Dual Discrete™ Optical Pickup; Servo Dsp Lsi; Rf Processor Lsi - Sony SCD-1 Technical Background

2.3. Dual Discrete™ Optical Pickup.
Compact Disc requires a laser wavelength of
780 nm. SACD uses 650 nm. Compact Disc
requires an objective lens numerical aperture
(NA) of 0.45. SACD requires 0.60. Instead of try-
ing to compromise these requirements, or switch
lenses or lasers, Sony employs two separate
optical pickups. One is dedicated to CD while
the other is optimized for SACD. So you get
ideal tracking for both types of disc.

2.4. Servo DSP LSI.

Super Audio Compact Disc has half the spacing
between tracks (track pitch) of CD. The pits
themselves are also half as long. As a result,
SACD requires absolute precision in playback.
That's why the SCD-1 and SCD-777ES employ
an exclusive Sony Digital Signal Processor (DSP)
to control spindle motor, tracking and focus ser-
vos. The DSP maintains superb precision for
extremely stable signal readout.

2.5. RF Processor LSI.

As the optical pickup reads the disc signals,
an RF amp located inside the mechanical block
amplifies them. This amplified RF signal is sent
to the RF processor, located on the main
circuit board.
The RF processor chip is responsible for clock
signal extraction, synchronization, demodulation
and error correction. Both the servo DSP and RF
processor are Sony Large-Scale Integrated (LSI)
circuits. Large Scale Integration makes for small-
er circuit boards—and reduced signal exposure
to hum and noise.
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