Pioneer PL-70

Commentary

A high-precision player system that realizes incommensurable stability by pursuing high precision and looks at the essence of the player to the ultimate.

For the drive part, we reviewed the bare characteristics of the rotation before applying servo, and developed and installed the SH rotor (Stable Hanging Rotor) method rotor) method to achieve rotational accuracy of orders of magnitude.
The SH-rotor system adopts a unique structure in which the rotor support point, which was previously located at the bottom of the motor, is moved just below the turntable. By this, the center of gravity of the turntable and the support point are almost matched.
This is achieved by a structure opposite to the conventional one in which a motor shaft is fixed, a ball bearing is mounted on it, and a rotor is rotated. This eliminates the unstable inverted cone motion caused by the coincidence of the supporting points.
The motor has a diameter of 31 cm and an inertial mass of 480kg-cm.²Equipped with a 2kg-cm high-torque DC servo motor that rotates the turntable at a constant speed within 1/3 rotation (approximately 1 second), it achieves excellent stability.

The turntable uses a low-pressure casting method different from the conventional turntable manufacturing method in order to obtain more stable rotation and excellent acoustic characteristics.
This is a hand-made method in which metal is slowly poured into an extremely precisely molded mold and cooled naturally over a long period of time. Since the inside of the mold is kept uniform with less soot and bubbles, it achieves higher density and better dynamic balance than conventional methods.
In addition, in order to deaden the resonance of the turntable itself, a special anti-vibration agent is applied to the back surface to prevent squealing which adversely affects the sound quality.

The magnetic pole switching mechanism of the motor uses a Hall element non-contact switching method developed by Pioneer.
The SH-rotor drive eliminates the fine noise that has been generated between the motor shaft and the bearing, and the special anti-vibration processing inside the phono motor unit realizes a high S / N ratio.

The arm base uses a 1 kg heavy weight arm base made of hand-made solid brass cut one by one. In addition, the support part that fixes the arm shaft uses a chucking joint system in which 8 metal blades clamp and tighten the entire face of the arm shaft evenly.
Unlike the general support system in which one point or several points are fixed with screws, this system eliminates play and prevents partial resonance. In addition, the chucking joint system is also adopted for the mounting part of the head shell to pursue sound quality by thoroughly eliminating resonance.

A newly developed realize high sensitivity while suppressing low-frequency resonance caused by eccentricity and warpage of commercially available records, a newly developed level variable oil braking system is adopted.
Silicone oil is injected into an oil cup installed in the arm bearing. A ring-shaped braking fin with the tip cut at 45 degrees is pinched to apply damping. The braking amount suitable for both vertical and horizontal directions can be applied at one point. This reduces the low-frequency resonance Q and flattens the mechanical impedance.
The level adjustment ring is free when the scale is 0, and the braking amount increases as the scale increases from 1 to 5. This design allows for a wide range of applications from the MC type, which has a relatively low compliance type, to the MM type, which has a high compliance. The level adjustment ring uses a helicoid type with a highly accurate lapping process to prevent partial resonance.

The tone arm part adopts a mass concentration system in which the main weight is brought closer to the arm shaft and the equivalent mass of the needle tip is reduced. By reducing the moment of inertia of the tone arm, basic performance before oil braking is also improved.
The bearing part of the tone arm utilizes Pioneer's precision pioneer's precision processing technology which boasts of micron order, and adopts stability support in which the pivot is stored in the pivot holder and supported by spring.
The tone arm is a long type design with an effective length of 282 mm using a high-rigidity aluminum pipe, and is equipped with a light-mass, high-rigidity carbon fiber head shell as standard.

The cabinet is a 8.5 kg heavy weight cabinet. This cabinet has a strong design consisting of four layers of conifer solid boards with high rigidity, high density and high internal loss, which were selected after trial manufacture and study of various materials.
In addition, the newly developed low-center-of-gravity insulator with spring support is used for the insulator, with the center of gravity of the player system and the supporting point of the insulator at approximately the same height.

Low-capacitance oxygen-free copper wires and gold-plated terminals are used to minimize transmission loss at the tone arm leads, power cords and their contacts.

It uses a purely electronic start / stop button.

5 mm thick smoke-degree acrylic hood made by hand craft is equipped as standard.

Uses a turntable sheet with excellent acoustic characteristics.

Model Rating

Type	Cartridgeless player system
Phono Motor Section
Model Name	MU-70
Motor	Quartz PLL DC servo Hall motor
Drive system	Direct drive
Bearing structure	SH / rotor system
Turntable Diameter	31cm
Turntable inertia mass	480kg-cm2(including turntable seats)
Number of revolutions	33 1/3, 45 rpm
Rotational speed change	Electronic with short stroke switch
Uneven rotation	0.009% or Less (WRMS/FG Direct Reading Method) 0.018% or Less (WRMS/JIS)
S/N	78 dB or more (DIN-B) 68 dB or More (JIS)
Load variation	0% (Needle Pressure 300g or Less)
Start-up characteristic	1/3 turn or less
Starting torque	2kg-cm
Speed detection method	All-round integration method FG
Rotational speed deviation	Not more than 0.002%
Drift	Time drift : 0.00008% / h Temperature drift : 0.00003% / ° C.
Brake mechanism	Pure electronic
Tone Arm Section
Model Name	PA-70
Type	Variable type oil braking system static balance S-shaped pipe arm
Effective length	282mm
Overhang	12.5mm
Tracking error	+ 1.8 °, -1.1 °
Needle pressure adjustment	Weight 1 Rotation 1g (0.1g scale)
Applicable Cartridge Dead Weight	4g ~ 24g (when using the attached shell)
Height adjustment range	+ / - 3 mm
Head shell	Carbon fiber head shell weight 7.6g
<General>
Attachment mechanism	Quartz lock indicator Quick stop
Semiconductors used	Quartz : 1 IC:6 Hall element : 3 LED:3 Transistor : 9 Diode : 4
Pwer	100 VAC, 50Hz/60Hz
Power consumption	9W
External dimensions	Width 550x Height 214x Depth 440 mm
Weight	23kg