Manual

doepfer
System A - 100
NOISE / RANDOM A-118
3
3. Controls
The A-118 produces white and colored noise.
White
noise contains all audio frequencies, at random ampli-
tude. 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
pink noise
. This also contains
all audio frequencies, but with equal weighting for each
octave rather than each frequency, so the higher
frequencies get progressively quieter (see Fig. 1).
Fig. 1: Spectra of white and pink noise
1 Blue
Use control
1
to adjust the amount of
blue noise
(the
high frequency components) in the signal at
output
"
.
2 Red
Use control 2 to adjust the amount of red noise (the
low frequency components) in the signal at
output
"
.
3
Rate
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 colo-
red 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.
1 Hz 15 Hz 20 kHz
Frequency
➨
➨➨
➨
pink
white