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DESCRIPTION JP2003249824

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DESCRIPTION JP2003249824
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
output amplification apparatus and an audio system for reproducing sound such as an audio
system, and more particularly to an output amplification apparatus and an audio system for
suitably connecting the output amplification apparatus and a speaker apparatus. .
[0002]
In the field aiming at high fidelity music reproduction such as the so-called high-end audio
system in recent years, the connection method between the output amplification device and the
speaker device is a problem, and It is said that the sound quality is significantly affected by the
material, shape, and connection method. Therefore, using oxygen free copper as a material of a
connecting cable, using an expensive connecting cable processed into a special shape is carried
out.
[0003]
In addition, when the speaker device is composed of a high sound speaker and a low sound
speaker, the output amplification device and the speaker device are connected by a pair of
common connection cables, and the high sound and low sound speakers are sounded inside the
speaker device. When the signals are distributed, the back electromotive force of each speaker
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1
may wrap around the other speaker through the common connection cable, which may adversely
affect the sound quality. Therefore, in recent years, a method called bi-wiring has often been
adopted in which the output amplification device and the high sound speaker and between the
output amplification device and the low frequency speaker are connected by separate connection
cables. However, when using this bi-wiring method, it is necessary to double the expensive
connection cable.
[0004]
By the way, when viewed from the output amplification device, the connection cable has a certain
impedance, has a low driving impedance, and has a surface that is not suitable for driving a
complicatedly changing speaker device. With impedance, as described above, back electromotive
force interference may occur. Thus, the relevance of using a low impedance connection cable or
even using a bi-wiring approach can be explained to some extent.
[0005]
However, as a practical matter, although there is no specific, quantitative, or explicit illustration
as to how much influence is given to a complex changing music signal, highly subjective
judgments and evaluations In this field of entry, it is pointed out that the problems described
above are raised and that the sound quality is different, and as a result, expensive connection
cables are put into practical use and used. Ideally, the distance between the output amplification
device and the speaker device is desirably zero, and although a speaker system incorporating the
output amplification device has been proposed, this is not necessarily general.
[0006]
Hereinafter, the prior art will be described with reference to the drawings. First, the principle of
negative feedback of the output amplification device will be described.
[0007]
FIG. 6 is a connection configuration diagram of a simple output amplification device without a
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2
negative feedback and a speaker device. In FIG. 6, the output amplification device PA and the
speaker device SS (loads of the output amplification device PA, and so on). ) Are mutually
connected by connection cables Ca and Cb. The output amplification device PA includes input
terminals IT0 and IT1, an amplification circuit A, an output transformer T, and output terminals
OT0 and OT1.
[0008]
The input terminals IT0 and IT1 are connected to the input terminal of the amplifier circuit A,
and the output terminal of the amplifier circuit A is connected to the primary side terminal of the
output transformer T. Furthermore, the secondary terminals of the output transformer T are
connected to the output terminals OT0 and OT1. The input terminal IT1 and the output terminal
OT1 are connected to the ground, respectively.
[0009]
Further, the speaker device SS includes input terminals S0 and S1 and a speaker unit SU. The
input terminals S0 and S1 are connected to the speaker unit SU. The output terminal OT0 and the
input terminal S0 are connected by the connection cable Ca, and the output terminal OT1 and the
input terminal S1 are connected by the connection cable Cb, and the output amplification device
PA and the speaker device SS are connected to each other. Is configured.
[0010]
In the connection configuration diagram shown in FIG. 6, the input voltage applied between the
input terminal IT0 and the input terminal IT1 is ei, the output voltage appearing between the
output terminal OT0 and the output terminal OT1 is eo, and the amplification degree of the
amplifier circuit A Assuming that a, the following equation 1 holds.
[0012]
Although the amplification factor a is a value determined by the internal configuration of the
amplifier circuit A and the output transformer T, it is not usually a constant value for the input
voltage value, frequency, etc., and it is an output for the input voltage ei It appears as distortion
of voltage eo.
10-04-2019
3
[0013]
FIG. 7 is a connection configuration diagram of an output amplification device to which negative
feedback is applied and a speaker device.
Hereinafter, the difference from the configuration of the output amplifier without negative
feedback shown in FIG. 6 will be described with reference to FIG.
[0014]
In FIG. 7, a resistor R1 is inserted between the output terminal OT0 and the ground-side input
terminal of the amplifier circuit A.
Further, a resistor R2 is inserted between the input terminal IT0 and the ground-side input
terminal of the amplifier circuit A, and one terminal of the resistor R1 is connected to a
connection portion between the resistor R2 and the input terminal of the amplifier circuit A. . In
this manner, a part of the output voltage eo appearing between the output terminal OT0 and the
output terminal OT1 is returned to the input side of the amplifier circuit A by the resistors R1
and R2 constituting the negative feedback circuit.
[0015]
In the connection configuration diagram shown in FIG. 7, an input voltage applied between the
input terminal IT0 and the input terminal IT1 is ei, an output voltage appearing between the
output terminal OT0 and the output terminal OT1 is eo, Assuming that a is, the following number
2 is established.
[0017]
【0017】ここで、
[0019]
Then, the following equation 4 is derived from the equations 2 and 3;
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4
[0021]
From the equation 4, the following equation 5 is established.
[0023]
Therefore, assuming that a is a sufficiently large value (for example, 100), the amplification
factor af when the negative feedback is applied is determined by the following equation (6).
[0025]
Strictly speaking, the input voltage ei is attenuated by the resistor R2 before being applied to the
amplifier circuit A. However, since the input impedance of the amplifier circuit A can usually be
designed sufficiently large, this attenuation can be ignored.
Further, since this attenuation is a matter not related to the essence of the present invention,
hereinafter, the input impedance of the amplification circuit A will be described as infinite.
[0026]
Furthermore, although the value of the amplification degree a is set to 100 as an example, this is
a general value.
Assuming that resistors R1 and R2 are 9 k ohms and 1 k ohms, respectively, the amplification
factor af is 10, and the amplification factor at negative feedback is reduced to 1/10 that in the
absence of negative feedback. It is.
[0027]
Thus, the amplification degree af is a value determined only by the division ratio m simply by
resistance, and does not include non-linear elements.
Therefore, the distortion of the output is greatly reduced in the output amplification device
10-04-2019
5
subjected to negative feedback.
[0028]
As described above, in the output amplification apparatus to which negative feedback is applied,
distortion of the output is greatly reduced, but the input terminal of the speaker apparatus when
the speaker apparatus is actually driven Unlike the output voltage eo appearing between the
output terminal OT0 and the output terminal OT1 of the output amplification device PA, the
input voltage es between S0 and the input terminal S1 is changed by the influence of the
connecting cables Ca and Cb. Will occur.
[0029]
It is an object of the present invention to provide an audio system in which a negative feedback
signal is connected between an output amplification device and a speaker device with a
connection cable, a detection source of a negative feedback signal and an output voltage of the
output amplification device not eo of the speaker device By providing a connection configuration
in which the following equation 7 is satisfied, where voltage es is used, the input voltage ei of the
output amplification device and the input voltage es of the speaker device are in a linear
relationship, and the influence of the connection cable is not affected. It is an object of the
present invention to provide an output amplification device and an acoustic system in which the
distance between the output amplification device and the speaker device is equivalently made
zero.
[0031]
According to the present invention, in an output amplification apparatus for connecting a load
input terminal with a connection cable and driving the load, the input terminal, an output
terminal for connecting the load, and the input terminal. The amplifier circuit amplifies the signal
applied to the circuit and sends it to the output terminal, the negative feedback terminal
connecting the input terminal of the load with another connection cable, and the signal applied to
the negative feedback terminal And a negative feedback circuit for applying negative feedback to
the amplification circuit.
[0032]
Further, according to the present invention, in the acoustic system including a load having an
input terminal and an output amplification device for driving the load, the output amplification
device is connected to the input terminal of the load by an input terminal and a first connection
cable. An output terminal to be connected, an amplification circuit for amplifying a signal applied
to the input terminal and transmitting the amplified signal to the output terminal, and a negative
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6
feedback terminal connected to the input terminal of the load by a second cable And a negative
feedback circuit that applies negative feedback to the amplification circuit according to a signal
applied to the negative feedback terminal, and a signal at an input terminal of the load is a
negative feedback signal of the output amplification device. I assume.
[0033]
BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be
described below with reference to the drawings.
[0034]
FIG. 1 is a connection configuration diagram of an output amplification device and a speaker
device according to a first embodiment of the present invention.
[0035]
In FIG. 1, the output amplification device PA and the speaker device SS are connected to each
other by connection cables Ca, Cb, Cc and Cd.
The output amplifier PA includes input terminals IT0 and IT1, an amplifier circuit A, an output
transformer T, a resistor R1, a resistor R2, output terminals OT0 and OT1, and negative feedback
input terminals OT2 and OT3. There is.
[0036]
The input terminal IT0 is connected to one input terminal of the amplifier circuit A, and the input
terminal IT1 is connected to one end of the resistor R2 and the ground, and the other end of the
resistor R2 is connected to the amplifier circuit A. It is connected to the other input terminal.
[0037]
The output terminal of the amplifier circuit A is connected to the primary side terminal of the
output transformer T.
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Further, the secondary side terminals of the output transformer T are connected to the output
terminals OT0 and OT1.
Furthermore, one end of the resistor R1 is connected to the connection point between the other
end of the resistor R2 and the other input terminal of the amplifier circuit A, and the other end of
the resistor R1 is connected to the negative feedback input terminal OT2.
The negative feedback input terminal OT3 is connected to the ground.
[0038]
Further, the speaker device SS includes input terminals S0 and S1, negative feedback output
terminals S2 and S3, and a speaker unit SU.
The input terminals S0 and S1 are connected to the speaker unit SU, and the negative feedback
output terminals S2 and S3 are directly connected to the input terminals S0 and S1, respectively.
[0039]
The output terminal OT0 and the input terminal S0 are connected by the connecting cable Ca,
the output terminal OT1 and the input terminal S1 are connected by the connecting cable Cb,
and the negative feedback input terminal OT2 and the negative feedback output terminal S2 are
connected by the connecting cable Cc. The negative feedback input terminal OT3 and the
negative feedback output terminal S3 are connected by the connection cable Cd, and the output
amplification device PA and the speaker device SS are connected to each other.
[0040]
Hereinafter, the operation of the connection configuration shown in FIG. 1 will be described.
[0041]
According to the connection configuration shown in FIG. 1, the negative feedback in the output
amplification device PA is not due to the output voltage eo appearing between the output
terminal OT0 and the output terminal OT1 of the output amplification device PA, but the input
terminal S0 of the speaker device It will be multiplied by the input voltage es between the
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terminals S1.
[0042]
Since the connection cables Ca and Cb drive speakers having an impedance of, for example,
several ohms, the influence of the connection cables Ca and Cb themselves is regarded as a
problem.
However, since resistance R1 and resistance R2 are usually selected to be, for example, 9 k ohm
and 1 k ohm respectively, the influence of connecting cables Cc and Cd having an impedance of
about 1 ohm or less is due to negative feedback. It can be ignored as a connection.
Therefore, assuming that the amplification degree of the amplifier circuit A is a, the following
equation 8 is established.
[0044]
【0044】ここで、
[0046]
Assuming that the following equation 10 is derived from the equations 8 and 9,
[0048]
From the equation (10), the following equation (11) is established.
[0050]
Here, assuming that a is a sufficiently large value (for example, 100), the amplification factor af
when negative feedback is applied is determined by the number 7 shown above, and the voltage
es is the connection cable Ca and It is not affected by Cb.
[0051]
As described above, when the negative feedback is returned from the terminal of the speaker
device SS, the influence of the connection cables Ca and Cb can be eliminated in principle.
10-04-2019
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[0052]
However, in FIG. 1, when either or both of the connection cables Cc and Cd are disconnected, the
negative feedback is not applied at all, and the amplification degree of the input voltage ei with
respect to the output voltage es is a.
Therefore, since a large output is produced even for a very small input signal ei, a loud sound
may be emitted from the speaker apparatus SS, and furthermore, the speaker apparatus SS may
be damaged.
Furthermore, when even one or both of the connection cables Ca and Cb are disconnected, the
output amplification device PA having a large amplification factor a becomes no load, no
feedback, causes oscillation, amplifies large noise and amplifies the amplification circuit There is
a possibility of causing a failure such as breakage of the A or the output transformer T.
[0053]
Therefore, a second embodiment for solving these problems will be described next.
[0054]
FIG. 2 is a connection configuration diagram of an output amplification device and a speaker
device according to a second embodiment of the present invention.
[0055]
The connection configuration shown in FIG. 2 solves the problem in the connection configuration
shown in FIG.
Hereinafter, differences from the configuration of the output amplification device shown in FIG. 1
will be described with reference to FIG.
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A resistor R3 is connected between the output terminal OT0 and the negative feedback input
terminal OT2, and a resistor R4 is connected between the output terminal OT1 and the negative
feedback input terminal OT3.
[0056]
The resistors R3 and R4 have the same value, and these values are sufficiently larger than the
sum Zf of the impedances of the connecting cables Cc and Cd and smaller than the resistor R1.
The reason for making the resistance value of the resistors R3 and R4 larger than the sum Zf of
the impedances of the connecting cables Cc and Cd is that the eo between the negative feedback
input terminal OT2 and the negative feedback input terminal OT3 is Zf and R3 + R4 + This is
because a signal divided by the ratio of Zf appears, and if this value is not reduced, negative
feedback due to the output voltage eo will be applied.
The reason for making the resistance smaller than the resistance R1 is to prevent the amount of
negative feedback from changing rapidly even when the connection cables Cc and Cd are
disconnected as described later.
[0057]
If the resistance R1 and the resistance R2 are on the order of several k ohms, then the impedance
of the connecting cables Cc and Cd is about 1 ohm or less, so a value of about 100 ohms to
several k ohms is selected for the resistors R3 and R4. it can.
[0058]
In this way, since the resistors R3 and R4 have sufficiently large values with respect to the
impedances of the connection cables Ca and Cb, the current for driving the speaker device SS
flows in the direction of the connection cables Ca and Cb.
[0059]
When all the connection cables Ca, Cb, Cc, and Cd are connected, the equation 7 described with
reference to FIG. 1 is established, and an ideal drive state is obtained.
10-04-2019
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[0060]
In addition, even if one or both of the connection cables Cc and Cd are disconnected, negative
feedback is applied by the resistors R3 and R4, so the effect of the present invention can not be
expected, but a speaker device is added to a normal negative feedback amplifier. Operates in the
same way as connected.
Furthermore, even when all the connection cables Ca, Cb, Cc and Cd are disconnected, the output
amplification device PA is in a no-load state with negative feedback, and does not cause the
problems as described above.
The connection uncertainty of the connection cables Ca, Cb, Cc and Cd will be described later.
[0061]
In the above description, the output amplification device using the output transformer T for the
output has been described, but the present invention can be applied to other circuit
configurations as well.
[0062]
Next, a third embodiment in which the present invention is applied to another circuit
configuration will be described.
[0063]
FIG. 3 is a connection configuration diagram of an output amplification device and a speaker
device according to a third embodiment of the present invention.
[0064]
In FIG. 3, the output amplification device PA and the speaker device SS are connected to each
other by connection cables Ca, Cb, Cc and Cd.
The output amplifier PA includes input terminals IT0 and IT1, input terminals IT2 and IT3, an
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amplifier circuit A having a differential input circuit and a balanced output circuit, a resistor R1, a
resistor R2, a resistor R3 and a resistor R4. , R5, output terminals OT0 and OT1, and negative
feedback input terminals OT2 and OT3.
[0065]
The input terminals IT0 and IT1 are connected to the input terminals of one differential input
circuit of the amplification circuit A, and the input terminals IT2 and IT3 are connected to the
input terminals of the other differential input circuit of the amplification circuit A It is done.
Further, the input terminal IT2 is connected to one end of the resistor R2, and the input terminal
IT3 is connected to one end of the resistor R6.
The other end of the resistor R2 and the other end of the resistor R6 are connected to the
ground.
[0066]
The output terminals of the balanced output circuit of the amplifier circuit A are connected to the
output terminal OT0 and the output terminal OT1, respectively.
One end of the resistor R1 is connected to the connection point between one end of the resistor
R2 and the input terminal IT2, and the other end is connected to the negative feedback input
terminal OT2.
One end of the resistor R5 is connected to the connection point between one end of the resistor
R6 and the input terminal IT3, and the other end is connected to the negative feedback input
terminal OT3.
[0067]
10-04-2019
13
The resistor R3 has one end connected to the connection point between the other end of the
resistor R1 and the negative feedback input terminal OT2, and the other end connected to the
connection point between the output terminal of the balanced output circuit of the amplifier
circuit A and the output terminal OT0. ing.
One end of the resistor R4 is connected to the connection point between the other end of the
resistor R5 and the negative feedback input terminal OT3, and the other end is connected to the
connection point between the output terminal of the balanced output circuit of the amplifier
circuit A and the output terminal OT1. ing.
[0068]
Further, the speaker device SS includes input terminals S0 and S1, negative feedback output
terminals S2 and S3, and a speaker unit SU.
The input terminals S0 and S1 are connected to the speaker unit SU, and the negative feedback
output terminals S2 and S3 are directly connected to the input terminals S0 and S1, respectively.
[0069]
The output terminal OT0 and the input terminal S0 are connected by the connecting cable Ca,
the output terminal OT1 and the input terminal S1 are connected by the connecting cable Cb,
and the negative feedback input terminal OT2 and the negative feedback output terminal S2 are
connected by the connecting cable Cc. The negative feedback input terminal OT3 and the
negative feedback output terminal S3 are connected by the connection cable Cd, and the output
amplification device PA and the speaker device SS are connected to each other.
[0070]
Hereinafter, the operation of the connection configuration shown in FIG. 3 will be described.
[0071]
Between input voltage ei1 applied between input terminal IT0 and input terminal IT1, input
voltage ei2 applied between input terminal IT2 and input terminal IT3, and output voltage eo
appearing between output terminal OT0 and output terminal OT1 Then, assuming that the
amplification degree of the amplifier circuit A is a, the following equation 12 is established.
10-04-2019
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[0073]
The resistors R3 and R4, the output terminals OT0 and OT1, the negative feedback input
terminals OT2 and OT3, the connecting cables Ca, Cb, Cc and Cd, and the speaker device SS have
been described with reference to FIG. Is the same as
[0074]
A signal for negative feedback is divided by the resistors R1 and R2 from the negative feedback
input terminal OT2, and is divided by the resistors R5 and R6 from the output negative feedback
input terminal OT3. It is applied to the input terminal (input terminal IT2 and input terminal IT3)
of the dynamic input circuit.
[0075]
Here, in the state where connection cables Cc and Cd are not connected, negative feedback is
applied to the output voltage eo appearing between the output terminal OT0 and the output
terminal OT1, assuming the following equation (13).
[0077]
【0077】また、
[0080] 【0080】とそれぞれおき、
[0082] Then, the following equation 17 is established.
[0084] Therefore, the following equation 18 is established from the equations 12, 13, 14, 15, 16,
and 17.
[0086] Therefore, if the amplification degree a is sufficiently large, the amplification degree af at
the negative feedback is expressed by the following equation 19, and the same result as the
principle of the negative feedback explained by FIG. 2 is obtained.
[0088] In practice, since the resistors R3 and R4 have the same finite values as described in FIG.
10-04-2019
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2 and the connecting cables Cc and Cd are connected, the negative feedback is given by the
output terminal OT0 and the output terminal It is not the same for the output voltage eo
appearing between OT1 but for the input voltage es between the input terminal S0 and the input
terminal S1 of the speaker device SS as in the configuration of FIG. Will be established.
[0090] Next, a fourth embodiment in which the present invention is applied to an output
amplification apparatus having a configuration in which the output is unbalanced and can not be
separated from the ground will be described.
[0091] FIG. 4 is a connection configuration diagram in which the present invention is applied to
an output amplification device having a configuration in which the output is unbalanced and can
not be separated from the ground.
[0092]
In FIG. 4, the difference from the connection configuration shown in FIG. 3 is that the output of
the amplifier circuit A is unbalanced, and one terminal of this output is grounded.
Also in this configuration, the negative feedback circuit for the input voltage es between the
input terminal S0 and the input terminal S1 of the speaker device SS is the same as the circuit of
FIG. 3, and the same purpose can be achieved.
[0093] Next, in the connection configurations shown in FIG. 2 to FIG. 4, an operation when
connection of the connection cables Ca, Cb, Cc and Cd is uncertain will be described.
[0094]
Since four connection cables of connection cables Ca, Cb, Cc and Cd can be in two states of
connected and not connected respectively, there are 16 connection states in total.
The operation and action in the connection state will be described below.
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16
In addition, since it is complicated to describe all the combinations, they are collectively
explained to some extent.
[0095]
First, in a state where all of the connection cables Ca, Cb, Cc and Cd are connected, an ideal drive
state is obtained.
Further, even when all the connection cables Ca, Cb, Cc, and Cd are not connected, the output
amplification device PA is in a no-load state where negative feedback is applied, and does not
cause any problem.
[0096]
Even when connection cables Cc and Cd are not connected while connection cables Ca and Cb are
connected, the operation is the same as when a speaker device is connected to a normal negative
feedback amplifier. Do.
However, in this case, the effects of the present invention can not be expected.
[0097]
When either or both of the connection cables Ca and Cb are not connected, either or both of the
connection cables Cc or Cd are connected, and either the resistor R3 or the resistor R4 is
connected to the speaker unit SU. When the drive current flows through either or both, the
voltage applied to the speaker unit SU is a value obtained by dividing the resistance R3, the
resistor R4 or the sum of the resistors R3 and R4 and the impedance of the speaker unit SU, and
the power applied to the speaker unit SU Will decrease significantly. Therefore, there is no
concern that the speaker unit SU emits a loud volume. At the same time, the amount of negative
feedback also decreases, and therefore, when designing the amplifier circuit A, it is necessary to
configure so that the circuit does not become unstable even in that state.
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17
[0098] A fifth embodiment will be described which secures a certain amount of negative
feedback even in such a case.
[0099] FIG. 5 is a connection configuration diagram between an output amplifying device and a
speaker device according to a fifth embodiment of the present invention which secures a fixed
amount of negative feedback. That is, in the connection configuration shown in FIG. 5, the
countermeasure circuit is incorporated into the connection configuration shown in FIG. 3 so that
a certain amount of negative feedback is always secured.
[0100] In FIG. 5, the difference of the connection configuration from FIG. 3 is that the circuit
further includes a resistor R7 and a resistor R8. The resistor R7 has one end connected to the
input terminal of the other differential input circuit of the amplifier circuit A, the input terminal
IT2, one end of the resistor R2 and one end of the resistor R1, and the other end is the amplifier
circuit A The output terminal of the balanced output circuit is connected to the connection point
between the output terminal OT0 and the other end of the resistor R3.
[0101] Furthermore, one end of the resistor R8 is connected to the connection point of the other
differential input circuit of the amplifier circuit A, the input terminal IT3, one end of the resistor
R6 and one end of the resistor R5, and the other end is amplified It is connected to the
connection point of the output terminal of the balanced output circuit of the circuit A, the output
terminal OT1 and the other end of the resistor R4.
[0102] Thus, by adding the resistors R7 and R8, negative feedback is applied by the resistors R7
and R8 regardless of the connection state of the connection cables Ca, Cb, Cc and Cd. The
resistance R7 and the resistance R8 are unnecessary if the connection cables Ca, Cb, Cc and Cd
are not detached, and the resistance R7 and the resistance R8 are unnecessary, and even if these
are inserted, the resistance R7 is a resistance as long as it is necessary for stability. The
resistance value is sufficiently larger than R1, and the resistance R8 is sufficiently larger than the
resistance R5 so that the main negative feedback is applied by the input voltage es of the speaker
device SS.
[0103] In the connection configurations shown in FIGS. 1 to 5, the speaker device SS has been
described as providing the negative feedback output terminals S2 and S3. However, regardless of
the essence of the present invention, the connecting cable Cc for negative feedback is provided. It
will be appreciated that Cd and Cd may be connected directly to the input terminals S0 and S1
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instead of to the negative feedback output terminals S2 and S3, respectively.
[0104] As described above, according to the present invention, since the input voltage of the
output amplification device and the input voltage of the speaker device have a linear relationship,
the distance between the output amplification device and the speaker device is equivalently made
zero. High fidelity music playback without expensive connection cables or bi-wiring schemes. In
addition, the effects of the present invention make a significant difference in actual trial listening,
and are extremely effective particularly in the reproduction of the bass region.
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