JPS5921597Y2 - Microphone talk switch device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a microphone talk switch device, and is particularly designed to prevent the generation of noise during switching.

Some microphones are equipped with a talk switch for supplying or cutting off the output to a next-stage amplifier or the like.

In a tape recorder or the like, for example, when the speaker's voice is interrupted, the talk switch is closed to prevent unnecessary surrounding sounds from being added to the recording amplifier at the next stage.

In conventional condenser microphones that have a built-in power supply battery and are equipped with an output transformer, a talk switch is installed on the secondary side of the transformer, and to cut off the output signal, close this switch to short-circuit the secondary coil. I was trying to do that.

For this reason, when the switch is opened or closed to turn on or cut off the direct current from the power supply battery, click noise occurs due to charging and discharging of the coupling capacitor between the microphone and the subsequent circuit.

Such noise is emitted from a speaker through an amplifier, or is recorded on a magnetic tape in the case of a tape recorder.

The present invention is intended to eliminate the above-mentioned drawbacks, and it connects a series circuit of a capacitive element and a switch in parallel with the load of an impedance conversion element such as a FET, and also connects a resistive element with a high resistance value in parallel with the switch. is connected.

An example in which the present invention is applied to a condenser microphone will be described below.

FIG. 1 shows a first embodiment.

In FIG. 1, a capacitor 1 is formed by a vibrating electrode plate and a fixed electrode plate of a microphone, and its capacitance changes depending on the frequency and level of audio.

One end of this capacitor 1 is connected to the gate electrode G of an N-channel FET (field effect transistor) 2 for impedance conversion, and the source electrode of this FET 2 is connected to the negative side of a battery 3 built into the microphone. .

The positive side of the battery 3 is connected to the drain electrode of the FET 2 and the other end of the capacitor 1 via the primary coil of the output transformer 4.

Further, a series circuit of a resistor 7 and a capacitor 8 is connected in parallel to the primary coil, and a talk switch 9 is further connected in parallel to the resistor 7.

As shown in the figure, the polarity of the capacitor 8 matches the DC potential of the battery 3.

An output terminal 5.6 is connected to the secondary side of the output transformer 4.

The resistance value R of the resistor 7 is a high resistance of, for example, 50Ω or more, and the capacitance C of the capacitor 8 is, for example, 10 μF or more, which is sufficiently smaller than the impedance of the lance 4.

In the above configuration, when the talk switch 9 is turned off, since the resistor 7 having a high resistance value R is connected, the impedance seen from the transformer 4 side becomes sufficiently high, and the load on the FET 2 is only the transformer 4. Become.

As a result, a change in capacitance of the capacitor 1 according to the audio frequency and level is converted into a change in the drain current of the FET 2, and an audio signal is output from the secondary output terminals 5 and 6 of the transformer 4 due to this current change.

Next, when the switch 9 is turned on in this state, the impedance determined by the capacitance C of the capacitor 8 becomes much smaller than the impedance of the transformer 4, so the audio signal flows through the capacitor 8, and therefore, there is no output at the output terminals 5 and 6. It does not appear.

While the talk switch 9 is OFF, the potential of the positive electrode side of the capacitor 8 is approximately equal to the potential of the battery 3 via the resistor 7, so even if the talk switch 9 is turned ON next time, the potential of the positive electrode side will not change. There is no click noise.

Furthermore, even when switching from ON to OFF, no click noise occurs because the capacitor 8 is connected to the battery 3 via the resistor 7.

Furthermore, since the polarity of the capacitor 8 is matched to the DC potential of the circuit, no induced charge is formed on the capacitor 8, and depending on the connection between the capacitor 8 and the talk switch 9, the talk switch 9 can be turned on or off. This is to prevent noise from occurring.

2 to 4 show embodiments 2 to 4, which are modified examples of the circuit in FIG. 1, and all of them operate in the same way as in the case of FIG. 1.

FIG. 5 shows a fifth embodiment, in which a resistor 10 is used in place of the transformer 4 as the load of the FET 2, and an output is obtained through a coupling capacitor 11 at output terminals 5 and 6.

In each of the first to fifth embodiments described above, the resistor 7 may be omitted and R=.

In that case, when the talk switch 9 is closed for the first time, the capacitor 8 is charged, so a click noise is generated, but thereafter, even if the talk switch 9 is turned ON-OFF, no click noise is generated.

Also, although I have talked about condenser microphones above,
The present invention is generally effective when applied to a microphone that incorporates an impedance conversion element such as an FET and a power supply battery for operating the element.

As mentioned above, the present invention uses an impedance conversion element (
For example, in a microphone that includes a built-in FET 2) and a power supply battery for operating this impedance conversion element, a capacitive element (for example, capacitor 8) and a switch (for example, At the same time as connecting a series circuit with the switch 9), a resistor element having a high resistance value (for example, the resistor 7) is connected in parallel with the switch, and when the switch is in the first position (for example, the ON position), the The microphone is configured to pass the output signal of the impedance conversion element to the capacitive element, thereby blocking the output signal to the output terminal, and applying the output signal to the output terminal at the second position (for example, OFF position) of the switch. This is related to the talk switch.

Therefore, according to the present invention, it is possible to prevent click noise from occurring when the talk switch is turned on and off with a simple circuit configuration.

[Brief explanation of drawings]

1 to 5 are circuit diagrams of condenser microphones showing first to fifth embodiments of the present invention, respectively. In addition, in the symbols used in the drawings, 2 is FET,
3 is a power supply battery, 4 is an output transformer, 5 and 6 are output terminals,
8 is a capacitor, 9 is a talk switch, and 10 is a resistor.

Claims (1)

[Scope of utility model registration request] In a microphone incorporating an impedance conversion element and a power battery for operating the impedance conversion element, a series circuit of a capacitive element and a switch is connected in parallel with the load of the impedance conversion element, and the switch A resistance element having a high resistance value is connected in parallel, and the output signal of the impedance conversion element is passed through the capacitance element in the first position of the switch to cut off the output signal to the output terminal. A talk switch for a microphone, wherein a second position of the switch applies the output signal to the output terminal.