JP2009177559A - Vocal cut circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vocal cut circuit with a small circuit scale. <P>SOLUTION: An L channel signal and an R channel signal are respectively input to input terminals 21, 22. The L channel signal input to the input terminal 21 is input to an adder 24 as it is, and the R channel signal input to the input terminal 22, after passing an all pass filter 23, is input to the adder 24. The all pass filter 23 makes a signal of the all frequency range of the R channel signal pass and changes only the phase of the signal. Since the phases of vocal components included in the L channel signal and the R channel signal are shifted, a vocal component of an added output from the adder 24 is attenuated. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a vocal cut circuit that outputs a signal obtained by deleting the vocal component from a stereo music source including the vocal component.

  Conventionally, in an audio system such as a mini component, a stereo music source reproduced from a CD (compact disc) includes a stereo component (accompaniment portion) and a vocal component (human voice portion). With respect to the stereo component, a phase difference between the L channel signal and the R channel signal is shifted, so that a sense of stereo and a sense of sound spread can be obtained. As for the vocal component, the L channel signal and the R channel signal have substantially the same phase and are almost the same signal, so that it can be felt that sound can be heard from the center position between the speakers. In recent years, an audio system having a function of cutting a vocal component from a stereo music source has been developed. Such an audio system can be used for singing such as karaoke.

  In order to cut a vocal component from a stereo music source, as shown in FIG. 6, since the vocal components of the L channel signal and the R channel signal are substantially the same signal, the difference between the L channel signal and the R channel signal is determined. If it is taken, the vocal component can be deleted.

  However, as shown in FIG. 7, the phase shift between the stereo components of the L channel signal and the R channel signal is about 0 ° in a low frequency band (hereinafter referred to as a low band) of about 100 KHz or less. A phase shift occurs in the above frequency band (hereinafter referred to as a middle-high range). The mid-high range is about 100 KHz to about 1 KHz, and this band is a voice band. Further, 20 KHz to 20 KHz is an audible band in which a human can hear a voice.

  For this reason, if the difference between the L channel signal and the R channel signal is simply taken, there is a disadvantage that a low-frequency signal component, for example, an accompaniment drum sound is also deleted at the same time.

  Therefore, a vocal cut circuit is known in which a low-pass signal component is left using a low-pass filter (low-pass filter). FIG. 8 is a diagram showing the configuration of such a vocal cut circuit. The L channel signal and the R channel signal input from the input terminals 51 and 52 are added by the adder 53 to become an (L + R) signal, and then pass through the low-pass filter 54 so that only the low-frequency signal component is present. Extracted to become a (L ′ + R ′) signal. This (L ′ + R ′) signal is input to the (+) input terminal of the subtractor. Further, the L channel signal and the R channel signal input from the input terminals 51 and 52 are input to the (+) input terminal and the (−) input terminal of the subtractor 55, respectively.

  As a result, the subtractor 55 outputs a signal (LR−L ′ + R ′). Of the subtractor output, the (LR) signal component is a signal component obtained by cutting out the in-phase component in the entire region. Therefore, the (LR−L ′ + R ′) signal is a signal in which the in-phase component in the mid-high range is attenuated, the vocal component is cut, and the low-frequency signal component can remain.

Note that this type of vocal cut circuit is described in Patent Document 1.
JP-A-7-236197

  However, the vocal cut circuit described above requires three amplifiers: an adder 53, a low-pass filter 54, and a subtractor 55. For this reason, there exists a problem that a circuit scale becomes large. In addition, since the low-pass filter 54 is used, there is a problem that low-frequency sounds are also attenuated.

  Therefore, the present invention is a vocal cut circuit that outputs a signal obtained by deleting the vocal component from a stereo music source including a vocal component, and passes a signal in the entire frequency range of the R channel signal of the stereo music source, An all-pass filter that changes only the phase; and an addition circuit that adds the R-channel signal that has passed through the all-pass filter and the L-channel signal of the stereo music source; and a signal obtained by removing the vocal component from the addition circuit Is output.

  Since the vocal cut circuit of the present invention can be formed by only two amplifiers, ie, an all-pass filter and an adder circuit, the circuit scale can be reduced and the low-frequency sound is not attenuated. Also, by providing two vocal cut circuits of the present invention, a configuration corresponding to stereo output can be easily realized.

  Hereinafter, embodiments of the present invention will be described. First, the configuration of an audio system including the vocal cut circuit of the present invention will be described with reference to FIG. A stereo music source reproduced from the CD 1 is divided into an L channel signal and an R channel signal and input to the vocal cut circuit 2. The L channel signal and the R channel signal include a stereo component and a vocal component, respectively, and the phase of the stereo signal component is shifted between the L channel signal and the R channel signal in a middle or higher band. Regarding the vocal component, the L channel signal and the R channel signal have substantially the same phase and are substantially the same signal. The audio signal from which the vocal component has been cut by the vocal cut circuit 2 is subjected to volume adjustment by the electronic volume 3, further amplified by the power amplifier 4, and then input to the speaker 5.

  Next, the configuration of the vocal cut circuit 2 will be described with reference to FIG. The vocal cut circuit 2 has two configurations shown in FIGS. 2A and 2B. The same effect can be obtained from these configurations. First, the structure in FIG. 2A will be described. That is, the L channel signal and the R channel signal are input to the input terminals 21 and 22, respectively. The L channel signal input to the input terminal 21 is input to the adder 24 as it is, and the R channel signal input to the input terminal 22 is input to the adder 24 after passing through the all-pass filter 23. The all-pass filter 23 passes signals in the entire frequency range of the R channel signal and changes only the phase thereof. As a result, the phase of the vocal component contained in the L channel signal and the R channel signal is shifted, and the vocal component of the addition output of the adder 24 is attenuated.

  As shown in FIG. 3, the all-pass filter 23 preferably changes the phase of the R channel signal in the frequency band of the vocal component, that is, in the voice band of about 100 KHz to about 1 KHz. Further, the amount of change in phase is preferably about 90 °. Thereby, only the vocal component is attenuated, and the attenuation of the stereo component is suppressed. In addition, since there is no signal phase change in a low frequency range of about 100 KHz or lower, the low frequency sound is not attenuated.

  In the vocal cut circuit 2 described above, the all-pass filter 23 is provided on the R channel signal side. However, as shown in FIG. 2B, the same effect can be obtained even if the all-pass filter 23 is provided on the L channel signal side. Obtainable.

  Next, a specific circuit configuration of the vocal cut circuit 2 will be described with reference to FIG. FIG. 4 shows a circuit configuration of the all-pass filter 23 and the adder 24 in the vocal cut circuit 2. The all-pass filter 23 includes the first operational amplifier 23a, resistors R1, R2, R3, and R4, and a capacitor C1, and the resistors R1, R2, R3, and R4 all have the same resistance value. (R1 = R2 = R3 = R4) The phase of the R channel signal passing through the all-pass filter 23 is determined by the value of the capacitor C1 and the value of the resistor R4. The adder 24 can be formed by the second operational amplifier 24a and resistors R5, R6, R7, and R8. Then, an output signal in which the vocal component is attenuated is obtained from the adder 24.

  FIG. 5 is a diagram showing the frequency dependence of the output signal in the vocal cut circuit 2, and the gain of the output signal is greatly attenuated in the voice band of about 100 KHz to about 1 KHz, while it is low around 100 KHz. In the region, the gain of the output signal is not attenuated. However, it is assumed that the level of the input signal (R channel signal and L channel signal) is 0 dB, and the all-pass filter 23 causes a 90 ° phase change at 1 KHz.

  According to the above vocal cut circuit 2, since it can be formed by only two amplifiers, the all-pass filter 23 and the adder 24, the circuit scale can be reduced, and the low-frequency sound is not attenuated. Also, by providing two vocal cut circuits 2, a configuration corresponding to stereo output can be easily realized.

It is a figure which shows the structure of the audio system using the vocal cut circuit by embodiment of this invention. It is a figure which shows the structure of the vocal cut circuit by embodiment of this invention. It is a figure which shows the phase characteristic of an all pass filter. It is a figure which shows the specific circuit structure of the vocal cut circuit by embodiment of this invention. It is a figure which shows the frequency characteristic of the gain of an all pass filter. FIG. 4 is a waveform diagram of vocal components of an L channel signal and an R channel signal. It is a figure which shows the phase of the stereo component of a L channel signal and a R channel signal. It is a figure which shows the structure of the vocal cut circuit of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 CD 2 Vocal cut circuit 3 Electronic volume 4 Power amplifier 5 Speakers 21 and 22 Input terminal 23 All-pass filter 24 Adder 23a 1st operational amplifier 24a 2nd operational amplifier 51 and 52 Input terminal 53 Adder 54 Low-pass filter 55 Subtractor

Claims (4)

A vocal cut circuit for outputting a signal obtained by deleting the vocal component from a stereo music source including the vocal component,
An all-pass filter that passes signals in the entire frequency range of the R channel signal of the stereo music source and changes only the phase thereof;
An adder circuit that adds the R channel signal that has passed through the all-pass filter and the L channel signal of the stereo music source, and outputs a signal from which the vocal component has been removed from the adder circuit Cut circuit. The vocal cut circuit according to claim 1, wherein the all-pass filter changes the phase of the R channel signal in a frequency band of a vocal component. A vocal cut circuit for outputting a signal obtained by deleting the vocal component from a stereo music source including the vocal component,
An all-pass filter that passes signals in the entire frequency range of the L channel signal of the stereo music source and changes only the phase thereof;
An adder circuit that adds the L channel signal that has passed through the all-pass filter and the R channel signal of the stereo music source, and outputs a signal from which the vocal component has been removed from the adder circuit Cut circuit. 4. The vocal cut circuit according to claim 3, wherein the all-pass filter changes the phase of the L channel signal in a frequency band of a vocal component.

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