Harman Kardon CD191 Owners Manual - Page 4

Principle, Function, Dolby, Noise, Reduction

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Dolby C-Type NR System Your deck provides the Dolby C-Type Noise Reduction system, which is said to be the ultimate in noise reduction system. Also, you can work the standard Dolby B-Type Noise Reduction System by changing the B-C select switch. The Dolby NR System is one of the methods for reducing the noise that is created during the play back of a tape, and is now widely and internationally used. The noise which this system reduces largely emits from the tape itself and this system cannot reduce the noise which comes from the program which is being recorded. Therefore, in order for the Dolby NR System to function more effectively, it is important to avoid recording from signals either from records or FM radio that contain a lot of noise, i.e., it is important to choose signals with as l ittle noise as possible. Principle Any magnetic tape used on a tape recorder contains native noise. In particular, among these noises, the middle and high frequency noises, which we can easily pick up by hearing, are called "hiss noises", and they are said to be caused by the size of magnetic particles on the tape. Hiss noises decrease if the magnetic particles are smal l , and also decreases if the tape is played at a higher speed. In other words, the high speed of the tape playing, and the smal l size of the magnetic particles produce the same effect as regards the hiss noise. In this respect a cassette tape played at a low speed, wil l produce more hiss noise. Function of the Dolby Noise Reduction When the recording input signals are lower than the standard level, those middle and high frequency sounds among those signals are gradually strengthened and recorded. The signals will return to the original state if a tape is played back opposite to the way it was recorded, i.e., if it is played back with middle and high frequency sounds above the standard level being gradually weakened. At the same time tape hiss sounds, which are middle and high frequency noises, created during the play back are reduced accordingly, as the signals become smaller. Noise reduction is achieved in this way. While the Dolby B-Type NR System has only the noise reduction capacity of the noise level of 10 dB, the Dolby CType NR System has a capacity of 20 dB. This C-Type NR System, in comparison, has an improvement in its function in the high frequency range so that it can be used for 0 dB recording. The Dolby C-Type NR System assures enough dynamic range and SN ratio to record a HI-FI program 'source. 50 40 30 (dB) 20 B Type 10 0 20 c Type 50 100 200 500 1000 2000 5000 10000 20000 (Hz) NOISE SPECTRA 3

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Dolby
C
-Type
NR
System
Your
deck
provides
the
Dolby
C
-Type
Noise
Reduction
system,
which
is
said
to
be
the
ultimate
in
noise
reduction
system.
Also,
you
can
work
the
standard
Dolby
B
-Type
Noise
Reduction
System
by
changing
the
B
-C
select
switch.
The
Dolby
NR
System
is
one
of
the
methods
for
reducing
the
noise
that
is
created
during
the
play
back
of
a
tape,
and
is
now
widely
and
international
ly
used.
The
noise
which
this
system
reduces
largely
emits
from
the
tape
itself
and
this
system
cannot
reduce
the
noise
which
comes
from
the
program
which
is
being
recorded.
Therefore,
in
order
for
the
Dolby
NR
System
to
function
more
effectively,
it
is
important
to
avoid
recording
from
signals
either
from
re-
cords
or
FM
radio
that
contain
a
lot
of
noise,
i.e.,
it
is
important
to
choose
signals
with
as
l
ittle
noise
as
possible.
Principle
Any
magnetic
tape
used
on
a
tape
recorder
contains
native
noise.
In
particular,
among
these
noises,
the
middle
and
high
frequency
noises,
which
we
can
easily
pick
up
by
hearing,
are
called
"hiss
noises",
and
they
are
said
to
be
caused
by
the
size
of
magnetic
particles
on
the
tape.
Hiss
noises
decrease
if
the
magnetic
particles
are
smal
l
,
and
also
decreases
if
the
tape
is
played
at
a
higher
speed.
In
other
words,
the
high
speed
of
the
tape
playing,
and
the
smal
l
size
of
the
magnetic
particles
produce
the
same
effect
as
regards
the
hiss
noise.
In
this
respect
a
cassette
tape
played
at
a
low
speed,
wi
l l
produce
more
hiss
noise.
Function
of
the
Dolby
Noise
Reduction
When
the
recording
input
signals
are
lower
than
the
stan-
dard
level,
those
middle
and
high
frequency
sounds
among
those
signals
are
gradual
ly
strengthened
and
recorded.
The
signals
will
return
to
the
original
state
if
a
tape
is
played
back
opposite
to
the
way
it
was
recorded,
i.e.,
if
it
is
played
back
with
middle
and
high
frequency
sounds
above
the
standard
level
being
gradual
ly
weakened.
At
the
same
time
tape
hiss
sounds,
which
are
middle
and
high
frequency
noises,
created
during
the
play
back
are
reduced
accord-
ingly,
as
the
signals
become
smaller.
Noise
reduction
is
achieved
in
this
way.
Whi
le
the
Dolby
B
-Type
NR
System
has
only
the
noise
re-
duction
capacity
of
the
noise
level
of
10
dB,
the
Dolby
C
-
Type
NR
System
has
a
capacity
of
20
dB.
This
C
-Type
NR
System,
in
comparison,
has
an
improvement
in
its
function
in
the
high
frequency
range
so
that
it
can
be
used
for
0
dB
recording.
The
Dolby
C
-Type
NR
System
assures
enough
dynamic
range
and
SN
ratio
to
record
a
HI-FI
program
'source.
50
40
30
(dB)
20
10
B
Type
c
Type
0
20
50
100
200
500
1000
2000
5000
10000
20000
(Hz)
NOISE
SPECTRA
3