Rear-Panel Connectors; The Compact Disc; Lnteresting Facts About The Compact Disc - Revox B225 Operating Instructions Manual

1.2.3 Rear-panel
connectors
[30] AUDIO OUTPUT FIXED Output
for
connecting an amplifier on which the
input sensitivity can be matched to the
level of the CD player (the REVOX8251
amplifier is ideally matched at the fac-
tory).
[31] AUDIO
OUTPUT VARIABLE Active
speakers or a
power amplifier, etc.
can
be connected directly to this output.
The
volume can be adjusted with
the
keys VOLUME
*
and
-
on the front
panel of the CD player
t32l AC POWER Power inlet (the
line vol-
tage selector setting can be checked
adjacent
to
it).
[33] REMOTE This connector allows:
a) defeating
the
lR
receivet
and
b) connecting a cable-type remote
control
device.
1.3
The compact disc
1.3.1
lnteresting facts about the compact disc
The 5 km long
information "groove"
of
a
compact disc contains
a
complex digital signal: interleaved digital
values
from two
au
dio channels represent
the music
information.
Auxiiiary infor-
mation for indicating the selections (TRACKs),
playing
time. etc.
is
also stored
in
this information
"grove". The
information
on
the
compact disc
is
encoded on an ultrathin aluminized
layer.
The
digital information on this
layer is represented by "pits"
which
are
scanned
by a
laser beam. The reflection
of
the
laser
beam
is
converted simultaneously
by
several
photo diodes (light receiv-
ers)
into electrical (digital) signals
The aggregate signal output
by
the
photo diodes
is
processed
in
several steps. detection and
separation
of the
synchronization information, separation
of the
music and information data (e,9. TRACK TIME), generating
a
control signal
from the
synchronization frequency
and
the
quartz reference for controlling the platter
speed,
and convert-
ing the digital
audio signals
to their
originally analog shape.
Discrepancies between the digital audio signals and the error
detection
data
d
iscovered
du
ring the decoding
indicate that the
compact disc is defective. Signals that
still appear in
a
slighly
ir
regular
cycle
of
the
compact
disc
are
brought into
a
perfecttime
slot
pattern. Single errors
can
be corrected, uncorrectable
er-
rors are replaced
by
interpolation (mean values
from the scan-
ning
f
unction
before or after the error. lf uncorrecta
ble
errors
oc-
cur
in long bursts. the output
will
be muted softly
Pigit6l, eonvCision
Servo system
foi
track
.
alignment
{radial)
Display
To HiFi-
equlpment
[.eft
channel
Serro syslgm
,lai',
.
.iq.quisli'rg
.
,
,(vditical)'
l
Servo system.
-
..for
'
rotational
speed
To
HiFi-
equipment
Right channel
Laser beam refldcted
by,.disc
Photodetectors
Light >
electrical signal'
Demodulator
Electrical signal
>
data
Error correction
Possible
error
bursts
>
error-free
digital signal
D/A
conversion
Error-free digital
signal
> two
analog
audio (sound)
signal