Denon DRM-555 - Manual (Page 15)

ENGLISH
15
DOLBY B AND C NOISE REDUCTION SYSTEM
2 The Dolby noise reduction system substantially reduces the tape
background noise (hiss) inherent in the cassette medium. Dolby B NR is
most widely in use. However Dolby C NR is a much more recent
development and represents significant improvements over Dolby B NR.
2 Tape background noise consists primarily of high frequency information,
which is particularly annoying during soft passages. The Dolby NR system
increases the level of low volume mid- and high-frequency signals during
recording and reduces the level of these signals by an identical amount
during playback. As a result, the playback signal is identical to the original
source, but the level of background noise generated by the tape is greatly
reduced.
2 The operating principle of Dolby C NR is similar to that of Dolby B NR except
for the encoding/decoding response curves. The noise reduction effect
obtained with Dolby C NR is up to 20 dB, compared to 10 dB with Dolby B
NR. In addition, Dolby C NR uses an anti-saturation network and spectral
skewing circuitry for a significant improvement in the dynamic range of the
mid- to high-frequencies.
DOLBY HX-PRO HEADROOM EXTENSION SYSTEM
This deck is equipped with the Dolby HX-PRO headroom extension system.
Since the system functions automatically during recording, no switching
operation or adjustment is required. The system is effective with any type of
Normal, CrO
2 and Metal tape.
The Dolby HX-PRO headroom extension system functions during recording to
raise the saturation level in the treble range. Therefore, most of the treble
range components distorted or lost during recording on conventional cassette
decks are more faithfully recorded on the new DENON cassette deck.
Features of the Dolby HX-PRO Headroom Extension System
(1) Performance of Normal and CrO
2 tapes can be improved to very close of
that offered by Metal tape.
(2) The dynamics in the treble range are improved significantly.
(3) Since no decoding is necessary during playback, the improved sound can
be enjoyed on any type of tape deck, including portable players and car
audio systems.
(4) The system functions whether the Dolby B/C NR system is engaged or not.
MAINTENANCE
2 Head cleaning
After long usage, tape coating or dust may adhere to the heads, causing
deterioration of sound. Therefore, the parts depicted in the illustration
should be cleaned regularly. Use a cotton swab moistened with a tape head
cleaning solution (such as alcohol).
Notes:
1. Some cleaning cassettes on the market have a strong abrasive effects and
may scratch the heads. Always use cotton swabs instead of cleaning
cassettes.
2. Since the use of metal tape is apt to collect more dust on the heads, the
heads should be cleaned more often to enjoy the best possible sound.
2 Cleaning the Pinch Rollers and Capstans
If the pinch rollers or capstans accumulate dust, tape transport may become
unstable, as a result from slippage, during recording or playback. The tape
can also be damaged if it gets entangled in the capstan.
Clean these parts with a cotton swab or a soft cloth moistened with a tape
head cleaning solution (such as alcohol).
2 Demagnetizing the Heads
The heads will become magnetized after long usage or if strongly
magnetized objects are brought near them. The result is a generation of
noise, loss of the high frequency range, and in extreme cases erasure of
treble components on pre-recorded tapes in combination with added noise.
Thus, the heads should be demagnetized at regular intervals. (Head
demagnetizers are separately available from your dealer.)
2 How to Demagnetize the Tape Heads
1. Turn off the power.
2. Turn on the demagnetizer while it is at least 30 cm away from the
heads. Bring the demagnetizer near the heads and slowly move it in
small circles four or five times in front of each head, making sure you do
not touch them.
3. Slowly move the demagnetizer away and turn it off when it is at least 30
cm away from the heads.