Audio Database

DRAGON-CT
Commentary

A record player that takes measures against record eccentricity by means of an absolute center search mechanism.

In the DRAGON-CT, attention is paid to the eccentricity of the record board, and attention is paid to the deterioration of sound quality when the absolute center between the center hole of the record and the sound groove is shifted, and a unique absolute center search mechanism is installed.
When a record is off-center, the tone arm swings left and right by the amount of eccentricity, and the cantilever is largely twisted with respect to the sound groove of the micron unit. This causes the cantilever to trace out of its center of operation, causing a phase shift between the left and right channels, which impairs sound image localization, sound transparency, and sound field reproducibility.
The absolute center search mechanism detects the amount of eccentricity when the record is set, and moves the upper side of the double-structured turntable by the amount of eccentricity, so that the center of rotation of the turntable and the absolute center of the sound groove of the record match with high precision.

In the absolute route center search mechanism, the eccentricity is detected by the sensor arm.
When the start switch of the Absolute Center Search is pressed, the sensor arm is automatically lead-in to the final sound groove of the r-home electronic drive, and the amount of eccentricity is detected from the left-to-right vibration of the sensor arm due to eccentricity. At this time, the magnitude of the vibration of the sensor arm is optically detected, replaced by A/D converted, and the microcomputer calculates the average value to determine the amount of eccentricity.
Then, based on the data obtained from the sensor arm, the turntable is stopped with the sensor arm swung to the innermost position. At this time, the rotation angle is detected by the slit carved in the lower part of the circumference of the turntable, and the turntable stops with high precision.
When the turntable stops, the center search rod in the strobe housing is activated and comes into contact with the center search turntable and starts pushing it. The center search rod is in a straight line connecting the motor spindle and the needle tip of the sensor arm. The sensor arm moves outward by the pushing distance.
The adjustment is completed when the sensor arm has been moved outward by the amount of eccentricity. Then, the turntable starts rotating again, the sensor arm returns after confirming that the sensor arm is no longer swung, and the eccentricity correction is completed.

With the Absolute Center Search mechanism, the center hole of the record is slightly out of the normal setting position (nominal center), and the Absolute Center is set directly above the motor spindle. The corrected eccentricity is limited to 20 microns or less, but this value is such that the sound quality degradation due to eccentricity is not felt.

The turntable drive motor uses Nakamichi's unique super linear torque DD motor.
In order to prevent this problem, the Super Linear Torque DD motor employs a method in which the rotor magnet is specially magnetized so that the magnetic flux change from the S pole to the N pole becomes a sine wave. In addition, the current switching to the drive coil also becomes a sine wave, and two pairs of sine wave torques that are magnetically offset by 90 ° are superimposed. The resulting torque is Sin. flutter2Θ + cos2(θ + π / 2) = sin2Θ + cos2Θ = 1 and is always constant. As a result, smooth constant torque drive without cogging or uneven torque is realized in principle, and generation of flutter is suppressed from the root.

The servo circuit uses a quartz PLL and FG servo system to improve rotational accuracy.

Grease is injected into the small gap between the motor shaft and the bearing, and a special slit is provided in the shaft so that a uniform film surface is always formed by rotation.
As a result, the pressure to the bearing is uniform, and quiet rotation is obtained and durability is improved.

In the DRAGON-CT, flutter components are reduced by the super linear torque DD motor, so the turntable does not need to be extremely heavy. Therefore, the total weight of the combination of the main turntable made of aluminum die-cast, the center search turntable made of glass, and the rubber mat is 3.05 kg.
In addition, the main turntable and the center search turntable are closely connected with each other through an air layer of several microns. This air layer absorbs vibrations from each other, and the squeal of the turntable is kept very low.

It is equipped with a nominal center reset button. Press this button before executing the absolute center search to reset the center search turntable to the nominal center.

The tone arm employs a specially designed oil-dump-type high-rigidity straight-tone arm that focuses on the high-performance MC cartridge designed by Lomas High Complinus.

The arm pipe is made of brass with high rigidity to reduce the weight of the arm tip and increase the strength at the same time. This improves the ability to follow the delicate movement of the needle tip and prevents the occurrence of partial resonance caused by variations in the strength of the arm pipe.

The vertical bearing is designed so that the needle tip is always perpendicular to the sound groove even if the tone arm moves up and down due to the warping of the record.
In addition, a high-precision radial ball bearing has been adopted for the horizontal bearing to increase the initial motion sensitivity in the horizontal direction and to improve the dynamic balance of the tone arm.

The arm pipe is replaceable, and it can be used with various cartridges by adding the replacement tone arm pipe TA-100 as an option sold separately.
A chucking joint system is used to join the arm pipe and body.

The lead wire inside the pipe is made thicker, and the connector section is inserted with gold-plated split pins for surface contact as well as self-cleaning, minimizing the output loss of the cartridge.

It employs an oil dump system using silicon oil, which does not change over time, and improves separation and resonance characteristics by suppressing low-frequency resonance near 5 to 10 Hz.

By adopting a double suspension system and a double-structured cabinet, the effect of vibration is reduced.

The suspension part is a double suspension system combining rubber and spring insulators.
Rubber insulators absorb relatively high-frequency floor vibrations, while spring insulators begin to absorb vibrations at relatively low frequencies, and extremely steep vibration damping characteristics are obtained over a completely free range in total.
In addition, the topboard attached to the turntable and tone arm is floated by a slightly soft tuned spring insulator, which is damped by a rubber damper to quickly absorb unwanted vibrations of the spring itself.

A unique double structure has been adopted for the cabinet.
Unlike the cabinet of a general player, the DRAGON-CT is made of punching metal on all sides of the cabinet to prevent vibration of the cabinet by transmitting air vibration smoothly.
The top and bottom two boards are made of particle board with a thrust plate finish that has high internal loss and is hard to resonate. The top board is attached with an iron plate from the back side to ensure sufficient synthesis, and the main drive motor and tone arm are attached to this iron plate to ensure complete integration of their movements.

To prevent air vibrations picked up by the dust cover from being transmitted to the turntable and tone arm, the dust cover hinge is directly connected to the bottom board.

A semi-automatic system is used for the control part as long as it does not adversely affect the sound quality.

The tone arm is an auto-return system driven by an optical switch and a dedicated coreless linear motor. Queuing and cutting are also available from the front control panel.
The lifting and lowering of the arm is made smooth by the smooth arm elevator of oil dump system.
Equipped with pitch control function of ± 6%.

Needle pressure adjustment can be controlled by direct reading up to 3g in 0.1g steps.
The anti-skating mechanism is also separated from the tone arm for ease of configuration.

The mounting part of the rubber insulator also serves as a height adjustment mechanism, and the horizontal balance of the cabinet can be adjusted according to the installation location.

Gold plated pinjack output terminal is used for the output terminal.

The top and bottom boards have a black painted natural wood veneer finish.

Comes with a 500g dedicated disk stabilizer that reduces the warpage of the record and improves the adherence of the turntable.

Model Rating
Type Record player
Phono Motor Section
Drive system Direct drive
Drive motor QuartzPLL DC, brushless / slotless / coreless super linear torque motor
Number of revolutions 33 1/3, 45 rpm
Pitch control + / - 6% variable
Turntable Main : 31.0 cm aluminum die-cast, 18 mm thick, 1.4 kg
Center Search : 31.3 cm glass, 6 mm thick, 1.1 kg
Rubber mat : 30.3 cm rubber, 6 mm thick, 550g
Start-up characteristic 1 minute or less
Rotational speed deviation Outside of measurement limit (when quartz lock)
Time drift Outside of measurement limit (when quartz lock)
Wow flutter 0.008% (WTD RMS/FG direct reading method)
0.03% (WTD RMS, after center search)
Signal-to-noise ratio 78 dB or more (DIN-B)
Moment of inertia 380 kg / cm2
Tone Arm Section
Format Static Balance, Straight Arm Pipe Type
Built-in oil dump mechanism, replaceable arm pipe
Total Length 305mm
Effective length 237mm
Effective mass 14g (excluding cartridge)
Needle pressure variable range 0 ~ 3g
Compatible Cartridge Weight 4g ~ 11g
Cartridge exchange system Arm pipe replacement system (chucking joint system)
Offset Angle 21 ゜ 30'
Overhang 15mm
Tracking error + 2.5 ° ~ -1 °
Arm lifter Oil dump system
<General>
Pwer 100 VAC, 50Hz/60Hz
Power consumption 23W
External dimensions Width 546x Height 230x Depth 421 mm
Weight Approx. 20 kg
Attachment Dedicated Disc Stabilizer (500g)
Attachment Dedicated Disc Stabilizer (500g)
RCA cable (oxygen-free copper)
Sold Separately Replacement Arm Pipe TA-100 (¥ 12,000)