JVC DD-9 A - Three-head System; Description on New Technology; DD (Direct Drive) Mechanism; All-stage DC Configurated Amplifiers

DD-9A/B/C/E/J/U |
Description on New Technology
= DD (Direct Drive) Mechanism Equipped with Newly = Memory Stop and Auto-rewind
Developed Quartz-locked Pulse Servo DD Motor
A direct drive system is employed in which the motor
shaft itself is the capstan shaft, without the rotation
transmitting members (idlers, pulleys, etc.) which cause
unstable tape rotation. Our newly developed pulse servo
motor is employed for this driving power source.
The motor’s construction is free from thrust unbalance
or cogging, thus permitting a high flywheel effect. For
precise rotation, this motor uses a full-circumference
integration type FG detection system and an auto-
balance circuit which reduces torque unbalance. Thus,
the motor drives the tape transport mechanism with
smooth rotation. Further, the employment of the quartz
lock system results in exceedingly small fluctuation of
speed.
For detailed information, refer to service manual (No.
4195)for DD-7.
Three-head System with X-cut SA Record/Playback
Combination Head
The record head uses a 4u-gap SA head for improved
recording sensitivity and a reduced distortion rate. The
playback head uses an X-cut 1p-gap SA head for reduced
low-frequency contour effect. These two heads are com-
bined. The erase head employs a 2-gap SA head excellent
in erasure efficiency. For more details, refer to page 5 in
service manual (No. 4186) for KD-A77.
All-stage DC Configurated Amplifiers
The playback head and the equalizer amplifier are direct-
ly coupled. Since all stages between amplifiers are DC
configured, the number of the capacitors which adversely
affect sound quality, is decreased. In addition, the +2 V
constant voltage source and the differential amplifier
enable stable high linearity and wide-band reproduction.
Dot-matrix Type 2-color FL (fluorescent tube) Peak
Level Meter
The 2-color fluorescent indicator tube which is longest
at 135 mm among cassette decks. The R and L indicator
bars are independent of each other. Each bar is divided
into 18 segments, each further into 20 dots. So, the level
can be monitored with a feeling of a consecutive bar
graph.
This meter is provided with a peak-hold function, thus
facilitating level setting. Moreover, it has a selection
switch between the PEAK and VU meters.
No. 4198
By joint use of the MEMORY switch, AUTO REWIND
switch (PLAY/STOP) and the electronic counter, the
following operations are possible:
Continuous tune repeat between the beginning of the
tape and the point of the tape at which the MEMORY
switch is pressed; tune repeat between ‘000’ to which
the counter is reset by the RESET switch and the point
of the tape at which the MEMORY switch is pressed or
between this pcint of the tape and the end of the tape.
Needless to say, the conventional functions can be per-
formed by ON-OFF operation of the MEMORY switch
or the AUTO-REWIND switch (ON/OFF) singly.
Electronic Volume Control
Motor rotation is controlled by switching the polarity
by IC so that the input volume can be set by one-touch
recording level UP-DOWN operation.
The set recording tevel is indicated by the needle which
moves in response to the control motor.
Newly Developed Computer B.E.S.T. (Bias Equalizer
Sensitivity Tuning) System 3-head Tape Deck
This system was developed for 3-head tape deck utilliz-
ing the fundamental concept of the previous versions
KD-A8 and KD-A66.
With stress laid upon MOL balance, the bias leve! is set
at the average of the optimum bias points which are
detected at 16 steps each for R and L channels.
To control the medium-frequency response, a process
to make the 4 kHz/1 kHz response flat is provided. This
response is set at the average between those R and L
values which are taken each at 8 steps.
The tape sensitivity is set at an average of those R and
L values which are taken at 16 steps each. The high-
frequency equalization level is adjusted at 16 steps each
for R and L channels, independently.
In addition, since the A/D conversion system of the
detection signal has been changed from the peak-hold
type to the soft peak-hold type, a momentary pulse
due to noise is not detected. Therefore, this system is
designed to hold nothing but continuous sigrals.