Audio Database

The

Pioneer MU-61 28,500yen(around the 1972 time)
32,500yen(around the 1973 time)

Description
 
The belt drive phone motor which adopted DC servo hall motor.

The brushless motor to which Pioneer applied the hall device which developed the process is adopted as a motor.
The drive magnetic field of this motor is made by the electric current from the transistor circuit committed by switching of a hall device. The attraction-of-magnet transition to a hall device was regularly performed one by one by the magnet rotor magnetized beforehand, and has obtained the exact rotation.
Moreover, since it is a low-speed motor which rotates by a 10 times as much speed as a turntable, there is little oscillation and S/N and the endurance are improving.

Even if DC servo mechanism is carried and rotation deflection arises, a drive voltage is made to control and an exact rotation is maintained.
This servo mechanism consists of a capacitor type rotational frequency detector which does not receive the influence by a transition of ambient temperature, or the attraction of magnet of a rotor magnet, and an electronics control circuitry,The method detector of a capacitor changed the deflection of the rotational frequency into the transition of the frequency of oscillation as it was, and the electronics control circuitry has controlled the drive voltage according to the transition.

The pure electronic formula is adopted as a rotational frequency switching, and since need to hang a belt and it is not necessary to change it like before, there is no trouble resulting from a belt or its switching organization.
Moreover, 33 The fine-tune thumb which became independent to 1/3.45rpm each is carried, and the coordination of the rotational frequency is enabled by ±2% of within the limits.


Rating of a mode
Form Phone motor
Motor Brushless DC servo hall motor
Drive system Belt drive
Turntable Diameter aluminum alloy die-casting of 31cm (1.4kg)
Rotational frequency 33 1 / 3 or 45rpm, a fine-tune possible
Rotational frequency adjustable range Less than ±2%, an each rotational frequency independent coordination
Rotational frequency switching Electronic formula
Rotation unevenness 0.05% or less (WRMS)
S/N 55dB or more
An attached organization Rotational frequency fine-tune knob
Stroboscope
Level
The semiconductor used Transistor: 22 pieces
Diode: 15 pieces
IC: One piece
Hall device: Two pieces
Dimensions Width 317x height 133x depth of 353mm
Weight 6kg