JPS6230325Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tone control circuit.
A tone control circuit conventionally used is, for example, as shown in Figure 1, in which 1 and 7 are input and output terminals, respectively, 2 and 4 are resistors, and 3
is a variable resistor, and 5 and 6 are capacitors. In such a tone control circuit, when the slider of the variable resistor is placed on the side of the capacitor 5, a low frequency enhancement characteristic is obtained, and when it is placed on the side of the capacitor 6, a low frequency attenuation characteristic is obtained. For example, resistor 2 and resistor 4
Assuming that the resistance value of , and the capacitance values of capacitor 5 and capacitor 6 are equal, and the slider of the variable resistor is placed in the electrically central position, the impedance between the input terminal and the output terminal and the impedance between the output terminal and ground are However, in reality, even if the slider of the variable resistor is placed in the mechanical center position, it will not be in the electrical center position due to variations, and completely flat characteristics cannot be obtained. Causes undulations in frequency characteristics. For this reason, if it is necessary to obtain completely flat characteristics, it is necessary to separately provide a default switch, resulting in a complicated structure and poor operability.

The present invention eliminates the above-mentioned drawbacks and provides a tone control circuit that can easily obtain flat characteristics.

The present invention will be described in detail below with reference to examples.

FIG. 2 shows an embodiment of the present invention. In FIG. 2, the input signal is at the non-inverting input terminal 19 of the amplifier 18.
The output of the amplifier 18 is connected to the output terminal 17 via a resistor 20 and is also applied to the inverting input terminal of the amplifier 18 via a negative feedback resistor 21. Further, the inverting input terminal of the amplifier 18 is connected to one terminal A of the variable resistor 12 via the resistor 11. The other terminal B and sliding terminal C of the variable resistor 12 are grounded. Further, one terminal A of the variable resistor 13 is connected to the output terminal 17 via the resistor 14,
The other terminal B and sliding terminal C are grounded. Further, capacitors 15 and 16 are connected between terminals A and B of each of variable resistors 12 and 13, respectively.

Here, the variable resistors 12 and 13 are made of a resistive material such as carbon between their mechanical midpoint D and one terminal B of each, as shown in FIG.
The space between the midpoint D and each other terminal A is made of a good conductor such as copper foil. Here, variable resistor 1
The sliding terminals C 2 and 13 are interlocked, so that when one slides on the copper foil part, the other slides on the resistor part, and at the mechanical midpoint, they both touch the copper foil part. It is arranged so that it is located on the foil part. Therefore, the resistance change characteristics between the respective terminals A and C of the variable resistors 12 and 13 described above are as shown in FIG. 4 by the solid line A and the dotted line B, respectively.

In the tone control circuit as described above, the resistance values of resistors 11 and 14 are R ₁₁ and R ₁₄ , and the total resistance values of variable resistors 12 and 13 are R 12 and R ₁₄ , respectively.
R ₁₃ , the above resistance values of the resistance values X and Y between each sliding terminal C and each terminal A of variable resistors 12 and 13
If the ratios X/R ₁₂ and Y/R ₁₃ to R ₁₂ and R ₁₃ are α and β, respectively, and the capacitance values of capacitors 15 and 16 are C ₁₅ and C ₁₆ , respectively, then the transfer function from input terminal 19 to output terminal 17 is H(jw) is α=0 when the slider of the variable resistor moves to the left of the mechanical midpoint D, so H(jw)=R ₁₁ +R ₂₁ /R ₁₁ ×R ₁₄ +βR ₁₃ /R ₁₄ +R ₂₀ +βR ₁₃ ×1+jwC ₁₆ (R ₁₄
βR ₁₃ )/1+jwC ₁₆ {(R ₁₄ +R ₂₀ )βR ₁₃ }...(1) A low frequency enhancement characteristic is obtained, and when the slider moves to the right of the mechanical midpoint D, β= Since 0, H(jw)=R ₁₁ +R ₂₁ +αR ₁₂ /R ₁₁ +αR ₁₂ ×R ₁₄ /R ₁₄ +R ₂₀ ×1+jwC ₁₅ {(R ₁₁
+R ₂₁ ) αR ₁₂ }/1+jwC ₁₅ (R ₁₁ αR ₁₂ )...(2) A low-frequency attenuation characteristic is obtained. Therefore, the transfer characteristics of the tone control circuit shown in FIG. 2 are illustrated in FIG. 5.

Next, when the slider is set at the mechanical midpoint D, α=β
=0, so H(jw)=R ₁₁ +R ₂₁ /R ₁₁ ×R ₁₄ /R ₁₄
+R ₂₀ (3) Since the influence of capacitors 15 and 16 is eliminated and completely flat characteristics are obtained, there is no need to provide a default switch in an audio amplifier or the like.

As described above, according to the present invention, the frequency characteristics can be changed by adjusting the variable resistor with a simple configuration, and the advantage is that completely flat frequency characteristics can be obtained at the mechanical center position of the variable resistor. You can get the same effect.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an example of a conventional tone control circuit, Fig. 2 is a circuit diagram showing an embodiment of the present invention, Fig. 3 is a circuit diagram showing a variable resistor used in the present invention, and Fig. 4 is a circuit diagram showing an example of a conventional tone control circuit. The figure is a diagram showing the resistance value change characteristics, and FIG. 5 is a diagram showing an example of the frequency characteristics of the tone control circuit according to the present invention. In the figure, 11, 14, 20 and 21 are resistors, 1
2 and 13 are variable resistors, 15 and 16 are capacitors, and 18 is an amplifier.

Claims (1)

[Scope of utility model registration request] In a tone control circuit having first and second variable resistors, both of the variable resistors are composed of a resistor part and a good conductor part, and a slider of one of the variable resistors slides on the resistor part. In position,
The slider of the other variable resistor is made to slide on a good conductor part, and at a predetermined position near the connection between the resistor and the good conductor, the sliders of both variable resistors are made to slide on the respective good conductor parts. It seems that the parts are sliding,
A capacitor is connected between both terminals of each of the variable resistors, one terminal of the variable resistors is grounded, and the other terminal is connected to the negative feedback terminal and output terminal of the amplifier, respectively. tone control circuit.