JPH0533064Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an equalizer circuit that can be applied to a graphic equalizer circuit in a speaker system or the like.

[Summary of the idea]

The present invention has a damping characteristic and a boosting characteristic for a predetermined center frequency, and by making the resonance sharpness of the damping characteristic higher than the resonance sharpness of the boosting characteristic, the howling prevention effect and tone control effect are respectively improved. It was designed to let you do so.

[Conventional technology]

Conventionally, graphic equalizer circuits having vertically symmetrical characteristics as shown by curves a and b in FIG. 5 have been known. In the figure, curve a is a boost characteristic having a predetermined resonance sharpness Q with respect to the center frequency ₀ , and curve b is a cut characteristic (damping characteristic) having the above-mentioned ₀ and Q. curve a,
The Q of b is usually selected to be about 1.5, and the boost and attenuation amounts are ±12 db.

FIG. 6 shows a graphical equalizer circuit having the above characteristics, which includes an input terminal 1 to which an input signal e _i is supplied, a coupling capacitor C ₁ , an input resistor R ₁ , an operational amplifier 2, a feedback resistor R ₃ , an input terminal and It is composed of a feedback variable resistor R ₂ , an impedance Z, an output terminal 3 from which an output signal e ₀ is obtained, and the like. Impedance Z is constituted by a series resonant circuit consisting of capacitance Xc, inductance X _L , and resistance X _R. The middle point of the variable resistor R ₂ is grounded, one end is connected to the non-inverting input terminal of the operational amplifier 2, the other end is connected to the inverting input terminal of the operational amplifier 2, and the middle point of the movable element 4 is connected to the non-inverting input terminal of the operational amplifier 2. The characteristics of curve b can be obtained by adjusting the side, and the characteristics of curve a can be obtained by adjusting from the midpoint to the inverted input side.

Such a graphic equalizer circuit is installed, for example, between a microphone amplifier and a power amplifier, and uses its boost side curve a to mainly perform tone control, and its cut side curve b to mainly prevent howling. There is.

[Problem that the invention attempts to solve]

In the conventional graphic equalizer circuit described above, a fifth filter is used to increase the howling prevention effect.
As shown by the dotted line c in the figure, when Q is increased, the tone control effect on the boost side deteriorates. Therefore, we set Q≒1.5 as low as possible so as not to damage the tone control effect, but in that case,
On the cut side, when howling is prevented, the sound quality will be impaired in the shaded area.

[Means for solving problems]

In the present invention, means is provided for making the resonance sharpness of the damping characteristic higher than the resonance sharpness of the boosting characteristic.

[Effect]

For example, the boost characteristics and cut characteristics are vertically asymmetrical as shown in Figure 1, and the cut side with a high Q can sufficiently prevent howling without affecting the sound quality, while the boost side with a low Q can provide tone control. You can get the full effect.

〔Example〕

As shown in FIG. 1, the equalizer circuit according to the present invention is designed to obtain a boost side curve a and a cut side curve b that are vertically asymmetrical with respect to the center frequency ₀ . In this case, for example, curve a is Q≒1.5
The boost amount is +6dB, and curve b is Q≧2.
~2.5, the attenuation is -12dB.

According to the equalizer circuit having the above characteristics, the howling prevention effect can be improved by the curve b without deteriorating the sound quality, and the tone control effect can be obtained by the curve a.

FIG. 2 shows an embodiment of an equalizer circuit for obtaining the characteristics shown in FIG. 1, and parts corresponding to those in FIG. 6 are given the same reference numerals.

In this example, the resistors R ₃ and R ₂ in the circuit of FIG.
A new resistor _R4 is added between the
Figure 3 shows an equivalent circuit when the movable element 4 of the variable resistor R2 in Figure ₂ is adjusted on the boost side, and Figure 4 shows an equivalent circuit when the movable element 4 is adjusted on the cut side. It is.

In FIGS. 3 and 4, two resistors R ₂ /2, which are obtained by dividing the variable resistor R ₂ into 1/2 from the midpoint, are connected to the plus side and the minus side of the operational amplifier 2, respectively. In that case, in Fig. 3, R ₂ /2 connected to the positive side of operational amplifier 2 becomes a fixed resistance, and in Fig. 4, R ₂ /2 connected to the negative side of operational amplifier 2 becomes a fixed resistance. connected in series with resistor _R4 .

In the case of Fig. 3, impedance Z is connected to the movable element 4 with a resistance R ₂ /2 on the negative side, and if the resistance value from the midpoint to the movable element 4 is A, then the above Z, R ₂ /2 and The composite impedance Z ₀ of R ₄ is
Z ₀ =A・Z (A+Z)+R ₂ /2−A+R ₄ .
However, A satisfies 0≦A≦R ₂ /2. On the contrary,
In the case of FIG. 4, impedance Z is connected to the mover 4 with a positive resistance R ₂ /2, and if the resistance value from the midpoint to the mover 4 is B, then the above Z and
The composite impedance Z ₀ of R ₂ /2 is Z ₀ = B・
Z/(B+Z)+ _R2 /2-B. However, B is 0
≦B≦R ₂ /2. This composite impedance cooperates with R ₁ to form a voltage divider circuit.

By adding _R4 , the Q during boost can be made lower than the Q during cut. Therefore, Q at the time of cutting is determined by curve b in Fig. 1.
As shown in the figure, if you choose the high value necessary to prevent howling, you can arbitrarily set the size of Q to obtain the required boost amount of curve a by choosing the size of resistance _R4 . becomes.

In addition, conventional variable resistors _R2 have been made to have a resistance value change curve with respect to the position of the knob having a special W curve or a 5B curve, so that the relationship between the position of the knob and the tone control characteristics is close to linear. However, the characteristics were not sufficiently linear, making it difficult to perform fine tone control.

In this embodiment, since the resistor _R4 is connected in series with the impedance Z during boosting as shown in FIG. 3, the linear characteristics described above are improved compared to the conventional one, and fine tone control can be performed depending on the position of the volume knob. It can be performed. In addition, the size of each resistance R ₁ , R ₂ , R ₃ , R ₄ is, for example, R ₂ =
250kΩ, R ₁ , R ₃ = 1.5kΩ, R ₄ = 750Ω.

[Effect of idea]

Since the Q of the boost characteristic and the Q of the cut characteristic for a predetermined center frequency can be determined separately with one equalizer circuit, it is possible to increase the howling prevention effect without impairing the sound quality, and also obtain a tone control effect. Can be done.

[Brief explanation of the drawing]

Fig. 1 is a characteristic diagram of an equalizer circuit showing an embodiment of the present invention, Fig. 2 is a circuit diagram showing an embodiment of the invention, Fig. 3 is an equivalent circuit diagram of Fig. 2 during boosting, and Fig. 4 is FIG. 2 is an equivalent circuit diagram at the time of cutting, FIG. 5 is a characteristic diagram of a conventional graphic equalizer circuit, and FIG. 6 is a circuit diagram of a conventional graphic equalizer circuit. In addition, in the symbols used in the drawings, 2... operational amplifier, R ₃ , R ₄ ... resistor, R ₂ ... variable resistor, Z
...impedance.

Claims (1)

[Claims for Utility Model Registration] An operational amplifier, a feedback resistor connected between the output terminal and the inverting input terminal of this operational amplifier, and a variable resistor whose midpoint is grounded and whose one end is connected to the non-inverting input terminal of the operational amplifier. an equalizer circuit comprising: a resistor connected between the other end of the variable resistor and the inverting input terminal; and a series resonant circuit connected to a movable element of the variable resistor.