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JPH0644293

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
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DESCRIPTION JPH0644293
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
signal passband switching circuit capable of deep bass reproduction.
[0002]
2. Description of the Related Art A subwoofer is used to reproduce low tones to lower
frequencies and with a large scale. The signal input to the subwoofer is about 150 Hz or less. In
this frequency band, the direction interval of the human ear becomes dull and it becomes difficult
to distinguish the directionality of the sound, so in addition to the advantage that the installation
location of the subwoofer is not restricted, its effect is also effective in sound field reproduction It
is done.
[0003]
FIG. 1 shows an example of the configuration of a signal pass band switching circuit for
controlling the reproduction frequency band of such a subwoofer, and is a pre-out volume circuit
having a variable resistor VR1 for a fader. 1 and a subwoofer-dedicated volume circuit 2 having a
variable resistor VR2. A control line 8 consisting of a DT line, a CK line, and an ST line to which a
control signal from a microcomputer (not shown) is input is connected to the volume circuit 1,
and a variable resistor is controlled by the control signal via the control line 8. When the
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resistance value of VR1 is changed, the input signal in the entire band is attenuated by a
predetermined amount and output from the pre-out terminal 4 through the pre-out amplifier 3.
[0004]
Further, a control line 9 consisting of a DT line, a CK line and an ST line is also connected to the
volume circuit 2, and similarly, when the resistance value of the variable resistor VR2 is changed
by the control signal from the microcomputer, The input signal in the entire band is attenuated
by a predetermined amount, and output from the subwoofer output terminal 7 via the amplifier 5
for subwoofer and the f special switching circuit 6. Here, the f special switching circuit 6 is for
switching the cutoff frequency of the subwoofer, and is constituted by an operational amplifier,
an analog switch, etc.
[0005]
However, in the above-described conventional signal pass band switching circuit, the volume
circuits 1 and 2 are separately provided for the pre-out and for the subwoofer, respectively, and
these volume circuits are also provided. Since 1 and 2 are controlled by control signals from the
microcomputer via control lines 8 and 9, attenuation level control for the input signal by the
microcomputer is complicated.
[0006]
Further, since the pre-out terminal 4 and the subwoofer output terminal 7 are separately
provided, the space can not be effectively utilized by the pre-out terminal 4 and the subwoofer
output terminal 7. is there.
[0007]
SUMMARY OF THE INVENTION The present invention has been made in view of such
circumstances, and it is an object of the present invention to provide a signal passband switching
circuit which has a simple configuration and can easily perform attenuation level control. .
[0008]
SUMMARY OF THE INVENTION In order to achieve the above object, the present invention
switches a signal passband for switching between a full band input signal and a low band for a
subwoofer of the input signal. In the switching circuit, an electronic volume for adjusting the
amount of attenuation of the level of the input signal in the entire band, a first amplifier for
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amplifying the input signal adjusted by the electronic volume by a predetermined amount, and
amplification by the first amplifier First switch means for capturing the pass band of the input
signal for each predetermined band, and second switch means for capturing the input signal of
the full bandwidth whose attenuation is adjusted by the electronic volume; A second amplifier for
amplifying an input signal acquired by the first switch means or the second switch means by a
predetermined amount; and the second switch means in an on state When the center position of
the electronic volume is in the initial state and the first switch means is in the on state, the
position where the apparent gain of the first amplifier of the electronic volume is lost is in the
initial state. And setting means for setting.
[0009]
In the signal pass band switching circuit according to the present invention, when the second
switch means is turned on by the setting means at the time of output of the input signal of the
entire band, the center of the electronic volume is set as the initial state. By varying the center
value, for example, fader operation can be performed.
[0010]
On the other hand, at the time of the output of the low band for the subwoofer, when the first
switch means is turned on, the position at which the apparent gain of the first amplifier of the
electronic volume disappears is taken as the initial state. By changing V, it is possible to perform
boost and cut operations of the output frequency.
[0011]
As a result, for example, the volume circuit 1 having the variable resistor VR1 for a fader, which
has been conventionally used, may be used as the volume circuit 2 having the variable resistor
VR2.
[0012]
Embodiments of the present invention will be described in detail with reference to the drawings.
In the drawings described below, the parts common to FIG.
[0013]
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FIG. 2 shows an embodiment of the signal pass band switching circuit according to the present
invention, which is provided with a volume circuit 1 having a variable resistor VR1 for a fader
which takes in an input signal of the entire band. .
The variable output of the variable resistor VR1 is connected to the subwoofer output terminal 7
via the amplifier 5 for subwoofer, the frequency & mode switching circuit 14 and the amplifier 3
for pre-out.
The subwoofer output terminal 7 also functions as a pre-out terminal.
[0014]
Gain setting resistors R1 and R2 for setting the gain of the amplifier 5 are connected to the
noninverting input terminal of the amplifier 5 for subwoofer.
The reference power supply Vref is input to the inverting input terminal of the amplifier 5.
[0015]
The frequency & mode switching circuit 14 is provided with resistors R3 to R8 connected in
parallel to the output end of the amplifier 5.
Grounding capacitors C4 to C6 are connected to the output side of the resistors R6 to R8.
Further, on the output side of the resistors R6 to R8, on / off switches SW1 to SW3 as first switch
means constituted by an IC are provided.
An on / off switch SW4 as a second switch means is connected between the volume circuit 1 and
the input end of the amplifier 5, and the variable resistor of the volume circuit 1 is turned on by
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turning on the on / off switch SW4. An input signal of the entire band attenuated by VR1 is taken
in.
[0016]
The output side of each of the on / off switches SW1 to SW4 is connected to the non-inverted
input terminal of the pre-out amplifier 3. Capacitors C1 to C3 are connected between the output
sides of the resistors R3 to R5 and the output end of the amplifier 3. The output of the amplifier
3 is taken into the inverting input terminal of the amplifier 3. Here, a low pass filter is constituted
by the resistors R3 to R8, the capacitors C1 to C6 and the amplifier 3.
[0017]
A control line 10 consisting of a DT line, a CK line, and an ST line is connected between the
volume circuit 1 and the system microcomputer 12. Further, between the frequency & mode
switching circuit 14 and the system microcomputer 12, a control line 11 composed of the SuB0
line and the SuB1 line is connected.
[0018]
Here, the selection signal from the system microcomputer 12 via the control line 11 is, for
example, pulse signals of "0" and "1" as shown in FIG. , 50 Hz, and off can be selected. That is, for
example, when the selection functions of 120HZ, 80HZ and 50HZ are provided for the respective
on / off switches SW1 to SW3, the resistance R6-capacitor C4 and the resistance R7-capacitor
C5, corresponding to the respective frequency bands A pass band value is set by the resistor R8capacitor C6.
[0019]
The system microcomputer 12 is connected via a signal line with a key input unit 13 for
instructing to switch between pre-out and subwoofer output, and instructing selection of a
reproduction output band at the time of sub-woofer output.
[0020]
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Subsequently, the operation of the subwoofer control circuit having such a configuration will be
described with reference to FIG.
First, when the setting input from the key input unit 13 is pre-out, the value of the volume circuit
1 is initialized to the center value. From this state, the value of the volume circuit 1 is
appropriately changed by the control signal from the system microcomputer 12 to perform fader
control.
[0021]
At this time, the control signals from the system microcomputer 12 to the frequency & mode
switching circuit 14 via the control line 11 are "1" and "1", and all the on / off switches SW1 to
SW3 are off. And the on / off switch SW4 is on
[0022]
Thus, when the input signal of the entire band attenuated by a predetermined amount by the
volume circuit 1 is taken into the amplifier 3 through the on / off switch SW4, after being
amplified by the amplifier 3, the subwoofer output terminal 7 (steps 401 to 403).
[0023]
On the other hand, when the setting input from the key input unit 13 is a subwoofer, first, setting
of the cutoff frequency in the frequency & mode switching circuit 14 is performed.
That is, when any of 120 Hz, 80 Hz and 50 Hz is set, "0", "0" or "0", "0", "1" or "1", "0" of the
control signal corresponding to these cutoff frequency bands. Is output to the frequency & mode
switching circuit 14 through the control line 11 from the system microcomputer 12, and one of
the on / off switches SW1 to SW3 corresponding to the control signal is turned on.
At this time, the on / off switch SW4 is in the off state.
[0024]
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Thus, the attenuation amount of the volume circuit 1 is appropriately changed by changing the
value from the initial value, whereby the input signal of the entire band attenuated by the
predetermined amount by the volume circuit 1 is amplified by the amplifier 5 and turned on. The
signal is taken into the amplifier 3 through one of the paths of the / off switches SW1 to SW3,
amplified by the amplifier 5, and then outputted from the subwoofer output terminal 7 (steps
404 to 406).
[0025]
As described above, in this embodiment, when the on / off switch SW4 is turned on by the
control signal from the system microcomputer 12 at the time of output of the input signal in the
entire band, the center of the electronic volume 1 is set as the initial state. By varying the center
value, for example, fader operation can be performed.
[0026]
On the other hand, at the time of the output of the low band for the subwoofer, when any of the
on / off switches SW1 to SW3 is turned on by the control signal from the system microcomputer
12, the appearance of the amplifier 5 of the electronic volume 1 is apparent. By changing this
position with the position where the gain of L disappears as the initial state, the boost and cut
operation of the output frequency can be performed.
[0027]
As a result, for example, since the volume circuit 1 having the variable resistor VR1 for a fader,
which has been conventionally used, can be used also as the volume circuit 2 having the variable
resistor VR2, attenuation level control is easy. Become.
Further, since the subwoofer output terminal 7 also functions as a pre-out terminal, only one subwoofer output and one pre-out terminal can be provided, so that the installation space of the
terminal can be effectively used.
[0028]
As described above, according to the signal pass band switching circuit of the present invention,
when the input signal of the entire band is output, the second switch means is turned on by the
setting means. The fader operation can be performed, for example, by varying the center value
with the center of the electronic volume as the initial state.
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[0029]
On the other hand, at the time of the output of the low band for the subwoofer, when the first
switch means is turned on, the position at which the apparent gain of the first amplifier of the
electronic volume disappears is taken as the initial state. By changing V, it is possible to perform
boost and cut operations of the output frequency.
[0030]
As a result, for example, since the volume circuit 1 having the variable resistor VR1 for a fader,
which has been conventionally used, can be shared by the volume circuit 2 having the variable
resistor VR2, the configuration can be simplified. Attenuation level control can be performed
easily.
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