JP2009065436A - Stereo reproducing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stereo reproducing apparatus which emphasizes a high frequency range without influencing a human voice band, makes localization of a sound image clear, and can use a filter of simple configuration. <P>SOLUTION: This stereo reproducing apparatus includes: an adder 5 which generates a difference signal between an L signal and an R signal to be input; a high-pass filter 6 connected to the output side of the adder 5; gain variable amplifiers (7, R1, R2) which amplify an output signal of the bypass filter 6; an adder 8 which adds output signals of the gain variable amplifiers to an original L signal; and an adder 9 which subtracts the output signals of the gain variable amplifiers from an original R signal. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a stereo reproduction apparatus that inputs an L signal and an R signal of two channels and outputs an L signal and an R signal in which high frequencies are emphasized.

  Most of the audio frequency distribution that can be heard by humans is concentrated in the vicinity of 300 Hz to 3.5 kHz, and it is said that it is around 1 kHz that is important for intelligibility in conversation. When performing high-frequency adjustment, it is desirable that this human voice band is not affected.

  Usually, the high frequency emphasis circuit is configured by inserting high pass filters 21 and 22 into the L signal line and the R signal line as shown in FIG. In FIG. 5, 1 is an L signal input terminal, 2 is an R signal input terminal, 3, 4, 10, and 11 are voltage followers for impedance conversion, 12 is an L signal output terminal, and 13 is an R signal output terminal. In the circuit shown in FIG. 5, the L signal and the R signal pass through the high pass filters 21 and 22, so that the high frequency components are relatively emphasized and output from the output terminals 12 and 13.

  Further, as shown in FIG. 6, the output signals of the voltage followers 3 and 4 are added by an adder 23, a high-pass component is extracted from the added signal by a high-pass filter 24, and a gain comprising an operational amplifier 7 and resistors R1 and R2 is obtained. Amplification is performed by a variable amplifier, and the signals are added to the L signal and the R signal by adders 25 and 26, respectively. As the high pass filter 24, one having a cutoff frequency of about 10 kHz as shown in FIG. 7 is used. In the circuit shown in FIG. 6, the high frequency component of the components of the L signal and the R signal is emphasized. Therefore, the reverberation sound and the reflected sound are also emphasized at the same time and added to the L signal and the R signal. The emphasis effect was realized.

  However, in the high-frequency emphasis circuit shown in FIG. 5, the high-pass filters 21 and 22 are directly inserted into the signal line, and the frequency characteristics of the original signal are directly manipulated, so depending on the attenuation characteristics of the high-pass filters 21 and 22, It also affects the human voice band, and the localization of the sound image may become unclear. In order to configure the high-pass filters 21 and 22, generally, a large capacity is required. Therefore, when the stereo reproduction apparatus is integrated into an IC, two are required for both channels. There is a problem that the number of pins increases.

  In addition, the high frequency emphasis circuit shown in FIG. 6 takes out a high frequency component from the added component of the L signal and the R signal and adds it to the original L signal and the R signal in common, so that the localization of the sound image is also unsatisfactory. There is a problem that the sound quality becomes clear and distorted.

  An object of the present invention is to provide a stereo reproduction apparatus that performs high-frequency emphasis without affecting the human voice band, makes the localization of the sound image clear, and allows the filter to have a simple configuration. .

  To achieve the above object, the present invention provides a first adder that generates a difference signal between an input L signal and an R signal, a high-pass filter connected to an output side of the first adder, A second adder that adds the output signal of the high-pass filter so that the L component is enhanced with respect to the L signal; and the output signal of the high-pass filter is enhanced with respect to the R signal. In a stereo reproduction device including a third adder for adding, the high-pass filter has a cutoff frequency of 2 kHz to 4 kHz and an attenuation characteristic of −6 dB / oct.

  According to the present invention, the high frequency component of the difference component between the L signal and the R signal is extracted and added so that the L component is enhanced in the original L signal and the R component is enhanced in the original R signal. Therefore, by setting the cut-off frequency and attenuation characteristics of the high-pass filter as described above, the localization of the sound image can be clarified without affecting the human voice band near 1 kHz, and the number of capacitors required is small. That's it.

  FIG. 1 is a block diagram showing the configuration of a stereo playback apparatus according to one embodiment of the present invention. 1 is an L signal input terminal, 2 is an R signal input terminal, 3 and 4 are voltage followers for impedance conversion, 5 is an adder that subtracts the R signal from the L signal, and 6 is a high-pass filter having the characteristics shown in FIG. 7 is an operational amplifier, R1 and R2 are variable resistors that determine the gain of the operational amplifier 7, 8 is an adder that adds the output signal S1 of the operational amplifier 7 to the original L signal, and 9 is the output of the operational amplifier 7 from the original R signal. Adders for subtracting the output signal S1, 10 and 11 are voltage followers for impedance conversion, 12 is an L signal output terminal, and 13 is an R signal output terminal.

  The adder 5 subtracts the R signal from the L signal (LR) to remove the signal component that localizes the sound image at the center and extracts the reverberation signal component on the L side. The difference signal obtained there Among the components, there are few low-frequency components, and a high-frequency “Sasi-Seso” component with a few vocals and reverberant sound are mainly used.

  This difference signal component is input to the high pass filter 6 to remove a low frequency component of 3 kHz or less. As shown in FIG. 2, the high-pass filter 6 has a gentle attenuation characteristic of −6 dB / oct at a cutoff frequency of 3 kHz, so that a signal in the vicinity of 1 kHz that is a vocal band is greatly attenuated.

  The variable gain amplifier including the operational amplifier 7 and the resistors R1 and R2 adjusts the gain of the high frequency component of the difference signal component output from the high pass filter 6. The gain-adjusted difference signal component S1 is added to the original L signal by the adder 8, so that the L component is added and emphasized in the L signal line. Since the original R signal is subtracted by the adder 9, the R component is added and emphasized in the R signal line. Therefore, if the gain in the variable gain amplifier is a predetermined value, the high frequencies of the L signal and the R signal are greatly emphasized independently. For this reason, the localization of the sound image becomes clear without greatly affecting the human voice band.

  As shown in FIG. 3, the high-pass filter 6 can be composed of one capacitor C1 and one resistor R3. In this circuit configuration, the capacitor C1 has a large capacitance value. Therefore, when the stereo reproduction apparatus of the present embodiment is made into an IC, it is externally attached, but at this time, the number of pins of the IC is only increased by one. The high-pass filter 6 can be configured using a gm amplifier having a large output impedance and a capacitor having a low capacitance value. In this case, the capacitor can be built in the IC. When it is built, there is a possibility of deteriorating S / N.

  FIG. 4 is a block diagram showing the configuration of a stereo reproduction apparatus according to another embodiment of the present invention. Here, the adder 5A subtracts the L signal from the R signal (R−L), the adder 8A subtracts the gain-adjusted difference signal component S2 from the original L signal, and the adder 9A acquires the original R signal. Is added with the difference signal component S2 whose gain has been adjusted. Since the difference signal component S2 whose gain has been adjusted is subtracted from the original L signal by the adder 8, the L component is added and emphasized in the L signal line. Further, since the adder 9 adds the original R signal, the R component is added and emphasized in the R signal line. As described above, the operation of high frequency emphasis is exactly the same as that of the stereo reproduction apparatus shown in FIG.

  In the embodiment shown in FIG. 1 and FIG. 4, the characteristics of the high-pass filter 6 are set to have a gradual attenuation characteristic of −6 dB / oct with a cutoff frequency of 3 kHz as a result of the audibility test for the subject. It has been confirmed that the desired high-frequency emphasis effect can be obtained if the cutoff frequency is in the range of 2 kHz to 4 kHz.

It is a block diagram which shows the structure of the stereo reproduction apparatus of one Example of this invention. It is a frequency characteristic figure of the high pass filter of the stereo reproduction | regeneration apparatus of FIG. FIG. 2 is a circuit diagram of a high pass filter of the stereo reproduction device of FIG. 1. It is a block diagram which shows the structure of the stereo reproduction apparatus of another Example of this invention. It is a block diagram which shows the structure of the stereo reproduction apparatus which performs the conventional high region emphasis. It is a block diagram which shows the structure of the stereo reproduction apparatus which performs the high region emphasis of another conventional example. It is a frequency characteristic figure of the high pass filter of the stereo reproduction | regeneration apparatus of FIG.

Explanation of symbols

1: L signal input terminal 2: R signal input terminal 3, 4, 10, 11: Voltage follower for impedance conversion 5, 5A, 8, 8A, 9, 9A: Adder 6: High-pass filter 7: Operational amplifier 12: L signal output terminal 13: R signal output terminal

Claims (1)

A first adder that generates a difference signal between the input L signal and the R signal, a high-pass filter connected to the output side of the first adder, and an output signal of the high-pass filter with respect to the L signal A stereo including a second adder for adding the L component so that the L component is emphasized, and a third adder for adding the output signal of the high-pass filter so that the R component is emphasized with respect to the R signal In the playback device,
A stereo reproduction apparatus characterized in that the high-pass filter has a cutoff frequency of 2 kHz to 4 kHz and an attenuation characteristic of -6 dB / oct.

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