JP2575455Y2 - Audio signal cancellation circuit - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio signal canceling circuit for generating a karaoke signal from a normal music source of an audio device without using a karaoke source. The present invention relates to a signal cancellation circuit.

[0002]

2. Description of the Related Art In a conventional audio signal canceling circuit, as shown in FIG. 3, a left channel signal (L signal) through a buffer amplifier is input to an inverting input terminal of an amplifier 11, and a right channel signal through a buffer amplifier is input. The signal (R signal) is input to the non-inverting input terminal of the amplifier 11, and a {-(LR)} signal is generated in the amplifier 11, where L = R (monaural) among the left channel and right channel input signals. Are subtracted and do not appear at the output of the amplifier 11. Here, the capacitors C ₁₁ and C ₁₂ are capacitors for obtaining a predetermined frequency characteristic in a high frequency range.

[0003] The L signal and the R signal that have passed through the buffer amplifier are also input to an amplifier 12 configured in the same manner as the amplifier 11 to generate a {-(RL)} signal. The L signal and the R signal passed through the buffer amplifier are combined at the resistors R ₁₁ and R ₁₂ , and the combined output is a low-pass filter 1 of 12 dB / Oct.
3 and the output of the low-pass filter 13 to the amplifier 14
Of the amplifier 11 supplied to the non-inverting input terminal of the amplifier 14, and the output {-(LR)} signal of the amplifier 11 is output. Similarly, in the amplifier 15, the output from the low-pass filter 13 and the {-(RL)} signal are added and output.

The reason why the outputs of the low-pass filter 13 are added to the {-(RL)} signal and the {-(LR)} signal by the amplifiers 14 and 15 is that the amplifier 11
Although the L = R component is canceled in the output signals of Nos. 12 and 12, the bass signal in the actual music signal has many components close to monaural.

[0005]

However, according to the above-mentioned conventional audio signal canceling circuit, there is a problem that an adder circuit is required to compensate for the lack of bass sound, and the circuit configuration becomes complicated. In addition, there is a problem that it becomes expensive.

SUMMARY OF THE INVENTION An object of the present invention is to provide an audio signal canceling circuit having a simplified circuit configuration without causing insufficient bass.

[0007]

SUMMARY OF THE INVENTION An audio signal canceling circuit according to the present invention is provided with a low-pass filter for inputting left and right channel signals and attenuating a high band including an audio signal band, and a left channel signal and an output from the low-pass filter. A first amplifier that amplifies the difference between the sum signal obtained by combining the signal and the right channel signal, and a second amplifier that amplifies the difference between the sum signal obtained by combining the right channel signal and the output signal from the low-pass filter and the left channel signal. And two amplifiers.

[0008]

According to the audio signal canceling circuit of the present invention, a signal in a low-frequency band lower than the audio signal band is output from the low-pass filter, and the first amplifier outputs the right-channel signal from the sum signal of the low-frequency band signal and the left channel signal. A signal obtained by subtracting the right channel signal from the sum signal of the bass band signal and the left channel signal is output from the second amplifier, and a monaural signal is output from the first and second amplifiers. Therefore, only the audio signal band is cut off, and a signal with an enhanced bass band is output, so that the bass sound lacking in the music signal does not run short, and the addition circuit is not separately required, and the reproduction is performed. Sometimes a karaoke signal is obtained in which only the voice located at the center is cut, and the voice with a wide spread such as a back chorus is not cut.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments. FIG.
FIG. 2 is a block diagram showing a configuration of an embodiment of the present invention.

The L signal through the buffer amplifier 1 is connected to a resistor R
_{1 to} the non-inverting input terminal of the amplifier 4, and the R signal passed through the buffer amplifier 2 is supplied to the inverting input terminal of the amplifier 4 through an input circuit 6 including resistors R ₂ , R ₃ and a capacitor C ₁ , LR) signal. Similarly, the R signal through the buffer amplifier 2 is supplied to the non-inverting input terminal of the amplifier 5 through the resistor R _5, the L signal through a buffer amplifier 1 resistors R _6, R _7, a capacitor C ₂ input circuit 7 to the inverting input terminal of the amplifier 5
Generate an (RL) signal.

The L signal passed through the buffer amplifier 1 and the R signal passed through the buffer amplifier 2 are combined by resistors R ₁₁ and R ₁₂ , the combined output has a frequency characteristic of 18 dB / Oct, and the cutoff frequency is human. Is supplied to the low-pass filter 3 which is set so as to be sharply attenuated, and the low-pass filter 3 outputs a low-frequency component. The output of the low-pass filter 3 is a resistor R ₉
Through supplied to the non-inverting input terminal of the amplifier 4 as well as added to the L signal, the amplifier 5 through the resistor R ₁₀ is supplied to the non-inverting input terminal adds the R signal. Amplifiers 4 and 5
Are left channel output and right channel output, respectively.

In the audio signal canceling circuit of the present embodiment configured as described above, the amplifiers 4 and 5 are formed to have a high-pass characteristic of 6 dB / Oct in a high-frequency range due to the presence of the capacitors C ₁ and C ₂ as shown in FIG. I have. The input L signal is input to the non-inverting input terminal of the amplifier 4 through the buffer amplifier 1, and the input R signal is input to the inverting input terminal of the amplifier 4 through the buffer amplifier 2, and is output from the amplifier 4 to (LR). A signal is output.
Further, in the amplifier 4, components of L = R (monaural) among input signals of the left channel and the right channel are canceled and output. Further, the low frequency band is not attenuated based on the frequency characteristics shown in FIG. 2, but the band near 1 KHz is attenuated, and the high frequency band exceeding 1 KHz is sequentially enhanced and output.

Similarly, the input R signal is input to the non-inverting input terminal of the amplifier 5 through the buffer amplifier 2, and the input L signal is input to the inverting input terminal of the amplifier 5 through the buffer amplifier 1. Outputs an (RL) signal. Further, in the amplifier 5, L = R (monaural) among the input signals of the left channel and the right channel.
Are canceled and output. Also, the low frequency band is not attenuated based on the frequency characteristics shown in FIG. 2, but the band near 1 KHz is attenuated, and the high frequency band exceeding 1 KHz is sequentially enhanced and output.

On the other hand, the L signal and the R signal passed through the buffer amplifiers 1 and 2 are combined by resistors R ₁₁ and R ₁₂ ,
This synthesized signal is supplied to the low-pass filter 3 and passes through the low band, and is cut off and outputted in the high band including the audio signal band. The output of the low-pass filter 3 is the resistors R ₉ and R
_The signals are respectively applied to the non-inverting input terminals of the amplifiers 4 and 5 via ₁₀ and respectively added to the L signal and to the R signal.

Here, if the buffer amplifiers 1 and 2
Suppose that a monaural signal of L = R is input to the input terminal. If the frequency is considered a range of the pass band of the low-pass filter 3 low, the resistance value of the resistance values of the resistors R ₁ and R ₉ is equal R ₁ =
If it is set to R ₉ and the output of the buffer amplifier 1 and the output of the low-pass filter 3 are set to be equal, the output e _{0 of the} amplifier 4 becomes e ₀ = １ ／ · (e _L + e the _{LPF) · (R 2 + R} 3 + R 4) / (R 2 + R 3) -e R · R 4 / (R 2 + R 3).

In the above, e _L and e _R are input signals of the left and right channels, and e _LPF is an output signal of the low-pass filter 3 (frequency characteristics due to the capacitor C ₁ are ignored) R ₂ , R ₃ , R ₄ indicates the resistance values of the resistors R ₂ , R ₃ and R ₄ , respectively.

If R ₂ + R ₃ = R ₄ and R ₁ = R ₉ , e _L = e _LPF , e _L = e _R , and e ₀ = e _L.

Considering the cutoff band of the low-pass filter 3, e _LPF = 0 and the output e _{0 of the} amplifier 4 is e ₀ = e _L · R ₁ / (R ₁ + R ₉ ) ・ (R ₂ + R ₃ + R ₄₎ / become _{(R 2 + R 3) -e} R · R 4 / (R 2 + R 3).

If R ₂ + R ₃ = R ₄ and R ₁ = R ₉ as described above, then e ₀ = e _L -e _R and e _L = e _R , so that e ₀ = 0 Becomes

That is, when a monaural signal is input, the output of the amplifier 4 changes similarly to the output of the low-pass filter 3 under the above conditions. The same applies to the amplifier 5.

Therefore, only the audio signal band is cut off for a monaural signal, and if the L signal and the R signal are different, the difference is output. Further, a low-frequency signal not including the audio signal band is low-passed. The signal is output from the filter 3, added to the L and R signals, and output. As a result, in the actual reproduced sound, only the sound located at the center is cut, and a wide sound such as a back chorus is reproduced without being cut. Furthermore, the lack of bass in an actual music signal is compensated.

In the above embodiment, the low-pass filter 3 has a monaural configuration.
It may be a stereo configuration.

[0023]

As described above, according to the present invention, a low-pass filter that receives left and right channel signals and attenuates a high band including an audio signal band, a left channel signal and an output signal from the low-pass filter are used. A first amplifier for amplifying a difference between the combined sum signal and the right channel signal, and a second amplifier for amplifying a difference between the sum signal combining the right channel signal and the output signal from the low-pass filter and the left channel signal Therefore, only the audio signal band for the monaural signal is cut off from the first and second amplifiers,
And a signal in which the bass band has been enhanced will be output, and the bass that is lacking in the music signal will not be lacking, no additional circuit is required separately, only the sound located at the center at the time of reproduction is cut, There is an effect that a karaoke signal can be obtained in which a wide voice such as a back chorus is not cut.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a frequency characteristic diagram of the amplifier according to the embodiment of the present invention;

FIG. 3 is a block diagram showing a configuration of a conventional example.

[Explanation of symbols]

 1 and 2 buffer amplifier 3 low-pass filter 4 and 5 amplifier

Claims (1)

(57) [Scope of request for utility model registration] 1. A low-pass filter to which left and right channel signals are input and attenuated in a high band including an audio signal band;
A first amplifier for amplifying a difference between the sum signal obtained by combining the left channel signal and the output signal from the low-pass filter and the right channel signal; a sum signal obtained by combining the right channel signal and the output signal from the low-pass filter; An audio signal canceling circuit, comprising: a second amplifier for amplifying a difference from a channel signal.