Yamaha CS-80 Instruction Manual page 48

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4
44 that converts the time
interval
between
switch contact
opening and
closing into
a
brief output voltage
pulse.
The
faster
a
key
is
pressed
down,
the shorter the time
of switch contact action, and the higher the voltage
level
of the pulse.
The
key timing
circuit pulse
is
used
to create various
initial
touch
sensitivity (velocity
sensitive) effects,
depending on
how
the
presets, pro-
gramming, and
TOUCH
RESPONSE
sections are
set.
PITCHBEND
[12]
is
an
initial
touch
sensitivity
effect
whereby
the timing
circuit pulse
is
reversed
in
polarity
and
applied to the
VCO.
Thus, the
frequency
of the
VCO
is
initially forced lower by the negative
voltage pulse
from
the
Key Timer
Circuit,
and then
comes up
to the note's designated frequency
as the
pulse dies out.
The INITIAL
LEVEL
lever [43]
in
the program-
ming
panel applies the key timing
pulse to the
VCA,
thus
increasing the
volume
of
the note
for
the duration
of the pulse.
The
faster
you
strike
a
key, the higher
the voltage pulse and the higher the volume.
This
effect
is
programmed
into
some
of the preset patches.
Similarly, the
INITIAL BRILLIANCE
lever [42]
applies the
key timing
pulse to the
VCF,
thus
raising
the
cutoff frequency
of both
filters.
This
increases the
amount
of high frequencies which can
pass
through
the
VCF
by an
amount
proportional
to the voltage of
the timing
pulse,
and only
for the duration of the
pulse.
Pressure Sensitivity
A
sensor beneath
the front of each key
is
used
for
the
AFTER
(pressure sensitive) effects.
The
harder
you
press
a
key
after
it
first
touches bottom, the
higher the voltage allowed
to get through
a variable
pad
in the key's sensor. Various
effects are
produced
by
the voltage,
depending on
how
the
presets, pro-
gramming, and
TOUCH
RESPONSE
sections are
set;
the keyboard's after voltage
is
applied to the control
input of the appropriate voltage controlled
circuits.
Keyboard
Control
The
keyboard
control
HIGH
and
LOW
levers affect
the upper and lower
portions
of
the keyboard
separately, with increasing effect toward
the
ends
of the keyboard. Thisis done
for
LEVEL
and
for
BRILLIANCE.
The
effect
is
actually achieved by
a
digital circuit
which
interprets the position of each
note played on
the
keyboard and produces
a
pro-
portional
amount
of dc
voltage.
With
the
HIGH
levers,
the higher the note, the higher the voltage. With
the
LOW
levers,
the lower the note, the higher the
voltage.
If a
BRILLIANCE
lever
is
engaged, the extra voltage
is
added
to the
VCF,
raising the cutoff point
for
a
more
brilliant
sound.
If
a
LEVEL
lever
is
engaged,
the
extra voltage
is
added
to the
VCA,
increasing the
volume
of the note.
(BRILLANCE
and
LEVEL
are
decreased by reversing the polarity of the keyboard
control
voltage.)
Portamento/Glissando
The
glissando effect
is
produced by
a
digital circuit
which "looks at" the
last
note played and
at the note
being played. Instead
of allowing the voltage fed to the
VCO
to
jump
instantly to the voltage called for by the
note being played, the
glissando
circuit
gradually
moves
the voltage
from
that of the previous note to the
currently played note.
A
digital circuit
causes the
voltage to increase or decrease
in
quantized increments
that correspond to half-step increments
(a
chromatic
scale).
The portamento
effect
is
actually
produced by
the
same
circuit
that produces
the glissando,
except
that an
additional circuit
element
is
added. This
element
"integrates" the steps of voltage,
smoothing
the
transi-
tion
from one
note to the next. Thus, the change
is
continuous
rather than stepped.
Ribbon
Controller
The
ribbon controller
is
a felt strip
beneath which
is
located
a flat resistive
pad and
a
conductive
cord.
When
you
press
down
on
the
felt,
the cord contacts
the pad
and
establishes
a
given
resistance.
Voltage
passes through the
pad and
the cord, the value varying
in
proportion
to
where the
strip
is
pressed
down. The
actual voltage
produced
when
the ribbon
is
first
pressed
down
is
not important;
it
serves only
as a
reference
point.
The output from
the ribbon
circuit
then
be-
comes
proportional to the difference between the
reference point and any
other point
touched on
the
ribbon.
A
comparator
circuit "looks at" the change
in
voltage
and produces
a
positive dc output
when
the
second
point touched on the ribbon
is
to the right of
the reference point.
A
negative
dc output
is
produced
when
the second
point
is
to the
left
of the reference
point.
The
further
away
the second point
from
the
reference point, the higher the voltage output
(positive or negative).
No
voltage
output
is
produced
if
only one point
is
touched.
It is
necessary to
move
a finger
along the
ribbon, or to
hold one
finger
in a
given point and
then
touch another
finger elsewhere on the ribbon
in
order
to achieve an
effect.
The
voltage output from
the
ribbon
controller
is
fed to the
main VCO's,
thus
changing
the pitch of any
note
or
notes being played;
a
positive voltage
would
raise
the
pitch,
and
a
negative voltage
would
lower
the
pitch.
Pitch Control
&
Detune
CH
il
Control
The
pitch control
adds
more
or
less
voltage to "bias"
the
VCO
control inputs, thus raising or
lowering the
frequency produced
when
a
given
key
is
depressed.
The
pitch control feeds both channels an equal
amount
of voltage.
The
coarse pitch control merely
produces
a greater range of voltage variation
than
the
fine pitch control.
The Detune
CH
II
control really
does
the
same
thing
as
the fine pitch control, but
it is
connected
only to channel
II.
Thus, only the pitch of
channel
1 1
changes.
Ring Modulator
A
Ring Modulator blends
two
signals
together
in a
special
way, "beating"
a
sub
oscillator against
whatever
input
signal
is
fed to the
modulator
input.
The
output
does not contain
the input
signal
frequency
(or
frequencies), but
it
does contain
what
are
known
as
sum and
difference frequencies.
Sum
and
difference
simply
means
that the sub
oscillator
frequency
is
added
to
the input frequency, and
is
also subtracted
from
the input frequency.
(Actually, the
mathematics
that describe the modulation
are
somewhat more
complex
because
two
times the sub
oscillator
fre-
quency
is
subtracted from and added
to the input,
three times the
sub
oscillator frequency,
etc.).
The
effect
may
resemble
"ringing," although the term
"ring
modulator"
is
believed to be derived from
the
configuration of the diodes which comprise such
modulators; they
are
wired
in a circle.
The
sub
oscillator
frequency
is
set with the
SPEED
lever,
and the
amount
of
sub
oscillator voltage fed to
the ring
modulator
is
set
with the
MODULATION
lever.
An
envelope generator
is
provided
for the
sub
oscillator,
and may
be used to change
the speed
when
a
note
is
played.
The
ATTACK
TIME
lever
and
DECAY
TIME
lever respectively
speed up and
slow
down
the
effect
from whatever speed
is
set
with the
SPEED
lever to
some
higher
value,
and back
to the
set
speed.
The amount
of
change
in
speed—
the
amount
of
envelope
voltage fed to the
sub
oscillator-is
set
with
the
DEPTH
lever.
Panels,
Memories
&
Preset Patches
The main programmable
panels provide
a
means
for
the player to adjust the
many VCO, VCF
and
VCA
characteristics,
as
well
as
touch
response
characteristics,
that together
comprise
a
basic "patch"
or
sound. The
memories
are miniaturized versions of the program-
ming
panels,
and
are
used
in
exactly the
same
v\/ay.
The
preset patches
(PRESET TONES)
were
all
derived
from
actual settings of the
main programmable
panels.
Once
a
given
patch was
derived, the resistance value or
switch
position of
each panel control
was measured.