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JPH0638396

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DESCRIPTION JPH0638396
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
headphone circuit in which the separation of the headphone circuit is improved in a stereo
amplifier having a headphone jack.
[0002]
2. Description of the Related Art In a conventional stereo amplifier headphone circuit, as shown
in FIG. 2, for example, the left and right hot side terminals 1L and 1R of a headphone jack 1 are
respectively connected to a stereo amplifier (2) via a voltage drop resistor R1. And the common
ground-side conductor terminal 1E of the headphone jack 1 is connected to the ground circuit 2E
of the stereo amplifier 2.
[0003]
In the conventional headphone circuit having such a structure, since the ground side terminal 1E
of the headphone jack 1 is common to the left and right, as shown in FIG. There is a problem to
be solved that the wiring impedance z between the ground 1E and the ground 2E of the amplifier
2 exists as a common impedance and the separation as stereo is degraded.
[0004]
That is, the voltages flowing to the left and right hot side terminals 1L and 1R of the headphone
jack 1 are respectively VL 'and VR', and currents flowing to the left and right transducers DL and
DR of the headphone 4 (impedance is respectively ZL and ZR). Assuming that IL and IR
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respectively, the current Iz flowing in the common wiring impedance z is Iz = IL + IR, and the
voltage of the ground side terminal 1E of the headphone jack 1 to the ground side terminal 2E of
the amplifier 2 ie, the wiring impedance z The voltage Vz at both ends is Vz = z (IL + IR).
[0005]
Therefore, if the true voltages applied to the transducers DL and DR of the headphones are VL
and VR, then VL = VL'-Vz and VR = VR'-Vz, and Vz in the above equation is the sum signal
component of the left and right Since the left and right channels are mixed with channel signal
components on the opposite side, separation degradation between the channels can not be
avoided.
[0006]
Therefore, the present invention solves the drawbacks of the prior art, detects the voltage Vz of
the left and right sum signal components caused by the common wiring wiring impedance z, and
feeds it back to the headphone circuit. It is an object of the present invention to provide a
headphone circuit with perfect separation, which does not appear in the input signal of the
headphone whose effect of z is a load.
[0007]
The headphone output circuit according to the present invention for achieving the above object
will be described with reference to FIG. 1 showing an embodiment. The hot side terminals 1L and
1R are respectively connected to the left and right output terminals 2L and 2R of the stereo
amplifier 2 via the voltage drop resistance R1, and the common left side conductor 1E of the
headphone jack 1 is the earth circuit of the stereo amplifier 2 2E and detects the voltage Vz
between the common left side conductor 1E of the headphone jack 1 and the ground circuit 2E
of the stereo amplifier 2 to obtain a gain of 1 and a left hot side terminal 1L of the headphone
jack 1 , And 1R are connected, and the headphone output circuit is characterized in that the
feedback circuit 3 includes the operational amplifier 31, the resistors for gain control R3 and R4,
and the front side. It consists of two resistors R2 respectively connected to the left and right hot
side terminals 1L and 1R of the headphone jack 1, and it is provided between the resistors R3
and R4 for gain control, the resistor R2 and the voltage drop resistor R1 (R2 / R1 2. The
headphone output circuit according to claim 1, wherein the relationship is given by: R4 / R3.
[0008]
In the headphone circuit having such a configuration, the left and right ends of the wiring
impedance z inherent between the left and right common ground terminals 1E of the headphone
jack 1 and the ground circuit 2E of the stereo amplifier 2 are provided. Even if the voltage Vz
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consisting of signal components is generated, the voltage Vz is detected and is fed back to the hot
side terminals 1L and 1R of the headphone jack 1 so as to cancel the voltage Vz with a gain of 1.
It is possible that the true voltages VL and VR applied to the devices DL and DR do not include
the voltage Vz.
[0009]
In FIG. 1, ZL and ZR are the left and right impedances of the headphone 4, z is the wiring
impedance on the ground side of the headphone circuit, VLo and VRo are the output voltages of
the left and right amplifiers 2, and VL 'and VR' are the headphone jacks 1. On the left and right
sides, Vz is a voltage generated at both ends of the wiring impedance z, Vc is a compensation
voltage, and VL and VR are true voltages applied to the left and right transducers DL and DR of
the headphone 4 The relationship is given by VL = VL'-Vz and VR = VR'-Vz.
[0010]
The relationship of the equation 1 is established between the current and the voltage of each part
of the wiring diagram shown in FIG.
[0011]
From the relationship of Equation 1, currents IL and IR flowing through the left and right
transducers DL and DR (with impedances ZL and ZR, respectively) of the headphone 4 are
represented by the currents I1 and I2 from the amplifier 2 and from the feedback circuit 3. If it
calculates | requires from compensation current I3, I4, it will become like Numerical formula 2.
[0012]
When the currents IL and IR in the equation 2 and the currents IL and IR in the equation 1 are
related, the equation 3 is obtained, and the equation 3 is obtained. If the above R1, R2, R3 and R4
are set as Equation 4, the true voltages VL and VR applied to the left and right transducers DL
and DR of the headphone 4 can be expressed as Equation 5. The influence of the wiring
impedance z is eliminated, so that there is no crosstalk from other channels, and good separation
can be obtained.
[0013]
【0013】
[0014]
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【0014】
[0015]
Further, since the voltage drop resistor R1 is present, there is no influence on the speaker output.
[0016]
DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, the embodiment of the
present invention will be described in detail. A headphone jack 1 has left and right hot side
terminals 1L and 1R respectively via a voltage drop resistance R1. The ground conductor 1E
common to the left and right output terminals 2L and 2R and common to the left and right of the
headphone jack 1 is connected to the ground circuit 2E of the stereo amplifier 2.
[0017]
3 detects the voltage Vz between the left and right common grounding conductor 1E of the
headphone jack 1 and the grounding circuit 2E of the stereo amplifier 2 to obtain the gain 1 and
the left and right hot terminals 1L and 1R of the headphone jack 1; A feedback circuit for
returning to the circuit, which comprises an operational amplifier 31, gain control resistors R3
and R4, and two resistors R2 connected to the left and right hot terminals 1L and 1R of the
headphone jack 1, respectively.
[0018]
The resistances of the gain control resistors R3 and R4, the resistor R2 and the voltage drop
resistor R1 are as follows:
(R2 / R1) = (R4 / R3), that is, expressed in another form, (2).
(R1 + R2) / R1 = (R3 + R4) / R3, or (3).
Set to have a relationship of R3 = kR1, R4 = kR2
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[0019]
Although the headphone circuit according to the present invention has been described in detail
based on the embodiment considered to be representative, the embodiment of the headphone
circuit according to the present invention is not limited to the structure of the above
embodiment, The invention can be appropriately modified and implemented as long as it has the
configuration requirements described in the above-described utility model registration request,
exhibits the effect according to the present invention, and has the effects described below.
[0020]
[Effects] The headphone circuit according to the present invention has the following effects.
That is, in the headphone jack, even in the conventional headphone jack in which the left and
right ground conductors are common, it is possible to eliminate left and right crosstalk due to the
wiring impedance accompanying the common ground circuit.
Therefore, to get complete separation
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