JPH0783520B2 - Surround signal generation circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a surround signal generation circuit that generates a surround signal, and more specifically, to an arithmetic operation for generating a surround signal by an amplifier provided in a sound quality adjustment device. A surround signal generation circuit for performing

(Prior Art) In a stereo device or the like, an arithmetic circuit for performing arithmetic operations on left and right channel signals is required to generate a surround signal used for the purpose of giving a more realistic sensation to the reproduced sound. Therefore, a configuration is generally adopted in which a dedicated operational amplifier (hereinafter referred to as an OP amplifier) is provided in the output section of the sound quality adjusting circuit for both the left and right channels and the above-mentioned calculation is performed by this OP amplifier.

(Problems to be Solved by the Invention) As described above, in order to generate a surround signal, it is necessary to provide a dedicated OP amplifier for the generation. This is
Addition of OP amplifier price, increase in size of printed wiring board due to mounting, etc. causes increase in manufacturing cost and obstacles to device miniaturization. Strong demand for miniaturization and sound with severe price competition. In a product, the addition of such an OP amplifier has been a cause of weakening the competitiveness in the sale of the product.

The present invention was created to solve the above problems, and an object thereof is to generate a surround signal without adding a dedicated OP amplifier by using a sound quality adjustment device such as a conventional graphic equalizer. Another object of the present invention is to provide a surround signal generation circuit capable of doing the above.

(Means for Solving the Problem) In the surround signal generation circuit of the present invention, the sound quality adjusted signal, which is the audio input signal for which the sound quality is adjusted, is guided to the plus input, and the minus input and the output of itself are provided. In a sound quality adjustment device in which operational amplifiers configured to be connected via feedback resistors are provided in the left and right audio signal paths, the audio input signal guided to the left audio signal path is used as the left audio input signal, and the right audio signal path When the audio input signal guided to the right audio input signal is set to the right audio input signal, the right audio input signal is introduced to the negative input of the operational amplifier provided in the left audio signal path through the open / close switch and the right series resistor. The left audio input signal is guided to the negative input of the operational amplifier provided in the audio signal path through the open / close switch and the left series resistor. The values of the feedback resistor, the left series resistor and the right series resistor are set to be equal.

(Function) The right audio input signal is guided to the negative input of the operational amplifier provided in the left audio signal path through the open / close switch and the right series resistor, and is supplied to the negative input of the operational amplifier provided in the right audio signal path. Since the left audio input signal is guided through the open / close switch and the left series resistor, each signal path becomes an independent path when each open / close switch is opened, and functions as a conventional graphic equalizer. It will be.

On the other hand, the sound quality adjustment signal is guided to the plus input of the OP amplifier provided on the audio signal path of the left channel, the output of the OP amplifier itself is guided to the minus input via the feedback resistor, and the open / close switch and right switch are connected. Since the right audio input signal is guided through the series resistor, the value of the feedback resistor is r ₅ , the value of the right series resistor is r ₁ , and the levels of the left audio input signal and the right audio input signal are L respectively. , R and the output of the OP amplifier is L _OUT , L _OUT = L × (r ₅ + r ₁ ) / r ₁ −R × r ₅ / r ₁ (1) holds. Then, in the equation (1), if the values of the feedback resistance and the right series resistance are made equal, then L _OUT = 2 × L−R (2)

Similarly, the OP provided on the audio signal path of the right channel
The output (R _OUT ) of the amplifier is R _OUT = 2 × RL ... (3).

Since these signals are guided to the power amplifier for output and sent to the speaker matrix, the surround signal represented by L _OUT −R _OUT = 3 × (LR) (4) is generated, and the surround effect is produced. Show.

That is, in the surround signal generation circuit of the present invention, when the open / close switch is opened, each signal path becomes an independent path and functions as a conventional graphic equalizer, and when the open / close switch is closed, Since the signal of the other channel is guided to each minus input of the operational amplifier in the signal path through each series resistor,
It produces a surround effect. In other words, the surround signal generating circuit of the present invention utilizes a conventional sound quality adjusting device such as a graphic equalizer to obtain a surround effect without adding a dedicated operational amplifier to the device.

(Embodiment) FIG. 1 is a circuit diagram showing electrical connection of an embodiment of the present invention.

In the figure, the output of the OP amplifier 1 in which the left audio input signal S _L is guided to the plus input is guided to the minus input of the OP amplifier 1 itself, and also through the resistor R ₃ , the sound quality adjustment signal S It becomes _L1 and is connected to the plus input 21 of the OP amplifier 2. Then, between the positive input 21 and the negative input 22 of the OP amplifier 2, three variable resistors VR ₁ , VR ₃ and VR are provided.
₅ are connected in parallel, and the output of the OP amplifier 2 is connected to the minus input 22 via the feedback resistor R ₅ .

The sliding terminal T ₁ of the variable resistor VR ₁ is led to one terminal of the capacitor C ₃ and the resistor R ₇ via the capacitor C ₁ , and the other terminal of the capacitor C ₃ is connected to the positive input of the OP amplifier 5. ,
The other terminal of the resistor R ₇ is connected to the negative input of the OP amplifier 5. The plus input is grounded via the resistor R ₉ , and the minus input is connected to the output of the OP amplifier 5 itself.

Also, through the capacitor C ₅ , the sliding terminal T of the variable resistor VR ₃ is
Via the block connected to ₃ and the capacitor C ₉ ,
The block connected to the sliding terminal T ₅ of the variable resistor VR ₅ is
Since it has the same structure as the block composed of the capacitor C ₃ , the resistors R ₇ and R ₉ , and the OP amplifier 5, its description is omitted.

The five OP amplifiers 3,6,8,1 shown in the lower half of Fig. 1
The configuration of the block consisting of 0, 4 and the three variable resistors VR ₂ , VR ₄ , VR ₆ and the resistors and capacitors is the same as that of the block described above and illustrated in the upper half of FIG. 1. Since the configuration is omitted, the description of the configuration will be omitted, and in the following, different portions of the configuration of the blocks shown in the upper half and the lower half of FIG. 1 will be described.

The output of the OP amplifier 1 is led to one terminal of the left series resistor R ₂ via the open / close switch SW _2, and the other terminal of the left series resistor R ₂ is connected to the minus input 42 of the OP amplifier 4. There is. The output of the OP amplifier 3 is guided to the minus input 22 of the OP amplifier 2 via the open / close switch SW ₁ and the right series resistor R ₁ .

With regard to the embodiment of the present invention having the above-described configuration, the operation when the open / close switches SW ₁ and SW ₂ are opened will be described first.

Since the OP amplifier 1 operates as a voltage follower for conversion to low impedance, its output is
A signal having the same waveform as the left audio input signal S _L led to the positive input appears and is given to one end of the resistor R ₃ .

Also, the sliding terminals T ₁ , T ₃ , T of the _three variable resistors VR ₁ , VR ₃ , VR _5
In the block connected to ₅ , the impedance when viewed from the sliding terminal side drops near the frequency centered on the frequency determined according to the setting of the capacitor and resistance provided in each block. It has a configuration (this operation is known, and therefore the operation description is omitted).

Therefore, for example, in the variable resistor VR ₁ , when the set frequency of the block including the OP amplifier 5 is f, the sliding terminal T ₁ of the variable resistor VR ₁ is grounded with low impedance in the vicinity of the frequency f. Means that.

Now, assuming that the position of the sliding terminal T ₁ is close to the negative input side of the OP amplifier 2, the negative input 22 of the OP amplifier 2 is grounded with a low impedance, so that the impedance of the low impedance and the feedback resistor R ₅ is The OP amplifier 2 operates according to the amplification factor determined by the ratio. That is, the amplification factor of the OP amplifier 2 increases near the frequency f. Therefore, in the output of the OP amplifier 2, an audio signal having an increased level appears near the frequency f.

On the other hand, when the sliding terminal T ₁ is brought close to the sound quality adjustment signal S _L1 side, the impedance for grounding the negative input 22 becomes high, the ratio of the feedback resistor R _{5 to} the ground impedance becomes small, and the amplification of the OP amplifier 2 is increased. As the rate decreases, the output of the OP amplifier 1 is divided by the resistor R ₃ and the ground impedance of the variable resistor VR ₁ , and the divided signal is guided to the plus input 21 of the OP amplifier 2. At the output of the OP amplifier 2, an audio signal whose level is lowered appears near the frequency f.

These operations are also the same in the variable resistors VR ₃ and VR ₅ , and only the center frequencies subject to level attenuation or increase are different.

The above operation is the same in the path of the right audio input signal S _R. In other words, the present embodiment is configured to operate as a three-element graphic equalizer when the open / close switches SW ₁ and SW ₂ are open.

Next, the operation when the open / close switches SW ₁ and SW ₂ are closed will be described.

At this time, in addition to the operation as the three-element graphic equalizer described above, the negative inputs 22 and 42 of the respective OP amplifiers 2 and 4 are connected via the right series resistor R ₁ and the left series resistor R ₂ to Since the signal of another channel is being guided, the output of the OP amplifier 1 is L, the output of the OP amplifier 3 is R, the value of the right series resistor R ₁ is r ₁ , the value of the left series resistor R ₂ is r ₂ , and the feedback resistance
When the values of R ₅ and R ₆ are represented by r ₅ and r ₆ , respectively, the equivalent circuit of the OP amplifier 2 is as shown in FIG. 2 (however, r ₁₀ and r ₁₁
Indicates the effect of connecting _three variable resistors VR ₁ , VR ₃ and VR ₅ ), and the output of OP amplifier 2 (indicated by L _OUT )
Is L _OUT ≈L × (r ₅ + r ₁ ) / r ₁ −R × r ₅ / r ₁ (5) (not completely equal due to the influence of r ₁₀ and r ₁₁ ).

At this time, since the value of r _{1 and} the value of r ₅ are set to be equal to each other, when the influence of r ₁₀ and r ₁₁ is ignored, L _OUT = 2 × L−R (6) Similarly OP output of the amplifier 4 (indicated by R _OUT) is R _OUT = shown as _{R × (r 6 + r 2} ) / r 2 -L × r 6 / r 2 ... (7) R OUT = 2 × R- L ... (8)

These outputs are led to the power amplifiers for output provided corresponding to each of them and sent to the speaker matrix, so that L _OUT −R _OUT = 3 × (LR) (9) A surround signal is generated, producing a surround effect.

In addition, in the above-described embodiment, the case where the present invention is applied to the graphic equalizer of three elements has been described, but it is also possible to apply the present invention to a graphic equalizer of any number of elements, for example, five elements.

Also, the case where it was applied to a graphic equalizer as a sound quality adjustment device was explained, but the level of low-frequency and high-frequency signals is attenuated and increased, and the sound quality adjusted signal is guided to the positive input and The same can be applied to a sound quality adjusting device having an OP amplifier whose input is connected to its own output via a feedback resistor.

(Effect of the Invention) In the surround signal generation circuit of the present invention, the sound quality adjustment signal is guided to the positive input, and the operational amplifier in which the negative input and the output are connected via the feedback resistor is provided in each of the left and right audio signal paths. Applied to the sound quality adjustment device with the
Lead the right audio input signal to the negative input of the operational amplifier provided on the left audio signal path through the open / close switch and the right series resistor, and connect the open / close switch to the negative input of the operational amplifier provided on the right audio signal path. The left audio input signal is guided through the left series resistor. Therefore, when each open / close switch is opened, each signal path becomes an independent path and functions as a conventional graphic equalizer. When each open / close switch is closed, each signal path operates as an operational amplifier. Since the signal of the other channel is guided to the negative input through each series resistor, the surround effect can be generated together. In other words, the surround signal generation circuit of the present invention generates the surround signal by guiding the audio input signal of the other channel to the negative input of each operational amplifier through the series resistance having the resistance value equal to the value of the feedback resistance. Since it is configured to perform calculations for, using a sound quality adjustment device such as a conventional graphic equalizer, without adding an operational amplifier dedicated to the calculation,
A surround signal can be generated.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing the electrical connection of one embodiment of the present invention,
FIG. 2 is an equivalent circuit diagram showing the operation of the operational amplifier. 2,4 …… Operational amplifier 21,41 …… Plus input 22,42 …… Minus input S _L …… Left audio input signal S _R …… Right audio input signal S _L1 , S _R1 …… Sound quality adjustment signal R ₁ …… Right series resistance R ₂ …… Left series resistance R ₅ , R ₆ …… Feedback resistance

Claims (1)

[Claims] 1. An operational amplifier having a configuration in which a tone-quality adjusted signal, which is an audio input signal whose sound quality is adjusted, is introduced to a positive input, and a negative input and an output of itself are connected via a feedback resistor. In the sound quality adjusting device provided in each of the left and right audio signal paths, the audio input signal guided to the left audio signal path is the left audio input signal, and the audio input signal guided to the right audio signal path is the right audio input signal. At this time, the right audio input signal is guided to the negative input of the operational amplifier provided in the left audio signal path through the open / close switch and the right series resistor, and the negative input of the operational amplifier provided in the right audio signal path. , The left audio input signal is guided through the open / close switch and the left series resistance, and the value of the feedback resistance, the left series resistance, and the right series resistance. Surround signal generation circuit, characterized in that it is set equal.