JPH0316500A - Voice output volume interlocking with headphone output - Google Patents

Abstract

PURPOSE:To improve the assembling by providing a voltage control amplifier having a control input whose gain is variable depending on a DC applied voltage and a means applying the variable voltage to the control input of the amplifier and connecting the output of the amplifier to both a headphone drive output circuit and a voice output circuit. CONSTITUTION:The output of a voltage control amplifier 11 is inputted to a headphone amplifier 3 and its output is connected to both headphone output terminal 5 of a front face board via a wire and a voice output terminal 6. Moreover, a control terminal of a voice control amplifier 11 is connected in common with the control terminal of the voltage control amplifier 12 of other channel and is connected to a slider of a headphone variable resistor on the front board 10 via a wire. A fixed terminal of the headphone variable resistor is connected to a DC power supply 14. Thus, both the sound output and the headphone output are changed by adjusting the headphone variable resistor 13 of the front face board 10 simultaneously and outputs of both stereo channels are changed simultaneously.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to means for varying the audio output level of a VTR or the like.

[Prior Art] FIG. 2 shows an example of a headphone output-linked audio output volume according to the prior art. Since this diagram is a stereo circuit, only one channel will be explained. In equipment such as a VTR, circuit components are generally arranged on a board, and an operation section is generally arranged on the front side of the equipment by means of a front board. Therefore, this example is composed of an audio board 9 on which an audio circuit is arranged, an output volume 8, a front board 10 on which a headphone terminal is arranged, and a wire connecting them. First, the audio signal is input from 1, connected to one input of volume 8 on the front board via a wire, and after adjusting the level with the volume, returns to the audio board via the wire again and input to headphone amplifier 3. be done. The output of the headphone amplifier 3 is connected to the audio output terminal 6, and at the same time is connected to the headphone terminal on the front board via a resistor and a wire. The same goes for the other channel.

According to this structure, by changing the volume 8 on the front board, both the audio output and the headphone output can be changed at the same time.

[Problems to be Solved by the Invention] The above conventional technology requires six wires between the audio board and the front board, and all of them are audio signals, so noise from other control signal lines etc. If the wire jumps into the wire, the SN of the audio signal deteriorates, so there is a possibility that the wire will become a shield, making assembly difficult and expensive.

It is an object of the present invention to eliminate the problems of the prior art described above and to improve assembly workability and cost performance.

[Means for solving the problem] In order to achieve the above object, a voltage control amplifier whose gain changes depending on the DC voltage applied to the control terminal is used, and by changing the DC voltage, [Operation] The output volume adjusts the DC voltage. The gain of the voltage-controlled amplifier is changed depending on the voltage, and the output level of the headphone terminal and sound/voice output terminal connected to the output circuit is changed.

[Example] Hereinafter, an example of the present invention will be described with reference to FIG. Since this diagram is a stereo circuit, only one channel will be explained. An audio signal is input from 1 and is input to a voltage control amplifier 11 whose gain changes depending on the DC voltage applied to the control terminal.

The output of the voltage control amplifier 11 is input to the headphone amplifier 3, and its output is connected to both the audio output terminal 6 and the headphone output terminal 5 on the front board via a wire.

Further, the control terminal of the voltage control amplifier 11 is commonly connected to the control terminal of the voltage control amplifier 12 of the other channel, and is further connected to the variable side of the headphone volume of the front substrate 10 via a wire. There are headphones. Therefore, the headphone volume 13 of the front board 10
By changing the output level of the audio output and the headphone output, it is possible to change the output level of both stereo channels at the same time. Voltage control amplifier. I
It is often converted into C and is available at low cost.

Further, according to this example, only three wires are required between the audio board 9 and the front board 10, and since the audio signal is transmitted through only two wires for headphones with low impedance, there is less need for shielding wires. It is easy to assemble, and even in a stereo circuit, a single volume can be used because the DC voltage can be varied simultaneously for both channels, which has the effect of reducing costs.

[Effects of the Invention] According to the present invention, by using a voltage control amplifier that can be controlled by DC voltage and a volume that varies the DC voltage, the connection between the audio board and the front board is simplified. This has the remarkable effect of significantly contributing to improved workability and cost reduction.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a headphone output-linked audio output volume according to an example of the present invention, and FIG. 2 is a circuit diagram of a headphone output-linked audio output volume according to the prior art. 1...L audio input 2...R audio input 3...L amplifier 4...R amplifier 5...Headphone jack 6...L audio output 7...R audio output 8... Headphone volume (2 sets) 9... Audio board 10... Front board 11... L voltage control variable gain amplifier 12... R voltage control variable gain amplifier 13... Hesodophone volume (single set) 14 ...DC power supply Figure 1 1...L audio power 2...R audio power 3...L amplifier 4...R amplifier ft9 /Ori 5...Headphone jack 6...L Audio output 7...R audio output Figure 2

Claims (2)

[Claims] 1. In an audio output circuit equipped with a headphone output terminal, an audio output terminal, a headphone amplifier, and a headphone volume, there is a voltage control amplifier equipped with a control input whose gain can be varied depending on the DC applied voltage value, and a variable control input of the amplifier. 1. A headphone output-linked audio output volume, comprising means for applying a voltage, and an output of the amplifier is connected to both a headphone driving output circuit and an audio output circuit. 2. In the first term, each of the headphone driving output circuit and the audio output circuit is independently provided with the voltage control amplifier of the first term,
A headphone output-linked audio output volume, characterized in that the control output terminals of the voltage control amplifier are commonly connected to means for applying a variable voltage.