Quartz-Locked Direct Drive Turntable with provision for mounting 2 tonearms (1978-80)
Quite frequently we encounter strong demand of audio buffs for a turntable which can use a long type tonearm or 2 tonearms.
Strange to say, however, there is no adequate one available on the marketplace.
To cater for such requirements, Luxman decided to develop an epoch-making turntable with provision for two tonearms, including a long one.
The Luxman PD444 is a direct drive quartz locked turntable, and its most outstanding feature is its ability to remove all kinds of external load variation thanks to our exclusive load free spindle system.
Additionally, the PD444 is made extremely resistant to howling and mechanical vibration by means of insulators of a 2-step brake system with the lowest resonant frequency, and an ultra heavy chassis of sandwich structure made from 2 thick iron plates and a high density chipboard.
Needless to say, all the necessary conditions for a high grade player are satisfied.
Load-Free Spindle Motor
Though basically quartz-locked direct drive system, a newly developped motor is employed to alleviate the load of the turntable platter applied to the bearing, which is named "Load-Free Spindle" system. The platter is made to float by offsetting most of its weight by repeling power of magnetics in the motor, which makes it possible to reduce the platter's weight on the bearing to about 1/5 of its actual value.
Even the best quartz-lock system is not a cure-all, and it is effective only in the suppression of external disturbing load variations ranging from DC to 1 Hz. To reduce those of relatively higher frequencies (5 - 10 Hz) that cannot be controlled by the quartz lock system, the flywheel effect of the platter must be utilized. The heavier the platter and consequently the larger its moment of inertia, the better.
But here arises a problem with respect to the life of the bearing. A prominent feature of this turntable lies in the beautiful solution of this problem. With the Load-Free Spindle system, the motor itself has the repelling power to float the turntable platter is made floating by an additional magnet device.
2 Step Brake Insulator
generally speaking with an insulator the lower the minimum resonance frequency (f₀) and the higher the sharpnes of resonance (Q), the better the cut-off characteristics. If "Q" is simply made higher, however, the turntable becomes unstable against vibrations of large amplitude in the vincity of "f₀". To cope with these incompatible factors, a new 2-step brake insulator was developed. The neoprene rubber supporting the shaft of the insulator works against vibrations of small amplitude which cause acoustic feedback, and good cut-off characteristics are procured. White to counter the vibrations of large amplitude effective are the spring and viscous brake of neoprene rubber with silicon grease are effective. In other words, both cut-off characteristics and stability of operation are made compatible.
Slim yet Ultra Heavy Chassis of Sandwich Structure
An unusually effective counter-measure against howling is hidden in the slim, compact appearance - an ultra heavy chassis of sandwich structure consisting of 2 pieces of 3,2 mm thick iron plate and a high-density chip board. The iron plate itself is heavy in weight but susceptible to resonance, and therefore a high-density chip board which absorbs resonance is inserted between 2 iron plates. Thus we realized an ideal solid and resonant-free chassis for a disc player.
Sliding Arm-base for Easy Replacement of Tonearm
precision arm-rails make it possible to instal any of your favorite tonearms with "one-touch" operation. It is constructed so as to fix the tonearm firmly at the optimum position by simple operation of a lever while sliding the arm-base in line with the over-hang gauge on the panel. The arm-base is made of die-cast zinc resistant to howling. Also a 5 mm thick extruded aluminium plate is employed as the arm panel in view of elegance at the surface and easy provision of various tonearms.
Platter Mat to Hold Disc Firmly
A platter mat fit for the shape of the disc is employed to ensure the closest possible contact between the mat and disc. The surface of the mat is specially treated to realize smoothness, and the mat is made of high-density rubber to damp the platter itself.
Acrylic plates of 4 mm thickness are put together to form a dust cover, which is resistant to howling and external vibration. Also the hinge for the dust cover is incorporated into the slim chassis to provide a compact appearance. A semi-free-stop type hinge is used so that the total weight of the dust cover is applied to the turntable when it is closed. This also helps improve anti-howling characteristics.
Phono Motor Section
Driving system: Direct drive
Motor: Crystal control, load-free spindle system, flat brushless DC servo motor
Platter: 300 mm (12") aluminium die-cast 2.5kg
Rotation: 33⅓ and 45 rpm
S/N ratio: no less than 75 dB
Wow and flutter: no more than 0.025% WRMS
Torque: 1 kg/cm
Temp. characteristics: below 0,00003% / C⁰
Turning accuracy: 0,002%
Acrylic Resin Cover: 4 mm thick (1,6") detachable with semi-free-stop hinge , 2,5 kg
Insulator: Low "f₀", 2-step brake type by means of spring, rubber and grease, height adjustable (range: 10 mm )
lock Indicator: Blue - 33⅓ rpm; Orange - 45 rpm
Arm Base: detachable, die-cast
Toneram Selector Switch: tonearm -1; tonearm -2 interchangeable
Power requirement: AC 120/220/ 240 V, 50/60 Hz
Power consumption: 16 W
Dimensions (W x H x D): 664 x 392 x 160 mm (26¼ x 63 x 154 inch)
Weight: 22 kg, (48,6 lbs) net