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DESCRIPTION JP2016152418

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DESCRIPTION JP2016152418
Abstract: To prevent reflection of digital signals on the side of a speaker (receiving end)
regardless of the impedance of the speaker cable. A signal receiving apparatus 2 receives a
digital signal output from a digital amplifier 100 via a speaker cable 200, and outputs the
received digital signal to a speaker 3. The signal reception device 2 includes a variable resistor
R1 connected in parallel to the speaker 3, a detection unit 4 that half-wave rects the received
digital signal and outputs an average value of the half-wave rectified digital signal, and a
detection unit A display unit 5 for displaying the average value output by 4 and an operation
knob 6 for adjusting the resistance value of the variable resistor R1. [Selected figure] Figure 1
Signal receiving device and speaker device
[0001]
The present invention relates to a signal receiving apparatus that receives a digital signal output
from a digital amplifier such as a switching amplifier that amplifies an input signal such as an
audio signal and outputs the digital signal to a speaker, and a speaker apparatus.
[0002]
BACKGROUND A digital amplifier such as a switching amplifier that amplifies an input signal
such as an audio signal is known.
The digital amplifier performs pulse width modulation (Pulse Wide Modulation) on an input
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audio signal, for example, and outputs a digital signal such as a PWM signal which has been
pulse width modulated to a low pass filter. The low pass filter cuts high frequency components of
the digital signal and outputs it to the speaker. The speaker outputs voice based on the signal
output from the low pass filter. Here, if the digital signal output from the digital amplifier can be
output to the speaker without passing through the low pass filter, the high frequency component
of the audio signal can be reproduced by the speaker. In addition, since the low pass filter is not
necessary, the cost of the digital amplifier is reduced, and the size of the digital amplifier is
reduced.
[0003]
However, when the digital amplifier and the speaker are connected by the speaker cable, if the
impedance of the speaker cable and the impedance on the speaker side do not match, the high
frequency component of the digital signal is reflected on the speaker (receiving end) side , There
is a problem that the waveform of the digital signal is ringing. In the devices described in Patent
Documents 1 and 2, as shown in FIG. 8, a resistor R is provided on the speaker 300 (receiving
end) side so that the impedance on the speaker 300 side matches the impedance of the speaker
cable 400. For example, if the impedance of the speaker cable is 70Ω, a 70Ω resistor R may be
provided. As a result, the high frequency component of the digital signal output from the digital
amplifier 500 (transmission end) side is absorbed by the resistor R on the speaker 300
(reception end) side and is not reflected.
[0004]
Japanese Patent Application Laid-Open No. 6-189391 Japanese Patent Application Laid-Open No.
6-292295
[0005]
The speaker cable connected to the digital amplifier and the speaker cable has different
impedance depending on the product.
Therefore, the devices described in Patent Literatures 1 and 2 have a problem that they can not
cope with speaker cables of different impedances.
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2
[0006]
An object of the present invention is to prevent the reflection of digital signals on the side of the
speaker (receiving end) regardless of the impedance of the speaker cable.
[0007]
A signal receiving apparatus according to a first aspect of the present invention is a signal
receiving apparatus that receives a digital signal output from a digital amplifier via a speaker
cable and outputs the received digital signal to a speaker, and is connected in parallel to the
speaker A variable resistor, a detection unit that half-wave rects the received digital signal and
outputs an average value of the half-wave rectified digital signal, a display unit that displays the
average value output from the detection unit, and the variable And a first adjustment unit for
adjusting the resistance value of the resistor.
[0008]
In the present invention, the display unit displays the average value of the digital signal output
from the detection unit.
In addition, the user can adjust the resistance value of the variable resistor connected in parallel
to the speaker by the first adjusting unit.
Therefore, the user adjusts the resistance value of the variable resistor by the first adjustment
unit so that the average value displayed on the display unit becomes the voltage value (peak
value) of the digital signal output from the digital amplifier. The impedance of the speaker cable
connected between the digital amplifier and the speaker can be matched with the impedance of
the speaker (receiving end). This prevents the reflection of digital signals on the speaker
(receiving end) side. Thus, according to the present invention, it is possible to prevent the
reflection of digital signals on the side of the speaker (receiving end) regardless of the impedance
of the speaker cable.
[0009]
A signal receiving apparatus according to a second aspect of the present invention is the signal
receiving apparatus according to the first aspect, further comprising a second adjusting unit for
adjusting the voltage value of the reference voltage, and the display unit includes the voltage
value of the reference voltage. A difference from the average value is displayed.
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[0010]
In the present invention, the display unit displays the difference between the voltage value of the
reference voltage and the average value.
Therefore, the user can easily adjust the impedance of the speaker cable and the impedance on
the speaker side by adjusting the first adjustment unit so that the difference between the voltage
value of the reference voltage and the average value disappears while checking the display unit.
Can be matched.
[0011]
A signal receiving apparatus according to a third aspect of the present invention is the signal
receiving apparatus according to the second aspect, wherein the display unit is an analog
voltmeter having a needle that rotates about a voltage value of the reference voltage and displays
the difference. And the needle rotates counterclockwise to display the difference when the
difference is negative, and rotates clockwise to display the difference when the difference is
positive. It is characterized by
[0012]
In the present invention, the display unit is an analog voltmeter.
For this reason, there is no need to provide a separate power supply to display the average value.
In addition, the user can easily adjust the impedance of the speaker cable and the impedance on
the speaker side by adjusting the first adjustment unit so that the difference between the voltage
value of the reference voltage and the average value disappears while confirming the needle. It
can be put together.
[0013]
A signal receiving apparatus according to a fourth aspect of the present invention is the signal
receiving apparatus according to any of the first to third aspects, wherein the detection unit is a
diode that half-wave rectifies the digital signal output by the digital amplifier; And a first
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capacitor connected in series with the resistor, wherein the diode integrates the half-rectified
digital signal and outputs an average value.
[0014]
According to the present invention, it is possible to make the detection part a simple circuit
configuration by an integration circuit having a diode, a resistor and a capacitor.
[0015]
A signal receiving apparatus according to a fifth aspect of the present invention is the signal
receiving apparatus according to any of the first to fourth aspects, further comprising a second
capacitor connected in series to the variable resistor.
[0016]
In the present invention, the second capacitor is connected in series to the variable resistor.
Therefore, current consumption by the variable resistor can be significantly reduced.
[0017]
According to a sixth aspect of the present invention, there is provided a speaker device according
to any one of the first to fifth aspects, including the signal receiving device according to any one
of the first to fifth aspects and a speaker. It features.
[0018]
According to the present invention, it is possible to prevent reflection of digital signals on the
speaker (receiving end) side regardless of the impedance of the speaker cable.
[0019]
It is a figure showing basic composition of a speaker apparatus concerning an embodiment of the
present invention.
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6 shows a specific circuit configuration of the speaker device according to the present
embodiment.
(A) is a front view which shows the external appearance of the speaker apparatus which concerns
on this embodiment.
(B) is a rear view which shows the external appearance of the speaker apparatus based on this
embodiment.
(A) is a graph which shows the digital signal for a test output from a digital amplifier. (B) is a
graph which shows the digital signal in the speaker side. (C) is a graph which shows the average
value of a digital signal. (A) is a graph which shows the digital signal for a test output from a
digital amplifier. (B) is a graph which shows the digital signal in the speaker side. (C) is a graph
which shows the average value of a digital signal. (A) is a graph which shows the digital signal for
a test output from a digital amplifier. (B) is a graph which shows the digital signal in the speaker
side. (C) is a graph which shows the average value of a digital signal. (A) is a side view which
shows the external appearance of the signal receiver which concerns on a modification, and a
speaker. (B) is a rear view of the signal receiving device concerning a modification. It is a figure
showing the circuit composition of the conventional device.
[0020]
Hereinafter, embodiments of the present invention will be described. FIG. 1 is a view showing a
basic configuration of a speaker device according to an embodiment of the present invention.
The speaker device 1 includes a signal receiving device 2 that receives a digital signal output
from the digital amplifier 100 and outputs the digital signal to the speaker 3, and the speaker 3.
The digital amplifier 100 and the speaker device 1 (speaker 3) are connected by a speaker cable
200.
[0021]
The digital amplifier 100 performs pulse width modulation on the input audio signal, and outputs
the pulse width modulated audio signal (digital signal) to the signal receiving device 2. Here, the
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digital amplifier 100 exemplifies pulse width modulation of the audio signal. However, the
present invention is not limited to this, and the digital amplifier 100 may output the digital signal
to the signal reception device 2. For example, the digital amplifier 100 may perform pulse
density modulation on an audio signal and output the signal to the signal receiving device 2.
[0022]
The signal receiving device 2 includes a variable resistor R1, a capacitor C1, a detection unit 4, a
display unit 5, an operation knob 6, and a slider 7. The variable resistor R1 is connected in
parallel to the speaker 3. The resistance value of the variable resistor R1 can be changed by an
operation knob 6 described later. The capacitor C1 (second capacitor) is connected in series to
the variable resistor R1. One end of the capacitor C1 is connected to the variable resistor R1, and
the other end is connected to the ground potential.
[0023]
The detection unit 4 half-wave rectifies the digital signal output from the digital amplifier 100,
and outputs an average value of the half-end rectified digital signal. FIG. 2 is a diagram showing a
specific circuit configuration of the speaker device according to the present embodiment. As
illustrated, the detection unit 4 includes a diode D1 and an integration circuit 8. The diode D1
half-end rectifies the digital signal output from the digital amplifier 100. The anode of the diode
D1 is connected to the other end of the resistor R2 constituting the integration circuit 8. The
cathode of the diode D1 is connected to the positive electrode terminal of the display unit 5
(analog voltmeter). The integration circuit 8 integrates the digital signal half rectified by the
diode D1 and outputs an average value of the digital signal. The integrating circuit 8 includes a
resistor R2 and a capacitor C2 (first capacitor) connected in series to the resistor R2. One end of
the resistor R2 is connected between the speaker 3 and the variable resistor R1. The other end of
the resistor R2 is connected to the anode of the diode D1. The capacitor C2 is connected between
the positive pole terminal of the display unit 5 (analog voltmeter) and a terminal connected to the
negative pole terminal of the display unit 5 (analog voltmeter). The resistor R3 is connected
between the positive terminal of the display unit 5 (analog voltmeter) and a terminal connected
to the negative terminal of the display unit 5 (analog voltmeter). The resistor R3 is in parallel
with the capacitor C2, and is a resistor for discharging the capacitor C2.
[0024]
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The display unit 5 displays the average value of the digital signal output from the detection unit
4. Specifically, the display unit 5 is an analog voltmeter. The display unit 5 includes a meter 9
and a magnification unit 10. FIG. 3 is a view showing the appearance of the speaker device,
where (a) is a front view and (b) is a rear view. As shown in FIG. 3 (b), the meter 9 is provided on
the back of the housing of the speaker device 1. In addition, the meter 9 has a needle 11 for
displaying the average value of the digital signal. In FIG. 2, the resistance R V indicates the
internal resistance of the meter 9.
[0025]
The multiplier 10 is for changing the voltage value of the reference voltage displayed by the
meter 9 and has resistors R M1, R M2 and R M3. For example, when the terminal of the detection
unit 4 is connected to the negative terminal including all of the resistors R M1 to R M3 of the
display unit 5 (the multiplier 10), the voltage value of the reference voltage is 60V. When the
terminal of the detection unit 4 is connected to the negative terminal including R M2 and R M3
of the display unit 5 (multiplier 10), the voltage value of the reference voltage is 50V. In addition,
when the terminal of the detection unit 4 is connected to the negative electrode terminal
including only R M3 of the display unit 5 (multiplier 10), the voltage value of the reference
voltage is 25V. In addition, when the terminal of the detection unit 4 is connected to the negative
electrode terminal that does not include all the resistors R M1 to R M3 of the display unit 5
(multiplier 10), the voltage value of the reference voltage is 20V. The selection of which negative
terminal of the display unit 5 (the magnification unit 10) the terminal of the detection unit 4 is to
be connected to, ie, the selection of the voltage value of the reference voltage is performed by the
slider 7 described later.
[0026]
Here, the needle 11 of the meter 9 rotates the difference between the voltage value of the
reference voltage set by the magnification device 10 and the average value output from the
detection unit 4 around the voltage value of the reference voltage and displays it Do. Specifically,
when the difference is negative, the needle 11 rotates counterclockwise to display the difference.
Further, when the difference is positive, the needle 11 rotates clockwise to display the difference.
[0027]
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The operation knob 6 (first adjustment unit) is for adjusting the resistance value of the variable
resistor R1. As shown in FIG. 3 (b), the operation tab 6 is provided on the back of the housing of
the speaker device 1. The operation knob 6 is rotatable clockwise and counterclockwise, and the
resistance value of the variable resistor R1 can be adjusted so that the resistance value increases
in the clockwise direction. For example, the operation knob 6 can adjust the resistance value of
the variable resistor R1 from a minimum of 10 Ω to a maximum of 300 Ω. The slider 7 (second
adjusting unit) is for adjusting the voltage value of the reference voltage displayed on the display
unit 5. As shown in FIG. 3 (b), the slider 7 is provided on the back of the housing of the speaker
device 1. The slider 7 is slidable in the left-right direction, and the voltage value of the reference
voltage can be adjusted so that the voltage value increases in the right direction. The user can
adjust the voltage value of the reference voltage to that voltage value by moving the slider 7 to
the position displayed as 20V, 25V, 50V, 60V. Here, when the slider 7 is moved to the position of
each voltage value, the terminal of the detection unit 4 is connected to the negative electrode
terminal of the display unit 5 (the magnification unit 10) according to the voltage value. For
example, when the slider 7 is moved to the position of the voltage value 60 V, the terminal of the
detection unit 4 is connected to the negative electrode terminal including all the resistors R M1
to R M3 of the display unit 5 (the magnification unit 10). As shown in FIG. 3B, connection
terminals (+,-) 12, 13 for connecting the speaker cable 200 are provided on the back of the
housing of the speaker device 1.
[0028]
In FIG. 2, an equivalent circuit of the speaker 3 is shown by the coil L1, the capacitor C3, and the
resistors R4 and R5.
[0029]
Next, the case where a digital signal is output from the digital amplifier 100 to the speaker device
1 will be described.
For example, as shown in FIG. 4A, a digital signal (pulse signal) for test with a voltage value (peak
value) ± 20 V and a duty ratio of 50% is output from the digital amplifier 100 to the speaker
device 1. Here, it is assumed that the impedance of the speaker cable 200 is 100Ω, the
impedance on the speaker 3 side is 200Ω, and the impedance on the speaker 3 side is large.
Then, since the impedance of the speaker cable 200 and the impedance of the speaker 3 do not
match, the digital signal is reflected on the speaker 3 side. At this time, since the impedance on
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the side of the speaker 3 is too large compared to the impedance of the speaker cable 200, the
reflected signal becomes positive, and a positive reflected signal as a digital signal as shown by
an elliptically enclosed portion in FIG. Is added.
[0030]
FIG. 4C shows the average value of the signals obtained by half-wave rectifying the signals shown
in FIG. 4B and half-wave rectifying, that is, the output of the detection unit 4. Since the positive
reflection signal is added to the digital signal, the average value is 33.7 V, which is larger than
the voltage value 20 V of the digital signal.
[0031]
Further, for example, as shown in FIG. 5A, a digital signal (pulse signal) for test is output from the
digital amplifier 100 to the speaker device 1. Here, it is assumed that the impedance of the
speaker cable 200 is 100Ω, the impedance of the speaker 3 is 50Ω, and the impedance of the
speaker 3 is small. Then, since the impedance of the speaker cable 200 and the impedance of the
speaker 3 do not match, the digital signal is reflected on the speaker 3 side. At this time, since
the impedance on the side of the speaker 3 is too small compared to the impedance of the
speaker cable 200, the reflected signal becomes negative, and a negative reflected signal as a
digital signal as shown in the portion enclosed by an ellipse in FIG. Is added.
[0032]
FIG. 5C shows the average value of the signals obtained by half-wave rectifying the signals shown
in FIG. 5B and half-wave rectifying, that is, the output of the detection unit 4. Since the negative
reflection signal is added to the digital signal, the average value is 14.9 V, which is smaller than
the voltage value 20 V of the digital signal.
[0033]
Also, for example, as shown in FIG. 6A, a digital signal (pulse signal) for test is output from the
digital amplifier 100 to the speaker device 1. Here, it is assumed that the impedance of the
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speaker cable 200 is 100Ω and the impedance of the speaker 3 is 100Ω, and the impedance of
the speaker cable 200 matches the impedance of the speaker 3. Then, since the impedance of the
speaker cable 200 matches the impedance of the speaker 3 side, the digital signal is not reflected
on the speaker 3 side. Therefore, as shown in FIGS. 4 (b) and 5 (b), since the reflected signal is
not added to the digital signal, the waveform is as shown in FIG. 6 (b), and the voltage value is
approximately ± 20 V. .
[0034]
FIG. 6C shows an average value of the signals obtained by half-wave rectifying the signals shown
in FIG. 6B and half-wave rectifying, that is, the output of the detection unit 4. Since the reflection
signal is not added to the digital signal, the average value is 19 V, which is substantially the same
as the voltage value 20 V of the digital signal.
[0035]
In this embodiment, since the resistance value of the variable resistor R1 can be adjusted by the
operation knob 6, the voltage value (peak value) of the test digital signal (pulse signal) output
from the digital amplifier 100, and the detection unit If the resistance value of the variable
resistor R1 is adjusted so that the average value output by 4 matches, the impedance of the
speaker cable 200 and the impedance on the speaker 3 (receiving end) side can be matched.
Here, the display unit 5 displays the difference between the voltage value of the reference
voltage set by the multiplying device 10 and the average value output from the detection unit 4
with the needle 11. Therefore, if the user selects the voltage value of the reference voltage set by
the multiplier 10 as the voltage value of the digital signal output by the digital amplifier 100
using the slider 7, the voltage value of the reference voltage and the detection unit 4 The
impedance of the speaker cable 200 and the impedance on the speaker 3 (receiving end) side are
adjusted by adjusting the operation knob 6 so that the difference between the average value
output by And can be combined.
[0036]
In the speaker device 1 configured as described above, a procedure for matching the impedance
of the speaker cable 200 with the impedance of the speaker 3 (receiving end) will be described.
First, the user uses the slider 7 to select the voltage value of the reference voltage displayed on
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the display unit 5. Here, the user selects the voltage value (peak value) of the digital signal (pulse
signal) output from the digital amplifier 100 using the slider 7. Thus, the needle 11 rotates
around the voltage value (peak value) of the digital signal (pulse signal) output from the digital
amplifier 100. The voltage value of the digital signal output from the digital amplifier 100 varies
depending on the model.
[0037]
Next, the user causes the digital amplifier 100 to output a test digital signal (pulse signal) as
shown in FIGS. 4 (a), 5 (a), and 6 (a). For example, the digital amplifier 100 has a test mode for
matching the impedance, and outputs a digital signal for test by being set in the test mode.
[0038]
Next, the user operates the operation knob 6 so that the needle 11 is centered while checking the
meter 9. Thereby, the impedance of the speaker cable 200 and the impedance on the speaker 3
(receiving end) side can be matched.
[0039]
As described above, in the present embodiment, the display unit 5 displays the average value of
the digital signals output from the detection unit 4. In addition, the user can adjust the resistance
value of the variable resistor R1 connected in parallel to the speaker 3 by the operation knob 6.
Therefore, the user adjusts the resistance value of the variable resistor R1 with the operation
knob 6 so that the average value displayed on the display unit 5 becomes the voltage value (peak
value) of the digital signal output from the digital amplifier 100. Thus, the impedance of the
speaker cable 200 connected between the digital amplifier 100 and the speaker 3 can be
matched with the impedance of the speaker 3 (receiving end). Thereby, reflection of the digital
signal at the speaker 3 (receiving end) side is prevented. Thus, according to the present
invention, regardless of the impedance of the speaker cable 200, it is possible to prevent the
reflection of digital signals on the side of the speaker 3 (receiving end).
[0040]
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Further, in the present embodiment, the display unit 5 displays the difference between the
voltage value of the reference voltage and the average value. Therefore, the user can easily adjust
the impedance of the speaker cable 200 and the speaker 3 side by adjusting the operation knob
6 so that the difference between the voltage value of the reference voltage and the average value
disappears while checking the display unit 5. Can be matched with the impedance of
[0041]
Moreover, in the present embodiment, the display unit 5 is an analog voltmeter. For this reason,
there is no need to provide a separate power supply to display the average value. Also, the user
can easily adjust the impedance of the speaker cable 200 and the impedance of the speaker 3 by
adjusting the operation knob 6 so that the difference between the voltage value of the reference
voltage and the average value disappears while checking the needle 11 Can be matched.
[0042]
Further, in the present embodiment, the detection unit 4 is configured by the integrating circuit 8
having the diode D1, the resistor R2, and the capacitor C2, and thus has a simple circuit
configuration.
[0043]
Further, in the present embodiment, the capacitor C1 is connected in series to the variable
resistor R1.
Therefore, current consumption by the variable resistor R1 can be significantly reduced.
[0044]
As mentioned above, although embodiment of this invention was described, the form which can
apply this invention is not restricted to the above-mentioned embodiment, As it illustrates below,
it is suitably in the range which does not deviate from the meaning of this invention. It is possible
to make changes.
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[0045]
In the above-described embodiment, the signal receiving device 2 and the speaker 3 are provided
in the same housing, and the speaker device 1 is configured by the signal receiving device 2 and
the speaker 3.
Not limited to this, the signal receiving device 2 and the speaker 3 may be provided in different
cases. FIG. 7A is a side view showing an appearance of the signal receiving device 2 and the
speaker 3 in an example in which the signal receiving device 2 and the speaker 3 are provided in
different housings. FIG. 7B is a rear view of the signal receiving apparatus. As shown in FIG. 7B,
on the rear face of the case of the signal receiving device 2, an operation tab 6, a slider 7, a meter
9, and connection terminals 12 and 13 are provided.
[0046]
In the above embodiment, the capacitor C1 is connected in series to the variable resistor R1, but
the capacitor C1 may not be provided.
[0047]
In the above-described embodiment, the display unit 5 exemplifies the case of an analog
voltmeter.
Not only this but the display part 5 may be a digital voltmeter, for example.
[0048]
In the above embodiment, the operation knob 6 is illustrated as one for adjusting the resistance
value of the variable resistor R1. Not limited to this, for example, it may be a slider or the like in
which the resistance value of the variable resistor R1 changes by sliding linearly. Moreover, the
slider 7 was illustrated as a thing for adjusting the voltage value of a reference voltage. Not
limited to this, for example, it may be an operation knob or the like in which the voltage value of
the reference voltage is changed by rotating.
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[0049]
The present invention can be suitably adopted in a signal receiving apparatus that receives a
digital signal output from a digital amplifier such as a switching amplifier that amplifies an input
signal such as an audio signal and outputs the digital signal to a speaker, and a speaker
apparatus.
[0050]
Reference Signs List 1 speaker device 2 signal reception device 3 speaker 4 detection unit 5
display unit 6 operation knob (first adjustment unit) 7 slider (second adjustment unit) 8
integration circuit 9 meter 10 magnification unit 11 needle
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