JPH0127353Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control circuit for an audio device having left and right channels, that is, a stereo audio device. Recently, audio equipment called a tape recorder with radio, which is a combination of a radio receiver and a tape recorder, has become popular, but most of these audio equipment are of a stereo type having left and right channels. With portable audio equipment, it is difficult to obtain a good stereo effect due to the narrow spacing between the left and right speakers, so this type of audio equipment is equipped with a sound field expansion circuit that electrically expands the left and right sound fields. ing. A common method for such a sound field expansion circuit is to change the phases of the left and right channel signals and add them to the other channel. Although such a system can be easily constructed, it has the disadvantage that the central sound is omitted, which gives the listener an extremely unnatural feeling, especially when listening to music through a headphone. The present invention has been developed in view of the above-mentioned points, and will be described in detail below with reference to the illustrated embodiments. In the illustrated circuit, 1 and 2 are input terminals into which left and right signals such as tape recorder playback signals are input, and 3 and 4 are input terminals 1 and 2.
5 and 6 are left and right speakers connected as loads for the first and second amplification circuits 4, and 7 is a stereo headphone. This is a headphone jack into which a plug is inserted, and is configured to cut off the signal supply path to the speakers 5 and 6 when the headphone plug is inserted.
8 and 9 are negative feedback circuits 10 and 11 for determining the gains of the first amplifier circuit 3 and the second amplifier circuit 4.
first and second feedback resistors connected within the first and second feedback resistors.
Reference numerals 12 and 13 indicate first and second control switches that are opened when the headphone plug is inserted into the headphone jack 7, and 14 and 15 indicate that the first control switch 12 and the second control switch 13 are in the closed state. third and fourth feedback resistors that are connected in parallel to the second feedback resistor 9 and the first feedback resistor 8 when 16 is a first sound field enlarging circuit connected between the output terminal of the first amplifying circuit 3 and the negative feedback circuit 11 of the second amplifying circuit 4, and is closed when the resistor 17 and sound field enlarging operation is performed. It is composed of a first selection switch 18. 19 is a second sound field expansion circuit connected between the output terminal of the second amplifier circuit 4 and the negative feedback circuit 10 of the first amplifier circuit 3;
and a second selection switch 21 that is closed during the sound field expansion operation. The present invention is constructed as described above, and its operation will be explained next. In the illustrated state, the first selection switch 18 and the second selection switch 21 are open, and the first sound field expansion circuit 16 and the second sound field expansion circuit 19 are in an inactive state. In such a state, the tape recorder playback signals inputted to the input terminals 1 and 2 are amplified by the first amplifier circuit 3 and the second amplifier circuit 4, and then applied to the speakers 5 and 6 to emit sound. be done. Since the sound field expansion circuits 16 and 19 do not operate in such a state, it is not possible to obtain a good stereo sound from the speakers 5 and 6, but it is possible to insert the headphone plug into the headphone jack 7 and turn the headphone on. Therefore, by listening to the reproduced signals, etc., which are the output signals of the amplifier circuits 3 and 4, a good stereo feeling can be obtained.
Also, when listening with such a headphone, the first control switch 12 and the second control switch 1
3 is open, the third feedback resistor 14 and the fourth feedback resistor 15 are in a state separated from the negative feedback circuits 11 and 10 . Therefore, speaker 5,
Since the gains of the first amplifier circuit 3 and the second amplifier circuit 4 will be lower than when listening to the signal emitted by the headphone, it is necessary to apply a signal of an appropriate level to the headphone. and will be heard. When the first selection switch 18 and the second selection switch 21 are closed while listening to reproduced signals etc. through the speakers 5 and 6, the second sound field expansion circuit 16 and the second sound field expansion circuit 19 are activated. become a state. When the first sound field enlarging circuit 16 and the second sound field enlarging circuit 19 are activated, phase control of the signals of the left and right channels is performed, and the signals of the speakers 5 and 6 are controlled.
As a result of the emitted sound signal being expanded further, the user can obtain a good stereo feeling. Next, the first selection switch 18 and the second selection switch 21 are closed, that is, the first sound field expansion circuit 1
The operation of inserting the headphone plug into the headphone jack 7 when the headphone plug 6 and the second sound field enlarging circuit 19 are in operation will be described. When the headphone plug is inserted into the headphone jack 7, the first control switch 12 and the second control switch 13 are opened. As a result, the first sound field expansion circuit 16 and the second sound field expansion circuit 19 are connected to the negative feedback circuit 1.
1 and 10 and the third feedback resistor 1
4 and the fourth feedback resistor 15 are the negative feedback circuits 11 and 1
Separated from 0. As a result of such separation, the sound field expansion effect disappears and the gains of the first amplifier circuit 3 and the second amplifier circuit 4 decrease. Therefore, the level of the signal applied to the headphone is at an appropriate level, and the center sound does not drop out, making it possible to listen to good reproduced sound. In this embodiment, the first control switch 12, the second control switch 13, the first selection switch 18, and the second
Although a mechanical switch is used as the selection switch 21, a switching element such as a transistor may also be used. As explained above, the control circuit of the present invention can be applied to a headphone jack in an audio device configured to have a narrow gap between left and right speakers and to obtain a stereo effect through the operation of a sound field expansion circuit. When the plug is inserted, the control switch that is switched by the insertion of the plug disables the sound field expansion operation of the sound field expansion circuit, which solves the problem of missing the center sound when listening with a headphone. . In addition, the present invention has a control switch that controls the operation of the sound field expansion circuit and is opened when the headphone plug is inserted into the headphone jack. Since it is connected to a feedback circuit and the gain of the amplifier circuit is lowered by opening the feedback circuit, it is possible to listen to the signal using the headphone at an appropriate level without having to adjust the volume. By switching the gain of the amplifier circuit, the signal level during listening operation by the headphone is lowered, compared to a configuration in which the signal level is lowered by inserting and connecting a resistor in the signal path to the headphone. The present invention has the advantage that listening operations can be carried out efficiently. Furthermore, when listening with a head-on, the amount of negative feedback in the amplifier circuit increases, which improves the distortion characteristics of the amplifier circuit, which is extremely effective when listening with a head-on, where distortion is likely to be audible. Therefore, the practical value of the present invention is very high.

[Brief explanation of the drawing]

The illustrated circuit is one embodiment of the control circuit of the present invention. Explanation of main drawing numbers, 3...first amplifier circuit, 4...
Second amplifier circuit, 7...headphone jack, 1
0, 11 ...Negative feedback circuit, 12...First control switch, 13...Second control switch, 16 ...First
Sound field expansion circuit, 19 ...Second sound field expansion circuit, 18
...First selection switch, 21...Second selection switch.

Claims (1)

[Scope of utility model registration request] a first amplifier circuit and a second amplifier circuit that amplify the left and right channel signals, respectively; a first speaker and a second speaker to which the left and right channel signals amplified by the first amplifier circuit and the second amplifier circuit are respectively applied;
When the output signals of the speaker, the first amplifier circuit, and the second amplifier circuit are applied, and the head-on plug is inserted, the first speaker and the second amplifier circuit are connected.
a headphone jack that blocks a signal path to the speaker; a first sound field expansion circuit provided between the output terminal of the first amplifier circuit and a negative feedback circuit that controls the gain of the second amplifier circuit; , a second sound field expansion circuit provided between the output terminal of the second amplifier circuit and a negative feedback circuit that controls the gain of the first amplifier circuit; a negative feedback circuit of the second amplifier circuit and a first amplifier circuit; a first control switch connected between the sound field enlarging circuit and disconnecting the first sound field enlarging circuit from the negative feedback circuit and reducing the gain of the second amplifying circuit when in an open state; connected between the negative feedback circuit of the first amplifying circuit and the second sound field enlarging circuit, and disconnecting the second sound field enlarging circuit from the negative feedback circuit when the first amplifying circuit is in an open state; a second control switch for reducing the gain of the circuit, opening the first control switch and the second control switch when the headphone plug is inserted into the headphone jack;
Control of a stereo audio device, characterized in that the sound field expansion operation by a sound field expansion circuit and a second sound field expansion circuit is disabled, and the gains of the first and second amplifier circuits are reduced. circuit.