Yamaha CS-50 Servicing Manual page 32

~ D-1.\ CONVERTFR
1. Lac
1
dnr Netwod: to Set Octave Voltage (Analog)
Tile :imdamental voltage (3 to 6V), wliich can be varied by the pitch control, is applied to the ladder network
comprising a number ot resistors connected so as to form a ladder and divided exponentially to provide the
resultant voltages to the inputs of D-A converter gate. The five voltage values correspond to octaves as shown in the
table below. When the pitch control is set at the mid-point, 4V is applied to the TU terminal and 440 Hz can be
obtained at note A
3 .
Terminal
I
OCT 4
!
OCT 3
OCT 2 OCT 1 OCTO
IC6--cs~l
i
(Cs-·C4")
(C ..
-C3~)
(C3-c2•) (Cz)
Oct. voltare
I
4V
~~-2v
____ : ·
lV
0.5V 0.25V
2. D-A Converter Circuit
for
Octave
The octave data consisting of 3 bits, Bl to
IfT,
is directly input to the D-A converter without being affected by the
GLISSANDO operation circuit when POR terminal is
Jt
"0". The octave data turns ON the gate to which the
octave voltage (analog) corresponding to the data is :q•phcC:, thus converting the octave data (digital) to octave
voltage (analog). Since the octave data are processed
OI~
tlw
l1a~is
of time-sharing, when plural keys up to four are
depressed, the corresponding gates are opened through
ti!ll\'
-;hann:~
to output the octave voltage. The order is the
same as that of depressing keys.
3. Analog-Voltage Set ladder Network for Note
The octave voltage output from the D-A converter is applied to the note lado<'I netwLwk as fundamental voltage. In
the note ladder network, the octave voltage is divided to establish the musicu!
lerval for 12 notes (C#, D, D#, ... ,
"/A
A#, B, C,) in an octave and the octave output is provided to the analog
gaL·
as in
'.:a>e
of octave voltage to be
1
f•
selected by 4-bit note data Nl to N4 and output. While the note data are also procc%cJ ,,n the time-sharing basis
sequentially, its timing is slowed by a factor of 9 in comparison to the master dock
</1
su that the subsequent
sample holding with an integrator is available.
4. Output Control Circuit
The analog key voltage corresponding to each key output through the time-sharing is allocated to channels
1
to 4.
®
When only a key is depressed, the same key data is output in all four channels consecutively.
• When two keys are depressed, the key
voltag~
for the first-pressed key is output in Chl, and that for the
second key is given in Ch2 to Ch4 consecutively.
111
Thus, the empty channels are always filled with the key voltage for the last-pressed key.
~B If 4 keys are depressed, four key voltages are output in Chl to Ch4 in the order of depressing.
*Refer to Example of Output on the preceding page.
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