JPH0314817Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to an audio device equipped with a muting device.

[Conventional technology]

FIG. 2 is a block diagram of the main parts of an audio device having a conventional muting device. In the figure, 1 is an audio signal source that outputs a two-channel audio signal, for example, a radio detection output, and 2 is a signal source from this signal source. 3 is a sound quality controller to which the audio signal balanced by this balance controller is input; 4 is a volume adjustment switch; 5 is an output pulse width controlled by the operation of this volume adjustment switch 4; A variable electronic volume controller; 6 is a smoothing circuit that converts the output pulses of this electronic volume controller into a DC voltage and outputs a volume control signal; 7 is a smoothing circuit that converts the output pulses of this electronic volume controller into a DC voltage and outputs a volume control signal; 7, which converts the audio signal from the sound quality controller and the volume control signal from this smoothing circuit An electronic attenuator 9 receives the audio output of the electronic attenuator via a capacitor 8 and sends the audio signal to four output terminals 9a to 9d. This is a fader controller for outputting, and is composed of four resistors 91 to 94 and two variable resistors 95 and 96. 11 are the four output terminals 9a to 9 mentioned above.
d are connected to power amplifiers via capacitors 10, 12 is a muting signal source which is composed of, for example, a microcomputer and outputs a mute signal, and 13 is composed of a resistor and a capacitor that receive mute signals from this mute signal source. A time constant circuit 14 receives the muting signal from the muting signal source 12 via the time constant circuit, and receives the muting signal from the muting signal source 12 through the output terminals 9a to 14 of the fader controller 9.
This is a muting circuit that mutates the audio signal from 9d, and the output terminals 9a to 9
d and ground, each resistor 141
It is constituted by four transistors 14a to 14d whose bases receive the mute signal via transistors 144 to 144, and these transistors 14a to 14d become conductive when the mute signal is input. Note that the muting signal source 12, the time constant circuit 13, and the muting circuit 14 constitute a muting device.

Next, in the device configured in this way, the muting operation in particular will be explained. The audio signal from the audio signal source 1 is outputted via a balance controller 2, a sound quality controller 3, an electronic attenuator 7, a fader controller 9, and a power amplifier 11. When a muting signal is now output from the mutating signal source 12, this muting signal is transmitted to the time constant circuit 13.
The signal is inputted to the bases of transistors 14a to 14d of the muting circuit 14 via. Since these transistors 14a to 14d are rendered conductive by the mute signal, the fader controller 9
The output terminals 9a to 9d of these transistors 14a
14d, and the audio signal is no longer transmitted to the power amplifier 11.

[Problem that the invention attempts to solve]

However, an audio device equipped with a muting device configured in this manner has the following problems. First, in order to attenuate the audio signal from the fader controller 9 to a large extent, it is necessary to reduce the on-resistance of the transistors 14a to 14d, which places restrictions on the transistors 14a to 14d. Second, in general, it is better to have a fast attack time and a slow recovery time, but in the time constant circuit 13, if the attack time is made faster, that is, the charging time constant is made smaller, the recovery time is also made faster, that is, the discharge time constant is also made smaller. Put it away. Third, transistor 1
Since 4a to 14d are directly connected to the audio signal transmission path, care must be taken to prevent distortion and noise from being mixed in.

This idea was made in view of the above points, and has a very simple circuit configuration with few design restrictions, large attenuation of audio signals, fast attack time, slow recovery time, and distortion. The object of the present invention is to obtain a muting device with less noise and interference.

[Means for solving problems]

The audio device according to this invention has a smoothing circuit that converts the output pulse of an electronic volume controller whose output pulse width is variable according to the operation of a volume adjustment switch into a DC voltage and outputs a volume control signal. A resistor is connected between the input terminal from the controller and the control terminal of the electronic attenuator which is the output terminal thereof, and a capacitor is connected between this control terminal and the ground potential. A switching means is provided, which has a transistor connected to a ground potential and becomes conductive when a muting signal from a muting device is input to its base, and maximizes the amount of attenuation of the electronic attenuator by making the transistor conductive. It is something that

[Effect]

In this device, when the switching means receives a mute signal, its transistor becomes conductive, and the potential at the control end of the electronic attenuator rapidly decreases due to the discharge time constant of the smoothing circuit's capacitor and the transistor's on-resistance. It becomes the ground voltage, and the attenuation amount of the electronic attenuator becomes maximum with a short attack time. On the other hand, when the mute signal disappears, the transistor becomes non-conductive, and the potential at the control terminal of the electronic attenuator rises to the potential of the volume control signal due to the charging time constant of the capacitor and resistor of the smoothing circuit, returning to the original state with a fairly slow recovery time. to return to.

〔Example〕

An embodiment of this invention will be described below with reference to FIG. 14 is a switching means that receives a muting signal from the muting signal source 12 and maximizes the amount of attenuation of the electronic attenuator 7; It is constituted by a transistor 14a to which a signal is inputted to its base, and becomes conductive when a mute signal is inputted, thereby bringing the control end 7a of the electronic attenuator 7 to the ground potential.

Next, the operation of the device configured in this way will be explained. An audio signal from an audio signal source 1 is outputted via a balance controller 2, a sound quality controller 3, an electronic attenuator 7, a fader controller 9, and a power amplifier 11. To adjust the volume of the audio signal, by operating the volume control switch 4, an output pulse having a pulse width corresponding to the operation is output from the electronic volume controller 5, and a DC potential corresponding to the pulse width of this output pulse is output. A volume control signal consisting of
This is done by adjusting the amount of attenuation of the electronic attenuator 7 by applying it to a. This electronic attenuator 7 has a smaller attenuation amount as the DC potential applied to the control end 7a becomes higher.
The amount of attenuation is maximum when it reaches 0V, that is, the ground potential. Now, when a mute signal is output from the muting signal source 12, this mute signal is input to the base of the transistor 14a. Since this transistor 14a is rendered conductive by the mute signal, the control end 7a of the electronic attenuator 7 is grounded via the transistor 14a. At this time, the capacitor 6a of the smoothing circuit 6
Since the charged charge is also discharged via the transistor 14a, the control terminal 7a becomes the ground potential. As a result, the amount of attenuation of the electronic attenuator 7 becomes almost the maximum (more than 70 dB), and the transmission of audio signals from the electronic attenuator 7 is almost eliminated. The attack time at this time is determined by the discharge time constant of the capacitor 6a of the smoothing circuit 6 and the on-resistance of the transistor 14a, and the on-resistance of the transistor 14a is almost negligible compared to the resistance 6b of the smoothing circuit 6 (for example, about 10KΩ), so it can be done quickly. It is something. On the other hand, when the muting signal from the muting signal source 12 disappears, the transistor 14a becomes non-conductive, so the capacitor 6b of the smoothing circuit 6 is charged by the output pulse from the electronic volume controller 5, and the control terminal 7b
A DC potential is applied to the electronic attenuator 7, and the electronic attenuator 7 returns to its original state. Therefore, the audio signal will be transmitted. Since the recovery time at this time is determined by the charging time constant of the capacitor 6a and the resistor 6b of the smoothing circuit 6, it can be made quite slow.

In the mutating device configured in this way, the muting circuit 14 can be configured with one transistor 14a, so the circuit configuration is simple, and this transistor 14a is connected to the control terminal 7.
Since it is only necessary to lower the potential of a to the ground potential, it is not necessary to pay much attention to variations in h _FE and on-resistance of the transistor, and design latitude is increased. Furthermore, as mentioned above, the attack time is fast and the recovery time is slow, making it possible to approximate the ideal mutating device, and by making the capacitor 6a of the smoothing circuit 6 variable.
Optimal attack and recovery times can be set for multiple models, making it easy to standardize. Furthermore, the audio signal is muted by setting the control end 6a of the electronic attenuator 6 to ground potential, and the muting circuit 14 is not connected to the audio signal transmission path, so distortion and noise are prevented from being mixed in. It almost disappears.

[Effect of idea]

As mentioned above, this invention uses a smoothing circuit that converts the output pulses of an electronic volume controller, whose output pulse width is variable according to the operation of the volume adjustment switch, into DC voltage and outputs a volume control signal. A resistor is connected between the input end of the electronic volume controller and the control end of the electronic attenuator, which is the output end of the electronic volume controller, and a capacitor is connected between the control end and the ground potential, and the electronic attenuator is controlled. It has a transistor that is connected between the end and the ground potential and becomes conductive when a mute signal from the muting device is input to the base, and when the transistor is conductive, the attenuation of the electronic attenuator is changed and the mute signal is received. Since a switch means is provided to maximize the output power, the circuit configuration is simple, there are few design restrictions, the amount of attenuation of the audio signal can be large, the attack time is fast, the recovery time is slow, and the distortion is reduced. This has the effect of providing an acoustic device equipped with a muting device that generates less noise and mixes less noise.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 is a block diagram of essential parts showing an audio device having a conventional muting device. In the figure, 4 is a volume adjustment switch, 5 is an electronic volume controller, 6 is a smoothing circuit, 6a is a capacitor, 6b is a resistor, 7 is an electronic attenuator,
7a is a control end, 12 is a mutating signal source, 1
4 is a muting circuit, and 14a is a transistor. In each figure, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Scope of utility model registration request] An electronic volume controller that changes the output pulse width according to the operation of a volume adjustment switch, a smoothing circuit that converts the output pulses of this electronic volume controller into DC voltage and outputs a volume control signal, and a volume control signal from this smoothing circuit. Based on the above, in an audio device equipped with an electronic attenuator that changes the amount of attenuation of an input audio signal, and a muting device that outputs a muting signal for the audio signal, the smoothing circuit is connected to the input from the electronic volume controller. A resistor is connected between the terminal and the control terminal of the electronic attenuator, which is the output terminal thereof, and a capacitor is connected between the control terminal and the ground potential. connected between
An acoustic device characterized in that the base includes a transistor that becomes conductive when a mute signal from the mutating device is input, and switching means is provided for maximizing the amount of attenuation of the electronic attenuator by making the transistor conductive. .