Dolby Noise Reduction System - Nakamichi 700 Operating Instructions Manual

The Dolby Noise Reduction System
Your Nakamichi 700 incorporates the Dolby
Noise Reduction System (Under license from
Dolby Laboratories, Inc.), originally
developed to produce a master tape from
which to cut records wth a high
signal to noise ratio
Noise heard from a recorded cassette
primarily comprises tape noise and the noise
produced by the playback equalizer
amplifier of the cassette tape deck, and is
largely distributed over a 2KHz to 10KHz
range Such noise can be effectively reduced
by amplifying signals within this range at the
time of recording, then attenuating them in
playback, through a process as illustrated in
Fig. 1.
If this treatment is given to such signals
regardless of their strengths, however, strong
high frequency signals cannot be recorded.
So it is necessary to change the gain of this
special circuit with respect to the strength of
the high frequency signals
circuit makes this possible
For instance, if high frequency signals of
-40dB enter the Dolby circuit from input
terminals, it delivers signals of
recording on to the tape
high frequency signals of -30dB enter
the same circuit from the playback head
(Fig 2), it delivers signals of -40dB for
reproduction from the stereo amplifier Thus
input/output signals are attenuated by 10dB,
with equivalent reduction in the level of tape
noise and equalizer amplifier noise. The
circuit is designed so that it does not affect
signals of -5dB or greater
As is clear from the foregoing explanation,
the signal to noise ratio of sound improves
by about 10dB if it is recorded and
reproduced through the Dolby NR circuit,
enabling you to enjoy clean, transparent hi fi
The Dolby NR
stereo sound
and recordings made under it can be
reproduced by any cassette or reel-to reel
-30dB for tape decks equipped with the same system,
regardless of their makes
Conversely, if
This system is international,
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