Yamaha CS-30 Owner's Manual page 5

t.
creates the tone by changing the harmonic structure
by cutting, or emphasizing, with the filter a part of
the harmonics of VCO-produced sound source having
a l a r g e n u m b e r o f h a r m o n i c s .
The VCF creates the tone by changing the cut-
off frequency (existing on the borderline between
the passage and shield-off sections) by controlling
the voltage. To eliminate any harmonics structure
deviation (KEYBOARD FOLLOW) caused by the
difference in intervals. it is designed so that the
cut-off frequency will shift along with the shift in
the interval, by adding the KEY VOLT voltage of
the keyboard circuit to the DC voltage generated
with the use of the control. The tone can be rendered
with a timewise variation by adding to these con-
trol voltages a voltage such as that of the LFO, or
EG, that changes with time as in the case of the
V C O .
The drawing at the right illustrates the mode in
which the cut-off frequency of the LPF is controlled
b y t h e E G .
V C A ( V o l t a g e c 0 n t r o l l e d a m p l i f i e r )
The VCA is an amplifier block whose amplifica-
tion degree is varied by the control voltage.
The drawing at the right shows a case in which
the arnplification degree of the amplifier is controlled
by the EG voltage to give a timewise variation
(envelope) to the volume, from the point the sound
starts up to the point it fades away. Naturally, as
in the cases of the VCO and VCF, it is possible
to add a voltage such as of the LFO to the EG
voltage and use the resulting voltage as VCA's con-
t r o l v o l t a g e .
E G ( E n v e l o p e G e n e r a t o r )
The EG has the function of producing the voltage
curve that indicates the condition in which the
sound changes in order to render the sound with a
timewise variation. Given a signal to initiate the
start and end of the envelope by the TRIGGER
voltage of the keyboard circuit, the EG generates
signals that will be used as the control signals for
t h e V C O . V C F . V C A . e t c .
ln addition to the elements described above, the
synthesizer has such elements as the LFO (low
frequency oscillator) that functions to give a peri-
odical variation. and controls to enhance the effects
of the performance. But in any case, the fact re-
mains the same that something is controlled by
changing the voltage.
In this way, since all controls in a synthesizer are
effected by using the voltage value as a medium,
the synthesizer is capable of producing various
variations of sounds with ease.
C U T O F F F R O .
- ....-
KEY VOLT
A I V l P L I T U D E
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K E Y - O N K E Y _ O F F O N O F F O N
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