Technology; Overview - Sony SCD-1 Technical Background

2. Technology.

2.1. Overview.

When Compact Disc players were new, audio-
philes had to learn the new language of laser
pickups, digital filters, D/A converters and analog
output filters. SACD has a comparable language
all its own. But SACD players are also CD play-
ers. So there are two signal paths inside the
player. At some stages, SACD and CD signals
receive exactly the same treatment. At others,
there are dedicated circuits strictly for one type
of disc or the other. Here's a brief overview of
which stage does what.
1. Dual Discrete Optical pickup.
Incorporates two separate pickups, one
optimized for SACD, the other dedicated
to CD.
2. RF Processor. For both types of disc,
this circuit performs clock signal extrac-
tion, synchronization, demodulation and
error correction.
3. DSD Decoder. For SACD only.
Authenticates the SACD invisible water-
mark, separates text from music and
forms the left and right DSD pulse trains.
4. ACP System. For SACD only. Controls
the influence of switching distortion.
Fig. 1 Signal Flow within SCD-1
DISC
RF Amplifier
Super Audio
CD
Pickup
CD
Pickup
RF Amplifier
[ƒs = 44.1kHz]
2
64ƒs 1 bit
ACP & Digital Filter
DSD
ACP System
Decoder
RF
Processor
Digital
Filter
ƒs 16 bit
The SCD-1 and SCD-777ES incorporate circuitry to handle
both Compact Disc and Super Audio Compact Disc signals.
5. VC24 Digital Filter. For CD only. A
supremely advanced version of the famil-
iar 8x oversampling digital filter.
6. S-TACT System. For SACD and CD.
Suppresses time-base errors for jitter-free
performance.
7. Current Pulse D/A Converter. For
SACD and CD. Supremely accurate con-
version from 1-bit digital to analog.
8. Low Pass Filter. For SACD and CD. A
General Impedance Circuit (GIC) stage
for superb bandwidth and sound quality.
9. Buffer Amplifier. For SACD and CD.
Discrete output circuitry for maximum
signal integrity.
Curent Pulse
S-TACT D/A
Converter
Noise
Shaper
PLM Pulse &
Reference Clock
Generator
Buffer
Amplifier
I/ V
Low-Pass
Converter
Filter
ACP &
Digital Filter