"
Random Output: Random voltage output
§
2
doepfer
System A - 100
NOISE / RANDOM A-118
3. Controls
The A-118 produces white and colored noise.
noise contains all audio frequencies, at random amplitude. The spectrum of white noise is completely flat ie. each section of the sound spectrum contains the
same amount of energy (see Fig. 1).
Another type of noise is
all audio frequencies, but with equal weighting for each
octave rather than each frequency, so the higher
frequencies get progressively quieter (see Fig. 1).
1 Hz 15 Hz 20 kHz
Fig. 1: Spectra of white and pink noise
pink noise
pink
. This also contains
white
Frequency
White
➨➨➨➨
1 Blue
Use control 1 to adjust the amount of
high frequency components) in the signal at
output " .
blue noise
(the
2 Red
Use control 2 to adjust the amount of red noise (the
low frequency components) in the signal at
output " .
Rate
3
Use control 3 to adjust the cycle time T of the
random voltage at output §. T is a theoretical figure,
because of the random voltages the module produces.
In practice, a setting of 0 on the knob means fast
changes in voltage, producing a spectrum similar to
pink noise (see Fig. 2); and 10 means slow changes
(see Fig. 3).
Remark: The random voltage is derived from the colored noise output by low pass filtering. Consequently
the settings Blue and Red will affect the random
output. If desired the random voltage can be derived
from the white noise output. Please refer to the A-100
service manual or contact Doepfer if you want to
modify your A-118.
3
A-118
Fig. 2: Random voltage with Rate = 0
NOISE / RANDOM
System A - 100
5 Random Control
Use these two LEDs to keep track of whether the
random voltage is positive (+) or negative (-) at any
point in time. Their relative brightness also shows
amplitude.
4. Outputs
! White
Output ! produces white noise.
" Colored
doepfer
T
Fig. 3: Random voltage with Rate = 10
4 Level
The amplitude of the signal at output § is adjusted with
this control.
4
Output " produces coloured noise, whose spectrum
is determined by the position of controls 1 and 2.
§ Random Output
Output § produces a random voltage, whose rate of
change and amplitude are determined by controls
and 4.
3
doepfer
System A - 100
NOISE / RANDOM A-118
5. User examples
The A-118 as wind FX generator
D Patch the A-118 into an A-120 VCF as below. Set
CV2 to zero, the frequency to a mid position, and
the resonance to just below self-oscillation.
Now increase CV2’s level. An irregular wind sound
D
should emerge. Knobs 3 and 4 on the A-118
control the rate of change and amount of this
irregularity. 1 and 2 control the wind’s timbral
content.
CV 2
Audio In
Audio
Out
A-120
VCF 1
Frequency
Resonance
A-118
NOISE / RANDOM
Blue
Red
Rate
Level
Random Control
- +
Colored
Random
Output
CV 2
Level
Random arpeggios
In this example, momentary random voltages from the
A-118’s random output are captured by a
& Hold Module which is itself triggered by an LFO.
Every time the LFO completes a cycle, a new random
note is played by the VCO. It’s possible to patch a VCA
in before the VCO, and, by adjusting the gain and
output parameters, control the frequency range of the
arpeggios.
A-118
NOISE / RANDO M
Random
In
Trig. In
CV 2
VCOS&H
LFO
Sample
: Using the A-118 and A-120 for wind noises
Fig. 4
Fig. 5: Rhythmic random arpeggios
5
A-118
NOISE / RANDOM
6. Patch-Sheet
System A - 100
doepfer
The following diagrams of the module can help
you recall your own Patches. They’re designed so
that a complete 19” rack of modules will fit onto an
A4 sheet of paper.
Photocopy this page, and cut out the pictures of
this and your other modules. You can then stick
them onto another piece of paper, and create a
diagram of your own system.
Make multiple copies of your composite diagram,
and use them for remembering good patches and
set-ups.
P • Draw in patchleads with colored
pens.
• Draw or write control settings in the
little white circles.
A-118
NOISE /
RANDOM
White
10
0
Colored
10
0
10
0
Level
10
0
Random
Control
-
Random
Output
+
Blue
Red
Rate
A-118
NOISE /
RANDOM
White
10
0
Colored
10
0
10
0
Level
10
0
Random
Control
-
Random
Output
+
Blue
Red
Rate
A-118
NOISE /
RANDOM
White
10
0
Colored
10
0
10
0
Level
10
0
Random
Control
-
Random
Output
+
Blue
Red
Rate
6
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