L D D Playback Circuit of CLD-900, N T S C L V / C D com
patible player (Service M a n u a l VRT-050)
The LDD sound signal is decoded by C D circuitry because
the L D D digital signal conforms t o the C D format. Fig. 4
shows the simplified route of digital sound signal in the
circuitry of CLD-900.
The reproduced R F composite signal is amplified in H E A D
A M P and P R E B (Preprocessing b o a r d ) . The signal is am
plified again and video and F M s o u n d signals are removed
by 1.75MHz L P F in L D D B ( L D D b o a r d ) . The filtered
P C M R F ( E F M ) signal is then de-emphasized by R22, R23
and C17 and goes to C D D M ( C D d e m o d u l a t o r b o a r d ) .
Hereafter the L D D digital signal is processed in the same
way as C D signal. Refer to C D System, Vol. 7.
Fig. 4 Block Diagram of Audio Signal Processing Circuit of CLD-900
S e r v o S y s t e m
T h e revolution of the LD-spindle-motor is controlled by
L D spindle servo system which synchronizes reproduced
H sync with a reference signal while C D system syn
chronizes reproduced frame sync with its reference signal.
T h e former system is m o r e accurate t h a n the latter.
The L D D frame sync should also synchronize with its refer
ence signal for correct sound reproduction. In the L D D
system, however, feeding the phase difference signal back
to the spindle m o t o r should be avoided to prevent the sig
nal from interferring the color signal.
T o maintain the synchronization when an L D D disc is
played, the phase difference A P C O (Automatic phase con
trol signal output) between the reference signal generated
in the player and the reproduced frame sync is applied from
Z7 (TC9178F-19(APCO), C D D M , to V C X O (voltage con
trolled X ' t a l oscillator), not to the spindle m o t o r . (Ref.
p 6 1 , SM VRT-050) The V C X O generates a clock signal for
controlling digital signal processing speed. The phase
difference signal controls the V C X O when L D D is played
and L D / C D signal becomes H . The pulse-width-modulated
A P C O signal is converted into voltage signal by Z5 2 / 2
( L P F ) . The jitter m a d e by disc eccentricity is suppressed
by Z12 ( L P F ) . Q8 turns on, and thus the A P C O controls
the V C X O . Refer t o Fig. 5
25
DISC
PICKUP
HEAD
AMP
PREB
LDDB
LPF
1.75MHz
LDD signal
DE-EMPHASIS
AMP
CD signal
AMP
EQUALIZER
CD RF
LDD RF
CDDM
ATC
SYNC SEPARATION
EFM DEMODULATION
CORRECTION
DIGITAL/ANALOG
CONVERTOR
DE-EMPHASIS
DE-EMPHASIS
LPF
LPF
L-CH OUT
R-CH OUT
AUDB
Analog
BPF
2.3MHz
BPF
2.8MHz
AUDIO DEMODULATOR
AGC
AUDIO DEMODULATOR
AGC
LPF
TRAP
WINDOW
COMP
FROM CONT
AUDIO L SQ
LPF
TRAP
WINDOW
COMP
FROM CONT
AUDIO R SQ
CX DECODER
LPF
4MHz
