Construction; Circuit Board Layout - Sony SCD-1 Technical Background

3. Construction.

3.1. Circuit Board Layout.

After paying such meticulous attention to the
composition, design and execution of each
circuit, Sony was equally careful in the physical
arrangement of circuits in the chassis.
The main circuit board—which includes the DSP
servo LSI, RF processing LSI and system control
—is positioned directly underneath the fixed
pickup drive assembly. This was a design chal-
lenge. For example, it required a hole in the cir-
cuit board to accommodate a support post. But
this configuration reduces signal runs from the
laser pickups, reducing exposure to possible
interference.
The main circuit board itself follows Sony's
"digital minimum" design, with key components
as closely concentrated as possible. To accom-
plish the goal, Sony designed the printed circuit
pattern in 4 layers. And then applied surface-mount
LSIs and small-scale chips on both sides of the
board. As a result, a phenomenal amount of
circuitry fits comfortably on a single, small board.
Concentrating the main circuit board and placing
it under the mechanism leaves ample space in
the chassis for the two circuits that need
"spreading out." The power supply and the audio
circuit board.
Since the audio circuit board includes so many
components that determine sound quality, Sony
paid extra attention to its layout and construc-
tion. This is a double-sided glass epoxy board
with a bus bar and symmetrical left/right layout.
The digital LSIs, including VC24, S-TACT and
Current Pulse D/A Converter, are all surface-
mount components. And they're all concentrated
near the front of the chassis, for minimum radia-
tion of digital noise. The analog buffer amp uses
integrated-lead discrete components. These are
widely spaced, for minimum mutual interference.
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Voltage for the analog stage is provided by a
discrete left and right power supply secondaries,
located directly on the audio circuit board.
Separate left and right 3-layer bus bars help
minimize power supply impedance. To optimize
grounding, the audio output terminals are con-
nected to the audio circuit board using a thick
copper plate.
SCD-1 Internal structure
SCD-1 Main circuit board (top)
SCD-1 Main circuit board (bottom)