JPH0161000B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sound quality adjustment circuit, and more particularly to a sound quality adjustment circuit for improving the stereo effect in stereo playback equipment.

In stereo playback equipment, especially small portable tape recorders, in order to improve the stereo effect, an inverted signal of the right channel signal is added to the left channel signal, and an inverted signal of the left channel signal is added to the right channel signal. Conventionally, a sound quality adjustment circuit has been used which adds signals and outputs the respective signals. Generally, the left and right channel signals are respectively given an in-phase component signal and an uncorrelated signal, and the center position of the sound image is obtained by the in-phase component signal. However, in the conventional sound quality adjustment circuit described above, inverted signals are added at a fixed ratio, so the in-phase component is canceled out, and the component localized to the center of vocals and low-frequency rhythm instruments is reduced, resulting in a blurred sound image. . On the other hand, when considering uncorrelated components, as an extreme example, there is a signal in only one channel and no signal in the other channel,
The left and right outputs will be completely out of phase, giving you a strange feeling.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a sound quality adjustment circuit for a stereo reproduction device that can increase the sense of spaciousness of sound without changing the center component level or giving a sense of discomfort.

The sound quality adjustment circuit of the present invention detects the sum signal and difference signal of both left and right channel signals, and generates two average DC signals each representing a value obtained by individually rectifying and averaging the sum signal and the difference signal. , generates a control signal according to the difference between the two average DC signals, amplifies the difference signal component between the left and right channel signals while controlling the gain of the gain control amplifier using the control signal, and connects this amplified output with the left channel signal. and the inverted signal of this amplified output and the right channel signal are added, and each of these summed outputs is used as a left and right stereo output signal.

The present invention will be explained below using the drawings.

The figure is a block diagram of an embodiment of the present invention, in which left and right channel signals L and R each serve as one input to adders 8 and 9, respectively. On the other hand, these channel signals L and R are transmitted to subtracters 10 and 12 and adder 11.
A difference signal LR and a sum signal L+R are respectively input. The difference signal L-R from the subtracter 10 is applied to a gain control type amplifier (hereinafter referred to as VCA) 4,
It will be amplified with a gain depending on the control signal Vc. The sum and difference signal components of the adder 11 and the subtracter 12 are rectified by the detectors 1 and 2, respectively, and then input to the smoothers 6 and 7, where they are converted to DC levels, respectively. These DC outputs V ₊ and V _- are differentially amplified by a differential amplifier 3 to obtain an output Vc, which is used as a control signal for the VCA 4.

The amplified output of the VCA 4 becomes another input to the adder 8, and is added to the left channel signal L to drive the left speaker system. Further, the amplified output of the VCA 4 is inverted by a phase inverter 5 and becomes another input to the adder 9, which is added to the right channel signal R to drive the right speaker system.

In such a configuration, if the in-phase component between the left and right channels is C, and the uncorrelated components are L'' and R'', respectively, it can be expressed as L=C+L''R=C+R''. Adder 11 and subtracter 12
The sum signal L+R and the difference signal LR given to are L+R=2C+L"+R"LR=L"-R". These signals are transmitted through detectors 1 and 2, smoother 6,
7, it is converted to an average DC level, and its output D becomes D _L+R =2+″+″ D _LR =″+″. Here, L″ and R″ are uncorrelated components, so
Both L″+R″ and “−” are 0. Therefore, the output of the differential amplifier 3, Vc, is D _L+R −D _LR = ^2C , that is, a signal commensurate with the common mode component. Therefore, a detection signal corresponding to the center component level is obtained at the output Vc of the differential amplifier 3. The gain of VCA4 due to this detection signal Vc is k (k≧0)
Then, each output L' and the output of adder 8 and subtracter 9
R' is expressed as L'=L+k(L-R) R'=R+k(R-L)...(1).

Here, the sense of expansion of the sound image is that on July 15, 1978,
"Speaker System (Part 1)" published by Radio Gijutsusha
(by Takeo Yamamoto), pages 97 and 98, it can be expressed as a cross-correlation coefficient that shows how similar signals are, and the correlation coefficient for completely identical signals is 1, The correlation coefficient between completely unrelated signals is 0
It is expressed as Therefore, by creating unrelated signals, the correlation coefficient approaches 0 and a sense of expansion is obtained.

In other words, in equation (1), the outputs L′ and R′ are the original sound (1
+k) mutually uncorrelated −kR for the doubled amplified output,
-kL is added to the output, and the sense of spaciousness due to uncorrelated components can be expanded.

Furthermore, since the gain k is determined according to the in-phase component level, a greater sense of spaciousness can be obtained when the signal has many in-phase components, that is, a signal with a narrow sense of sound expansion, and conversely, k is set small for uncorrelated signals. is,
You will no longer feel any discomfort. In particular, when the level of the center-localized component of vocals or low-frequency rhythm instruments is high, the stereo effect is impaired in small portable tape recorders and television sets. Accordingly, the sense of sound spreading becomes better and the stereo feeling increases.

[Brief explanation of drawings]

The figure is a block diagram of an embodiment of the invention. Explanation of symbols of main parts, 4...VCA, 8, 9,
11...Adder, 10,12...Subtractor.

Claims (1)

[Claims] 1 means for respectively detecting a sum signal and a difference signal of the left and right channel signals; means for generating two average DC signals each representing a value obtained by rectifying and averaging the sum signal and the difference signal individually; means for generating a control signal responsive to the difference in the average DC signal;
gain control type amplification means whose gain is controlled by the control signal and amplifies the difference signal between the left and right channel signals; addition means for adding the output of the amplification means to the left channel signal; 1. A sound quality adjustment circuit comprising: adding means for adding inverted signals of outputs, and each output of the adding means is made into left and right stereo output signals.