JPH0115023Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a muting circuit in a so-called soft operation tape recorder that uses the rotational force of a motor to move a slide base or a lever to perform recording or playback.

Recently, due to the rotational force of the motor, the slide base,
Alternatively, soft operation tape recorders have appeared in which various operating states such as recording and playback can be obtained by moving a metal fitting provided with an idler. In such a soft operation tape recorder, noise is generated due to large fluctuations in the power supply voltage that occur when the motor is started, and due to the rising voltage of the amplifier. Such popping noises occur until the slide base, on which the magnetic head and the like are installed, reaches the operating position relatively slowly due to the rotational force of the motor.

Therefore, the present invention provides a muting switch in series with the speaker or headphone, and when the slide base is being moved by the rotational force of the motor, the muting switch is turned off to disable the speaker or headphone, thereby preventing pop noise from occurring. The present invention provides a muting circuit that eliminates the

The present invention will be described below with reference to the drawings. Reference numeral 1 denotes a magnetic head for reproducing signals recorded on a tape 2. The magnetic head 1 is mounted on a slide base (not shown) that is slid by the rotational force of a motor 3. It is set in. 4 and 5 are amplifier circuits that amplify the signals reproduced by the magnetic head 1; 6 is a speaker connected to the output side of the amplifier circuit 5 via a DC blocking capacitor; and the slide base is connected in series to the speaker 6. A muting switch 7 is connected thereto, which is turned on when the switch is placed in the playback state. Furthermore, a resistor 8 having a resistance value sufficiently larger than the resistance value of the speaker 6 is connected in parallel to the muting switch between the speaker 6 and the ground. 9 is a power switch, and 10 is a power source.

Next, the operation of the muting circuit of the present invention will be explained. If the playback button is now pressed to perform playback, the power switch 9 is turned on. Thereby motor 3
A voltage from a power source 10 is supplied to the motor 3.
is rotated. First, slide the slide base or other levers required to bring the device into the playback state. At this time, since the voltage from the power supply 10 is applied to the amplifier circuits 4 and 5, the sudden voltage change that occurs when the motor 3 is started becomes pop noise and is applied to the speaker 6, which may generate noise. However, since the muting switch 7 is now turned off, no noise is generated from the speaker 6, and the pop noise is grounded through the resistor 8, and is connected to the DC blocking capacitor connected to the output side of the amplifier circuit 5. DC current flows through and charges the battery. After a period of time (approximately 1 second), the slide base is placed in the regeneration state, and the idler etc. are also placed in the regeneration state. Therefore, the rotational force of the motor 3 is transmitted to the reel shaft via the capstan, idler, etc., and runs the tape 2. Since the muting switch 7 is turned on by placing the slide base in the reproduction state, the signal reproduced by the magnetic head 2 is amplified by the amplifier circuits 4 and 5 and then drives the speaker 6. Also, before the mutating switch 7 is turned on, a DC current gradually flows through the resistor 8 to charge the DC blocking capacitor, so when the mutating switch 7 is turned on, a DC current suddenly flows to the DC blocking capacitor. , it is not supplied to the speaker 6 and generates noise, and the resistor 8 remains connected even after the muting switch 7 is turned on, but it is sufficiently large compared to the resistance value of the speaker 6. Therefore, there is no effect.

It is of course possible to use a headphone instead of the speaker 6.

As mentioned above, the mutating circuit of the present invention has the following features:
A muting switch that is turned on when the slide base is in the operating position is connected between an acoustic transducer such as a speaker and ground, and a resistor having a larger impedance than the acoustic transducer is connected in parallel to the muting switch. so that the acoustic transducer is activated after the slide base is positioned in the playback condition;
Therefore, in devices such as motor-operated tape recorders in which the slide base is slid by the rotation of the motor, the load placed on the motor is large, so even if the power supply voltage fluctuates greatly when the motor is started, and pop noises occur, the acoustic transducer cannot be used. Also, before the mutating switch is turned on, a DC current flows through the resistor and is charged in the DC blocking capacitor connected to the output side of the amplifier, so when the mutating switch is turned on, no DC current is applied. This prevents a large charging current from suddenly flowing into the blocking capacitor and causing noise.

[Brief explanation of the drawing]

The figure is a mutating circuit diagram of the present invention. 6... Speaker, 7... Muting switch, 8... Resistance.

Claims (1)

[Scope of utility model registration request] In a device that slides a slide base using the rotational force of a motor, a muting switch that is turned on when the slide base is in the operating position is connected between the acoustic transducer and ground, and the acoustic transducer is connected in parallel to the mutating switch. A muting circuit characterized in that a resistor having an impedance greater than that of a converter is connected.