7
mini-sequencer. The knob is a "reversible attenuator" for the
control signal selected; in the photographed position, no sig-
nal will pass through to have any effect on the VCF CUTOFF FRE-
QUENCY. As the knob is rotated to the right, the selected
control signal affects the VCF directly; as the knob is rotated
to the left, the signal affects the VCF
inversely
, i.e. a posi-
tive voltage drives the VCF frequency
down
rather than up.
6. These are the AUDIO INPUT SELECTOR/ATTENUATORS for the VCF.
In the photographed position, they are all OFF.
Unless at least
one of these is "open", i.e. rotated either to left or to
right, the module will produce no sound regardless of any of
the other settings anywhere on the module panel.
The first knob on the left, labelled "VCO 1", selects either
the sawtooth (leftwards) or pulse (rightwards) signal from VCO
1 as an audio input to the VCF. The second one does the same
for signals from VCO 2. The left side of the third knob is not
connected to any signal (
except that for the first VOICE MODULE
there is a Jack at the back of the synthesizer for an external
audio signal input, and this jack is wired to the left position
of the knob on module one
); the right side is wired directly to
the output of the NOISE GENERATOR that is part of the sample/
hold in the minisequencer. Noise, filtered in various ways, is
used in the production of wind, thunder, and motor sounds, as
well as many percussion effects.
Signals from the two oscillators and the noise generator may be
mixed
in various proportions by opening all three of the input
attenuators at the same time.
7. These three rotary pots determine the behavior of ENVELOPE
GENERATOR ONE. The first two knobs set two
time constants
: the
attack time constant
is the amount of time required for the ENV
1 OUTPUT VOLTAGE to rise from 0 to maximum, and the
decay time
constant
is the amount of time required for the ENV 1 OUTPUT
VOLTAGE to fall...
...from maximum to the level set by the third knob, and
...from this sustain level back to 0.
The third knob determines, not a
time constant
, but a
voltage
constant
. This constant is the level at which the ENV I output
will be
sustained
(hence the label) for as long as a GATE sig-
nal is present at the gate input of the envelope generator.
GATE signals may originate either from the keyboard or from the
MASTER CLOCK in the minisequencer. They act as "begin-end"
instructions to the envelope generators; on the appearance of a
gate signal at its input, an envelope generator commences an
ATTACK-DECAY-SUSTAIN---cycle, and when the gate signal ends,
the envelope generator executes a final DECAY as described
