Connector for condenser microphone
A 3-pin type output connector for a condenser microphone includes a grounding first pin and second and third pins for signals, provided on a connector base made of an electric insulator. Each pin contains a chip type inductor element that inhibits a high-frequency current, and includes a pin main body provided on the connector base, a cylindrical chip holder made of an electric insulator and having one end attached to an end of the pin main body located inside the microphone case, and a metal cap that covers the other end of the chip holder so as to be electrically insulated from the pin main body. The chip type inductor element is placed in the chip holder, and the pin main body and the cap are electrically connected via the chip type inductor element.
A microphone unit of a condenser microphone has a very high impedance and thus contains an impedance converter such as an FET (Field Effect Transistor) or a vacuum tube. Normally, a phantom power source is used for the condenser microphone. Amicrophone sound signal is output via a balanced shield cable for the phantom power source.
The operation described below is conventionally used as a method for preventing an electromagnetic wave from entering the microphone through the output connector 10. A condenser is connected between the grounding first pin E and the hot-sidesecond pin SH and between the grounding first pin E and the cold-side third pin SC; the condensers operate to short high frequencies. Further, the hot-side second pin SH and the cold-side third pin SC are connected to the microphone case such as theconnector housing cylinder 20 via an inductor that inhibits the entry of high frequencies.
The above conventional technique can inhibit the entry of normal broadcasting electric waves, for example, electromagnetic waves of HF, VHF, or UHF without any problems. However, the recent prevalence of cellular phones and the like hasincreased the opportunities to use an electromagnetic wave of a higher frequency near the microphone.
The three pins E, SH, and SC of the output connector 10 are located directly inside the microphone case. Consequently, a high-frequency current may enter the microphone case through these pins, the high-frequency current resulting from anintense electromagnetic wave radiated by a cellular phone or the like. The high-frequency current then reaches an electronic circuit including an impedance circuit, by radiation or propagation to generate noise.
In particular, noise is made when a high-frequency current coming from the hot-side second pin SH or cold-side third pin SC is electrostatically coupled to the electronic circuit. In other cases, noise is made when high-frequency magnetic fieldsgenerated by a high frequency current flowing through the microphone case are magnetically coupled.
It is thus an object of the present invention to prevent a high-frequency current from entering a microphone case via a pin penetratingly
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