In one embodiment, a directional microphone array having two microphones generates forward and backward cardioid signals from two microphone signals. The invention proposes to divide the plug connector housing in the insertion direction into a front and a rear housing section that are connected to a hinge joint by means of a swivel axle that is oriented orthogonally to the insertion direction. Diameter-reduced portions 11a and 11b are formed in the vicinity of the ends of the glass pipe 11. The grip reduces impact shock and provides a feeling of tackiness in the manner of a spirally wrapped polyurethane-felt grip while allowing the use of multiple color panels and inserts, easy installation onto a golf club shaft, and placement of various materials in various grip areas. Accordingly, the flicker or image-sticking can be prevented. This process enables a reduction in a residual noise during gain control included in a signal output from the amplifier 15 at the final stage.