Audio Database


Pioneer PLC-1700
80,000yen(around the 1973 time)

The arm-less player which adopted the brushless DC servo direct-drive hall motor.

The direct-drive phone motor adapting a hall device is adopted as a motor.
Instead of the brush which was indispensable to the conventional DC motor, Pioneer has applied the hole blocking which developed the process to the magnetic-field detection of a switching organization. The oscillation decreased compared with the DC motor which has a mechanical switching organization by this, and S/N and the endurance are improved.
33 [ and ] as the rotational frequency of a record with the same rotation of a motor itself the direct-drive which drives a turntable directly at 1/3.45rpm -- since a scheme, the middle deceleration mechanism leading to rotation unevenness did not exist at all, but has acquired the outstanding property.

A hall device is a kind of a semiconductor, is the crossbar thin film metals made from the N type Insb composition, and if it sends an electric current through two terminations and an attraction of magnet is applied to a quadrature, it will have changed the magnetism into the electricity using the "hall effect" which a voltage produces among other two terminations.
In Pioneer, the new process of a vacuum deposition method was developed, and till then, 30-50micro have improved the thinness which was a threshold to the thinness of 0.8micro, and has realized the cheap and small hall device.

In order to always control a rotation correctly, DC servo mechanism is carried.
The rotation is automatically controlled by the capacitor type oscillator which does not receive the influence by a transition of ambient temperature, and the attraction of magnet of a rotor magnet, and this control circuit maintains the stable rotational frequency.

The brake mechanism who stops a turntable at the moment is carried at the same time it turns OFF a power switch.

The pure electronic formula is adopted as a switching of a rotational frequency. Moreover, a fine tune of a velocity is possible, looking at the stroboscope minced by the perimeter of the turntable by ±4% of within the limits.
The blinking switchpoint is provided in the lamp which illuminates a stroboscope so that it can erase, when unnecessary.

The cabinet of the double structure which combined plywood with thickness of 30mm and the metal base is adopted as a cabinet. Kibe is rosewood native wood finish.

The large-sized thing is adopted as an insulator and the howling and the extraneous vibration are reduced.
Moreover, while a height can adjust freely and looks at the level of a panel, a coordination of the degree of level is possible.

It can be used being able to attach a favorite tone arm to an attached panel. Moreover, if a book jacket is removed, it can be used to 16 type arm.
This board serves as a desorption type which can be removed simply on six screws, and if an optional sub panel is used, it can exchange many kinds of arms easily.

The Servo

Rating of a mode
Form Arm-less player
Motor Brushless DC servo hall motor (18 very 36 slots)
Drive system Direct-drive
Turntable The product made from diameter aluminum alloy die-casting of 31cm (1.4kg)
Rotational frequency 33 1 / 3 or 45rpm
Rotational frequency adjustable range ±4%, an each rotational frequency independent coordination
Rotational frequency switching Electronic formula
Rotation unevenness 0.04% or less
S/N 60dB or more
The arm which can be attached 14 types, 16 type (a hood mounting is impossible)
An attached organization Rotational frequency fine-tune thumb
Outage brake
Large-sized insulator
The semiconductor used Transistor: 23 pieces
Diode: 15 pieces
IC: One piece
Hall device: Two pieces
Dimensions Width 570x height 187x depth of 434mm
Weight 15.6kg
Option Sub panel PP-307 (1,500yen)