Field of the Invention
This invention relates to a moving-coil type pickup cartridge that extracts a signal from a 45-45 stereo record, and particularly to a moving-coil type stereo pickup cartridge capable of obtaining a high productivity and a uniform quality by utilizing a generating coil with a simple shape and, and further, reducing crosstalk between right and left output signals.
Description of the Related Art
An iron-core type and an air-core type, roughly divided, have been proposed as moving-coil type stereo pickup cartridges (hereinafter, also referred to simply as MC cartridges).
The iron-core type MC cartridge, which is the former, has a representative one that is called Ortofon type in which a ferromagnetic body is used as a winding core of a generating coil referred to as an armature. Accordingly, the iron-core type has a characteristic that generation efficiency of a signal is favorable, and thus, has been employed in the majority of the MC cartridge.
On the other hand, the air-core type MC cartridge, which is the latter, has a technical problem that the generation efficiency of the signal is low, but a reproduced signal thereof is hardly influenced by magnetostriction (hysteresis distortion) caused by a ferromagnetic body to be employed in the iron-core type described above.
Accordingly, the air-core type MC cartridge is said to be capable of obtaining a more straightforward reproduced sound without any quirk in tone of the reproduced sound, and thus, there is a deep-seated popularity among enthusiasts.
In a power generation mechanism of the moving-coil type pickup cartridge described above, a record signal is picked up by a stylus, a generating coil in a magnetic circuit is vibrated by a cantilever so that a signal voltage is output to both end portions of the generating coil as it is well-known.
However, there is a technical problem that deflection of the cantilever or distortion by moment is caused to impair a sound quality due to the power generation using the cantilever. Further, the generating coil is disposed in a root portion of the cantilever, and thus, an amplitude operation of the generating coil is smaller than amplitude of a sound track engraved on a record, and accordingly, the generation efficiency is extremely low.
Thus, an MC cartridge, which is the air-core type MC cartridge and in which a generating coil is disposed in the middle of a cantilever to improve generation efficiency without impairing a sound quality has been proposed, and such a proposal is disclosed in U.S. Pat. No. 4,374,433 (Patent Literature 1), JP 52-10105 A (Patent Literature 2), JP 51-14002 A (Patent Literature 3), JP 51-34406 U (Patent Literature 4), or the like.
Meanwhile, it is desirable that such a type of MC cartridge have an extremely low impedance of the generating coil serving as a source to generate a signal and be capable of obtaining high output. It is said that it is possible to provide each requirement such as a wide dynamic range, high transient value, low distortion or a high S/N ratio when the above-described conditions are prepared.
With respect to this, an MC cartridge disclosed in Patent Literature 1 described above employs a configuration in which printed coils each of which is formed in an octagonal shape are used as generating coils. According to such a configuration, an impedance of the generating coil serving as a signal source is large while an effective mass as the generating coil is small, and as a result thereof, it is difficult to prepare the requirements described above as the MC cartridge.
In addition, an MC cartridge disclosed in Patent Literature 2 described above employs a configuration in which right and left generating coils, each of which has a triangular shape with rounded angles (so-called Japanese rice ball type), are attached to both opposing end portions of an armature which is formed in a pantograph and connected to a cantilever.
According to such a configuration, it is difficult to produce a delicate mechanism of the pantograph-like armature and the generating coil of the so-called Japanese rice ball type, and thus, it is difficult to obtain the MC cartridge having a high productivity and a uniform quality.
Further, an MC cartridge disclosed in Patent Literatures 3 and 4 described above employs a configuration in which a generating coil of one channel and a generating coil of the other channel are wound while being superimposed on each other to cross each other in a grid pattern.
According to such a configuration, the generating coils are wound while being superimposed on each other in the grid pattern using a quadrilateral winding frame, and thus, a winding operation of the right and left generating coils is complicated and not easy. Accordingly, similarly, it is difficult to obtain the MC cartridge having a high productivity and a uniform quality.