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When recordings are made at the same recording level and by
using different brands of tape, even though the type of tape
(regular or "normal" tape, for example) is used, when these
recordings are played back the listener may notice that the
high-frequency sounds are not as distinct on one tape or the other,
etc.
The reason that such differences may be noticed is because there
are difterences of the frequency response (particularly in the treble
range) between cassette tapes of the various manufacturers of
taoe.
Although, for recordings and playback in which a noise-reduction
system is used, it is the principle for such recordings that the
recording and playback processes be at the same recording level,
if, as a result of the reason described above, there is a difference of
the frequency response, there will result a difference in the
processes for recording and for playback, and correct recordings
and playback cannot be accomplished.
In order to overcome this problem, this unit includes a bias-
adjustment control (for compensation of the frequency response)
so that the most appropriate recording can be made.
During recording
I
I
Make a recording as explained in steps 1 through 11 ot
"Recording". (Refer to page 10.)
Z
While then swltching back and forth between the original
sound source and the recorded tape by using the input
selectol on the connected amplifler, adjust (by using the
bias-adjustment control) so that the treble tone quality is
the same for both.
When making this adjustment it may be helpful to use as a
reference the changes made (by the bias-adjustment control)
of the between-station noise heard on the FM band. Also note
that the adjustment can be made more precisely by listening
through headphones while making the adjustment. Connect
the headphones to the headphones jack of the amplifier.
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Bias.becom.es.
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shal lower; the treble
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the treble characteristic
characteristic
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decreases.
increases.
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bias adiust
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After repeating the above steps if necessary, rewind the
tape and then begin the recording once again.
Notes:
oWhen metal-coated tape is used, there is almost no difference of
the bias characteristics, so there is no necessity to make the bias
adjustment (compensation of the frequency response). (No
adiustment can be made.)
.The adjustments for the bias does not need to be made again so
long as you continue to use the same type and brand of tape that
was used when these adjustments are first made.
Because the pilot signals, etc. included with FM stereo broadcast
signals are subjected to Dolby noise-reduction
processing in the
same way as the music signals when an FM stereo broadcast is
being recorded, there is apt to be deterioration of the tone quality,
and the noise-reduction effect is reduced.
This unit, however, is provided with an MPX filter that filters out the
19 kHz frequency, which is the frequency of the pilot signal.
Note that there is virtually no audible effect upon the tone quality as
a result of the use of the MPX filter.
This switch can be used during the recordlng of an FM stereo
broadcast that employs Dolby noise reduction so as to
prevent misoperation of the Dolby noase reduction.
This switch, however, should be switched OFF when a sound
source other than the FM broadcast is being recorded, such
as, for example, a sound source that has a wide frequency
range, such as a compact disc, etc.
Pllot signal
The pilot signal is a signal that is used to separate FM broadcast
signals in stereo (left and right channels); this signal is generated
on a frequency that is very close lo the 19 kHz music band.
The recording-equalizer
amplifier is an amplifier for supplying (to
the head) the current necessary for recording. Usually, loads such
as the recording head and bias trap circuitry (circuitry for control of
the bias current) would be applied to the output of this amplifier,
with the result that complex changes of the current phase occur,
causing distortion of the recording signal.
The recording-equalizer
amplifier used in this unit, however, is a
linear magne-field class M amplifier that is a combination of
class A voltage-control
amplifier circuitry and current-drive ampli-
fier circuitry. (See the figure below.) As a result, a current flow that
is equivalent to the current flowing in the pure resistance of the
current-drive amplifier can be supplied to the recording head.
Consequently, a magnetic field that corresponds to the input
signals is produced at the head and is recorded on the tape, which
means that recorded sounds are faithful to the original sound
source, without fluctuations of the current phase.
(dB)
+3
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Adjusting the bias currenl
compensated.
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, the high{requen
:y range rs
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20
200
1
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2 0 K
Frequency (Hz)
CLASS A VOLTAGE CURRENT DRIVE AMP
CONTROLAMp U-lCONV.)
Pure resistance
Current flowing through the current-drive amplifier's pure
resistance and current flowing through the recording
head become equivalenl.
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