Harman Kardon CD 401 - Cassette Tape Handling; Dolby C-Type NR System

® Be sure to remove the cassette tape from the cassette
compartment after the end of operation to keep the tape
quality and maintain the deck performance for a long
time.
® Store cassette tapes off from a strong magnetic field
such as near a TV set, amplifier and speakers to prevent
adverse effect on the recorded sound.
® Before a cassette tape is played back or recorded, be sure
to eliminate tape slackness. A slackened tape, if used,
may cause jamming in the tape running mechanism.
Remove tape slackness
by winding with a pencil.
® If the sound recorded on the tape is desired to be pro¬
tected from accidental erasure, remove the erase-preven¬
tion tabs. With these tabs broken out, accidental erasure
can be prevented even if the RECORD button is inadvert¬
ently pressed.
® If it is later desired to record on a cassette tape protected
in this way, cover the holes with adhesive tape.
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 8-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 re¬
cords or FM radio that contain a lot of noise, i.e., it is
important to choose signals with as little 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 site of magnetic particles on the tape. Hiss
noises decrease if the magnetic particles are small, and also
decreases if the tape is played at a higher speed. In other
words, the high speed of the tape playing, and the small
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, will 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 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 accord¬
ingly, as the signals become smaller. Noise reduction is
achieved in this way.
While the Doiby B-Type NR System has only the noise re¬
duction capacity of the noise ievel 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 Doiby C-Type NR System assures enough
dynamic range and SN ratio to record a Hi-Fi program
source.