Maintenance - NAD 613 Owner's Manual

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level will result in excessive tape hiss, whereas too
high a recording level will result in distortion. The
standard procedure is to set the recording level to
accommodate the loudest part of the music, and then
leave the controls alone. Set the control so that sus-
tained sounds, e.g. a singing voice or full orchestral
chord reaches the red segments (up to 4 dB). With
music that spans a wide range of volume levels, this
may mean that the quiet portions of the music will be
recorded at a level of -20 dB or less (with no seg-
ments illuminated). This is normal.
The BALANCE (13) control will allow you to alter
the left/right balance of a recording. When turned fully
counter clock-wise, only the left channel will be
recorded, whereas turned fully clock-wise only the
right channel will be recorded. For normal use the
control is set in the detent in the centre of its range,
recording each channel with equal levels.
If you wish to erase a tape, without making a new
recording, follow the procedure as described above,
but turn the RECORD LEVEL (12) control fully
counter clock-wise. No recording level segments will
illuminate.
ACCIDENTAL ERASURE PREVENTION.
Whilst making a new recording any previous
recordings already on the tape will automatically be
erased. If you wish to protect a tape from being
erased or re-recorded accidentally, you can remove
the tape's protection tabs. This way the record func-
tion will not engage. Please note that most pre-
recorded tapes commercially available already have
the tabs removed. Using adhesive tape over the
holes will enable the circuits to record again.
CrO2 (type II) and Metal (type IV) tapes have addi-
tional holes in the cassette housing, enabling the
deck to "recognize" the various tape types. Make sure
you do not cover these holes as well! Refer to figure
3.
THE PLAY TRIM CONTROL.
Position the PLAY TRIM control in the "0" (centre
detent) position for normal play-back.
Errors in high frequency response often occur in
cassette recordings, especially in tapes that were
recorded on one machine and are being played on
another. These errors arise from tape saturation -
particularly those tapes recorded on decks without
HX Pro headroom extension -, from biasing that didn't
match the tape when the recording was made, and
from differences in equalisation and head azimuth
among recorders.
These errors cause mis-tracking of the Dolby NR
circuits, which in turn cause the faults to be "magni-
fied" by the circuits, often resulting in dull sound.
Play Trim is a special high-frequency play-back
equalisation circuit, used to restore accurate play-
back response before Dolby NR decoding takes
place. Standard play-back equalisation, for correctly
recorded tapes, is provided when the Play Trim con-
trol is set at the detent in the centre of its range.
When playing tapes, set the DOLBY NR selector to
NAD
8
match the recorded tape. If the recording sounds dull,
turn the Play-Trim up (clock-wise) to restore accurate
highs. If the recording sounds edgy or sibilant, turn
the Play-Trim down to obtain smoother treble.
NOTE: The Play Trim control only affects play-back
and doesn't function whilst making a recording.

MAINTENANCE

The bearings and other moving parts have been
factory treated with special lubricants and do not
need any special attention.
Dirt, dust and tape-oxide can potentially damage
the heads and tape guidance, besides degrading the
sound quality both on play-back and recording. Parts
in direct contact with the tape therefore need to be
cleaned regularly.
NOTE: Make sure the receiver or amplifier is
switched off before cleaning or demagnetising the
heads.
CLEANING
Open the cassette compartment door. At the bot-
tom of the compartment you can see the heads and
tape guidance (capstan and pinch-roller). Refer to
figure 4.
Clean the heads (A & B) and the capstan (C) using
cotton wool buds with pure alcohol or with a dedicat-
ed Tape Recorder Cleaner.
Clean the pinch-roller (D) using only distilled water.
Never use alcohol on the roller, as the rubber will dry
out. Alternatively, you can use a special cleaning cas-
sette. Be sure to use a cassette that cleans all parts
illustrated in figure 3.
DEMAGNETIZING
Parts in direct contact with the tape will become
slightly magnetic over time. This magnetism will
increase hiss, both during play-back and recording.
It is therefore advisable to demagnetise the heads,
pinch roller and other metal tape guidance parts from
time to time, using a demagnetiser or a demagnetis-
ing cassette. Follow the instructions of the demagne-
tiser or demagnetising cassette.
WARNING
Keep demagnetisers away from your tapes, they
can accidentally erase the recordings.
Your dealer will be able to advise you and supply
the proper accessories for both cleaning and demag-
netising.
PLAY TRIM was developed by NAD and Dolby Laboratories Inc.
HX Pro originated by Bang and Olufsen.
Dolby Noise reduction and HX Pro headroom extension manufac-
tured under license from Dolby Laboratories Licensing Corporation.
"Dolby" "Dolby NR", the double-D symbol and "HX Pro" are regis-
tered trademarks of the Dolby Licensing Corporation.
Dolby NR is a registered trademark of Dolby Laboratories Ltd.