Handling And Care Of The Compact Disc - Revox B225 Operating Instructions Manual

1.3.2
Handling and care of
the compact disc
Handling of the compact disc
is
more convenient and trouble-
free
than
is
the case
with
LP
records.
However,
it is
still essential
to
observe certain precautions
which can
be better
followed
if
the
mechanical design of the compact disc
is understood.
The
compact disc
consists of three layers.
A
relatively strong
transparent substrate
is
coated with
an
ultrathin aluminized lay-
er on
which the information
is
encoded.
The label
(content, art-
ists,
disc brand)
is
printed
on
this sensitive
layer.
Thevarnish
and
the
ink
applied during the printing process
are
the only protec-
tion of the aluminized
layer.
Although the
laser
pickup "reads"
from
the
opposite
side.
which
is
the
much
better
protected
side,
a
scratch on the
printed
side
of
the
aluminized
layer can
interfere
with
or even
prevent playback
of
the compact disc. The
pitch of
the information "grooves"
on
the compact disc is only
1.6pm
and the average bit length
is
approximately'1 pm
(:'111000th
of
a
millimeter).
ln
view
of
these microdimensions
it becomes clear
that
a
scratch
on
the printed
side of
the compact disc can
have
disasterous consequences.
On
the read side (scintillating surface),
a scratch or
fingerprint
has little or no effect. This side is largely
protected
by
the
strong
substrate. The laser
pickup
is
not
easily
confused
by
scratches
and contaminations.
Because
of the strong focussing,
dirt par-
ticles on
the
CD surface cause little interference.
Despite
this. compact discs should be
handled
carefully
and
kept clean
in
the same
way
the
hi-f
i
enthusiast
is
accustomed to
from
LP records.
Cleaning of
the compact disc
is
not necessary
if
the
CD is
only
touched
along
the
edges
and
if it is
immediately returned
to the
origina
I
jacket
after
it
has been used. Dirty compact discs can
be
cleaned
with
a lint-free, soft piece of cloth. Never
use
any sol-
vent or abrasive cleaning
agents.
,l:
s
*
1.3.3
Structure
of
the compact
disc
A great abundance of information
is stored on
a
compact
disc
The user gains full advantage
of
the possibilities offered
by the
CD system only if he knows the structure
of
the compact
disc.
The
maximum playing time of
a
compact disc
is
approximately
70
minutes. This makes it
possible, for
example,
to play
Iong
concerts without interruption.
However, because
it
is
frequently
desired to search and play individual
passages,
corresponding
information must also
be
encoded
on
the audio track.
The
fol-
lowing
methods are used on the compact
disc.
-
lf the content can be subdivided into individual
selections.
these
are
separated
by
short silent grooves.
On
the
compact
disc these selections are identified
as TRACK
-
A different method of subdividing
is
the
use
of
indices
(lN-
DEX). Classrcal recordings in
which most works consist
of
movements
are
provided with
indices
by
some
of
the disc ma
n
ufactu
rers.
Note:
The
subdivision
of
compact
discs
is def
ined bythe
CD
manufac-
turer. On recordings comprising severai sections
for which
no
indices
have been created. the starting time (CD-TIME)
is usual-
ly specified on the jacket.
-
Each
compact disc
is also subdivlded into minutes and
se-
conds
of play time.
Any location
can,
therefore,
be
accurately
and reproducibly accessed
The
time indicated
on
the display
of
the
REVOX
8225
ts
always
read
f
rom the
compact
disc and
does not correspond to the actual playing time
of
the
unit. Of
course,
any location can
be searched
in TRACK TIME as
well
as in
CD
TIME
mode
(refer to
Section 2.3 "Caution").