JP2917302B2 - Low frequency circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-frequency circuit having a plurality of low-frequency and high-frequency amplifier circuits.

2. Description of the Related Art In recent years, a CD player has been mounted on a boombox to improve the sound quality, and a multi-amplifier that amplifies each of the low-frequency and high-frequency signals used in high-grade amplifiers in the past has been used. It has become

However, when the above-mentioned multi-amplifier is used for a radio-cassette, a dedicated amplifier for headphones and a headphone / speaker changeover switch must be provided, which requires an expensive circuit configuration, and a radio-cassette having a speaker output terminal. Has a problem that only a dedicated speaker can be used.

The present invention has been made in view of the above problems, and provides a low-frequency circuit that performs headphone / speaker switching without providing a dedicated headphone amplifier, and that can use speakers other than the dedicated speaker.

Means for Solving the Problems To solve the above problems, the low-frequency circuit of the present invention,
A low-pass filter for selectively amplifying the low frequency of the low-frequency input signal, a low-frequency amplifier comprising a low-frequency amplifier; and a high-pass filter for selectively amplifying the high frequency of the low-frequency input signal, and a high-frequency amplifier comprising a low-frequency amplifier. A headphone jack having means for switching the output of one of the amplifier circuits to a headphone output and a speaker output, and a switch interlocking with the plugging / unplugging of the headphone plug; and a headphone jack when the headphone is plugged into the headphone jack by a signal from the switch. And a switching circuit that passes a filter of one of the amplifier circuits.

Operation The present invention enables the use of a speaker other than the dedicated speaker by switching the switch by the above configuration. When using headphones, a signal from a switch interlocked with a headphone plug or a DC voltage superimposed on an output signal is used. With a signal taken out through a headphone plug and a headphone jack ground piece, a signal of an amplifier circuit not connected to the headphone jack is blocked, and a flat headphone output is obtained by passing a filter of one amplifier circuit. Headphone / speaker switching can be performed without providing a dedicated headphone amplifier.

Embodiment Hereinafter, a low-frequency circuit according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a low-frequency circuit according to an embodiment of the present invention. In FIG. 1, a low-frequency input signal A is connected to a speaker through a low-pass filter 1a, a low-frequency amplifier 4a, and an output terminal C. The input signal A is connected to a speaker through a high-pass filter 2a, a low-frequency amplifier 5a, and an output terminal C. On the other hand, switch 3a is a low-pass filter
1a and the input signal A selectively with a low-frequency amplifier 4a.
It is inserted before the low-frequency amplifier 4a for connection to the low-frequency amplifier 4a. The switch 3b is inserted before the low-frequency amplifier 5a to selectively connect the output of the high-pass filter 2a and the input signal to the low-frequency amplifier 5a.

The operation of the low-frequency circuit configured as described above will be described.

When switches 3a and 3b are connected to the filter side,
The low-frequency input signal A is connected to output terminals C and D via the filters 1a and 2a and the low-frequency amplifiers 4a and 5a. The output terminal C is a speaker terminal dedicated to low frequencies, and the output terminal D is a speaker dedicated to high frequencies. Terminal. On the other hand, when the switches 3a and 3b are directly connected to the input signal A which does not pass through the filters 1a and 2a, the low-frequency amplifier 4
Output terminals C and D of a and 5a are output terminals of flat signals.

As described above, according to the present embodiment, a low-pass filter that passes a low band of a low-frequency input signal, a high-pass filter that passes a high band of the input signal, a filter output of each filter, and the input signal that does not pass through a filter. Switch means for switching between low and high frequencies, and a low-frequency amplifier for amplifying each signal in the low and high frequencies.
In addition to obtaining the output of the low-frequency amplifier dedicated to the high band, two flat output systems can be provided, and an arbitrary speaker can be connected in addition to the dedicated speaker composed of the speakers in the low band and the bone region.

Hereinafter, a second embodiment of the present invention will be described with reference to the drawings.

FIG. 2 is a block diagram of a low frequency circuit showing a second embodiment of the present invention, and FIG. 4 is a connection diagram of a headphone jack. In the figure, the case of left and right stereo is illustrated, but the description will be made only for one channel. The low-frequency input signal A is connected to a low-frequency dedicated speaker 8a via a low-pass filter 1a, a muting circuit 6a, and a low-frequency amplifier 4a.
The input signal A is connected to a high-frequency dedicated speaker 9a via a high-pass filter 2a, a switching circuit 7a for switching between a filter output and an input signal not passing through the filter, a low-frequency amplifier 5a, and a headphone jack 11. The output of the low-frequency amplifier 5a is
The headphone jack 11 is connected to a headphone contact 11c of the headphone jack 11 via a headphone volume adjustment resistor 12a. The headphone jack 11 for switching between the speaker and the headphones is the fourth.
Although shown in the figure, the description is omitted because it is already widely used. On the other hand, since the input signal B is also connected in the same manner as described above, the description is omitted. Switch 10 that works in conjunction with the insertion of a headphone plug into headphones 11
Are connected to the muting circuit 6a and the switching circuit 7a.

As described above, according to the present embodiment, a low-pass filter that selectively amplifies a low frequency of a low-frequency input signal, a low-frequency amplifier circuit including a low-frequency amplifier, and a high-pass filter that selectively amplifies a high frequency and a low-frequency amplifier. A headphone jack having a high-frequency amplifier circuit, a means for switching the output of one amplifier circuit between headphones and a speaker, and a switch interlocking with a headphone plug; and a headphone jack when the headphones are plugged into the headphone jack by a signal from the switch. By providing a muting circuit that blocks the signal of the amplifier circuit that is not connected to the amplifier and a switching circuit that passes the filter of one amplifier circuit, when headphones are not used, the amplifier becomes a dedicated amplifier for each of the low band and the high band.
In addition, when using headphones, the muting circuit of the amplifier circuit not connected to the headphone jack is activated by a switch that works in conjunction with the headphone plug to turn off the output.
In addition, a flat headphone output can be obtained by passing the filter of the amplifier circuit connected to the headphone jack.

Hereinafter, a third embodiment of the present invention will be described with reference to the drawings.

FIG. 3 is a block diagram of a low-frequency circuit showing a third embodiment of the present invention. In the figure, the components denoted by the same reference numerals are the same as the components in FIG. 2 is different from the configuration of FIG. 2 in that the output of the low-frequency amplifier 5a is connected to the headphone jack 11 via a coupling capacitor 13a, and the power supply is connected via a resistor 15.
11g is grounded by the capacitor 14, and the voltage between both ends of the capacitor 14 is used as a control signal for the muting circuits 6a and 6b and the switching circuits 7a and 7b.

The operation of the low-frequency circuit configured as described above will be described below.

When the headphones are not used, the output of the low-frequency amplifier 5a is connected to a speaker via the contacts 11a and 11b of the headphone jack 11, and operates as a low-frequency and high-frequency low-frequency amplifier circuit. Here, the resistor 15 connected to the power supply has no influence because it is sufficiently larger than the speaker output. On the other hand, when headphones are used, when the headphone plug is inserted, the output of the low-frequency amplifier 5a is supplied to the headphone via the capacitor 13a, the resistor 12a, the headphone terminal 11c, and the headphone plug. , Grounded through the capacitor 14,
A headphone amplifier circuit is configured. On the other hand, capacitor 13
A power supply connected via a resistor 15 connected after a is superimposed on the low-frequency signal, appears as a voltage across a capacitor 14 connected to a grounding piece 14 of a headphone jack 11 via headphones, and a low-frequency amplifier circuit. Is connected as a control signal to a switching circuit 7a for passing the muting circuit 6a and the high-pass filter 2a.
At the same time, the amplifier circuit connected to the headphone jack 11 is switched to a flat characteristic.

As described above, the output of one amplifier circuit is connected to a power source via a resistor to the headphone jack having means for switching between the headphone and the speaker, and the output side of the one amplifier circuit is connected to the power supply via a resistor. A headphone which is grounded and serves as a control signal for controlling a muting circuit of an amplifier circuit not connected to a headphone jack via a headphone when a headphone plug is inserted, and a filter switching circuit of one of the amplifier circuits.
By providing the speaker switching means, the same effect as in the second embodiment can be obtained.

Although the description has been given of only one low-frequency input signal A, the description is omitted for the input signal B since it is the same.

Further, in the second and third embodiments, the high-frequency amplifier circuit is connected to the headphone jack, but the low-frequency amplifier circuit may be connected to the headphone jack.

As described above, the present invention comprises a low-pass filter that selectively amplifies a low frequency of a low-frequency input signal and a low-frequency amplifier circuit including a low-frequency amplifier, and a high-pass filter that selectively amplifies a high frequency and a low-frequency amplifier. When a headphone plug is inserted into the high-frequency amplifier circuit and the headphone jack, a signal from a switch that works in conjunction with the plug insertion or a DC voltage superimposed on the output signal is passed through the headphone plug and the earthing piece of the headphone jack. A headphone is used by providing a muting circuit that blocks a signal of an amplifier circuit that is not connected to the headphone jack and a switching circuit that passes a filter of one of the amplifier circuits by a signal from a circuit configured to supply the signal. If not, there is no dedicated amplification circuit for each of the low and high frequencies. At the same time as the plug is inserted, the output of the amplifier circuit not connected to the headphone jack is turned off, and the output of the amplifier circuit connected to the headphone jack can be made a flat headphone output. Headphones / speakers can be switched.

[Brief description of the drawings]

FIG. 1 is a block diagram of a low-frequency circuit according to a first embodiment of the present invention, FIG. 2 is a block diagram of a low-frequency circuit according to a second embodiment of the present invention, and FIG. FIG. 4 is a block diagram of a low-frequency circuit according to the embodiment.
It is a connection diagram of the headphone jack of the figure. 1a, 1b low-pass filter, 2a, 2b high-pass filter, 3a, 3b changeover switch, 4a, 4b, 5a, 5b low-frequency amplifier, 6a, 6b muting circuit, 7a, 7b ... Switching circuit, 10 ... Link switch, 11 ... Headphone jack,
14: Capacitor, 15: Resistor.

Claims (2)

(57) [Claims] A low-pass filter for selectively amplifying a low frequency of a low-frequency input signal, a low-frequency amplifier comprising a low-frequency amplifier;
A high-pass filter for selectively amplifying the high frequency of the low-frequency input signal; a high-frequency amplifier comprising a low-frequency amplifier; a means for switching the output of one of the amplifier circuits to a headphone output and a speaker output; A muting circuit for blocking a signal of an amplifier circuit not connected to the headphone jack when the headphone is inserted into the headphone jack by a signal of the switch, and a switching circuit for passing a filter of one of the amplifier circuits And a low-frequency circuit comprising: 2. A low-pass filter for passing a low frequency of the low-frequency input signal, a high-pass filter for passing a high frequency of the low-frequency input signal, and the respective filter outputs and the low-frequency input signal not passing through the filter. Switch means for switching between the low frequency range selected by the switch means,
A low-frequency amplifier for amplifying each of the high-frequency signals; and a means for switching the output of one of the amplifier circuits to a headphone output and a speaker output. And a grounding side of the headphone jack is grounded by a capacitor, and when a headphone plug is inserted, a muting circuit of the other amplifier circuit is connected via a headphone.
A low-frequency circuit comprising headphone / speaker switching means for generating a control signal for controlling a filter switching circuit of one of the amplifier circuits.