JPS644363B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an audio equalizer circuit with excellent characteristics.

The equalizer circuit for record playback signals provided in audio preamplifiers, etc., compensates for the characteristics when playing back music signals from records recorded with RIAA characteristics.
Equalizer element 1 having a circuit configuration as shown in the figure
It is configured with

The equalizer element 1 shown in FIG. 1 consists of a resistor 12 (value R1) and a capacitor 13 connected in parallel.
(value C1) and resistor 14 (value
R2) and a capacitor 15 (value C2) are connected in series, and the impedance Z between the terminals 10 and 11 is Z=1+S(R1R2)(C1+C2)/(1+
S・C1・R1) (1+S・C2・R2) (R1+R2)...(1) However, S=jω, where C1・R1=T _L =3180μs...(2) C2・R2=T _H = 75μs...(3) (R1R2)(C1+C2)=T _M =318μs...(4) Then, the impedance Z shown by the above equation (1) is
Transfer characteristic for RIAA compensation (RIAA compensation characteristic) GI, that is, G1=1+ST _M /(1+ST _L )(1+ST _H )...(5) Shows a transfer characteristic proportional to.

The conventional equalizer circuit uses the equalizer element 1 as described above, and the equalizer circuit shown in FIGS.
It had a circuit configuration as shown in the figure.

The equalizer circuit shown in FIG. 2 is a non-inverting amplifier composed of an amplifier (operational amplifier) 2, an equalizer element 1 (its impedance is Z) inserted in its feedback circuit, and a resistor 3 (value R3). It is a circuit, and its transfer characteristic G2 is G2=1+Z/R3...(6). Here, as is clear from equation (1), impedance Z has a sufficiently large value in the low frequency region, but approaches zero in the high frequency region, so the transfer characteristic G2 shown in equation (6) is In the low frequency range, it is approximately proportional to the RIAA compensation characteristic G1, but in the high frequency range, the value approaches "1" and the error increases. Furthermore, the equalizer circuit shown in Fig. 2 has the disadvantage that the amount of feedback increases and becomes unstable, especially in the high frequency range.To overcome this disadvantage, a resistor is inserted in series with the equalizer element 1 to limit the amount of feedback. Then,
Due to its resistance, its transfer characteristics and RIAA compensation characteristics
A problem arises in that the error with G1 increases further.

Next, the equalizer circuit shown in FIG.
and equalizer element 1 inserted in the feedback circuit.
(impedance Z) and input resistance 4 (value R4), its transfer characteristic G3 is G3=-Z/R4...(7), and the transfer characteristic of this equalizer circuit is G3 is
Although the sign is different from the RIAA compensation characteristic G1, it is proportional to the above-mentioned RIAA compensation characteristic G1. However, since this equalizer circuit outputs the input signal with its phase inverted, it is not suitable for audio amplifiers (especially 4-channel amplifiers), and it is not suitable for returning the inverted signal to the positive phase. Another extra inverting amplifier is required, which increases the cost. Also, the input impedance of this equalizer circuit is the input resistance 4
Since it is determined by the value R4 of input resistor 4, it is unsuitable for equalizer circuits that require high input impedance, and on the other hand, it increases the value R4 of input resistor 4.
The SN ratio will deteriorate.

This invention was made in view of the above-mentioned circumstances, and its purpose is to obtain a positive-phase output, which is suitable for audio use, and whose transfer characteristics are RIAA-compensated. The object of the present invention is to provide an equalizer circuit that is completely proportional to the characteristics and has stable operation.

To achieve this objective, the equalizer circuit according to the present invention is a non-inverting amplifier in which an impedance circuit Z having an equalizer element is inserted into a feedback circuit, and a resistor R is inserted between the feedback point and the ground point. The output of the circuit is supplied to a voltage dividing circuit having a transfer characteristic of Z/(Z+R), and the divided voltage in this voltage dividing circuit is taken out as an output.

Embodiments of the present invention will be described below with reference to the drawings.

First, the principle of operation of this invention will be explained. FIG. 4 is a circuit diagram showing the basic configuration of the present invention for explaining the operating principle of the present invention. In this figure, 2 is an amplifier (operational amplifier), its non-inverting input terminal is connected to the input terminal 10a, and the first equalizer element 1a (impedance is Z) is connected between the output terminal and the inverting input terminal. is inserted,
A resistor 3 (value R3) is inserted between the inverting input terminal and the common terminal 10b. Further, between the output terminal of the amplifier 2 and the common terminal 11b, a resistor 5 (its resistance value is n times R3) and a second equalizer element 1b (impedance is n times Z) are connected to the equalizer element 1b. They are inserted in series on the terminal 11b side. The connection point between the resistor 5 and the equalizer element 1b is connected to the output terminal 11a. Note that the common terminals 10b and 11b are short-circuited.

In the above configuration, reference numeral A in FIG. 4 is a non-inverting amplifier circuit in this basic configuration, which has the same configuration as the conventional equalizer circuit shown in FIG. Reference numeral B in FIG. 4 is a voltage dividing circuit newly provided in this invention.

In this configuration, the input terminal 10a
When the voltage signal vi is applied between the output terminal of the amplifier 2 and the common terminal 11b,
The voltage signal vx generated between the vi=1+Z/R3 (9), and this transfer characteristic is the same as the transfer characteristic G2 shown in equation (6) above. FIG. 5 is a frequency characteristic diagram showing the transfer characteristic of this non-inverting amplifier circuit A. As is clear from this figure, the transfer characteristic vx/vi approaches the value "1" in a high frequency region. The gain of this non-inverting amplifier circuit A for a DC voltage signal is (1+R1+R2/R3) since the impedance Z becomes a resistance value (R1+R2) for a DC signal.

Next, the transfer characteristics of the entire circuit with the basic configuration shown in FIG. 4 will be considered. Using the voltage signal vx mentioned above, the voltage signal vo generated between the output terminal 11a and the common terminal 11b is vo=nZ/nR3+nZ×vx...(10), and this equation (10) can be expressed as (8) By substituting the formula, vo=nZ/n(R3+Z)×R3+Z/R3×vi=Z/R3×vi (11) is obtained. From this equation (11), the transfer characteristic vo/vi of the circuit with the basic configuration shown in Figure 4 is vo/vi=Z/R3...(12), which is completely proportional to the RIAA compensation characteristic G1 mentioned above. I understand that there is. Figure 6 shows this transfer characteristic.
4 is a frequency characteristic diagram showing vo/vi, and as is clear from this diagram, the transfer characteristic of the circuit according to the basic configuration shown in FIG. 4 is completely proportional to the RIAA compensation characteristic over the entire frequency range. Note that the gain of the circuit with this basic configuration for a DC voltage signal is R1+R2/R3 from equation (12).

Next, a first embodiment of the present invention to which the above-described operating principle is applied will be described. FIG. 7 is a circuit diagram showing the configuration of the first embodiment of the present invention. In this figure, parts corresponding to those in FIG. 4 are given the same reference numerals. In FIG. 7, the configuration of this first embodiment differs from the basic configuration shown in FIG. 4 in that a resistor 6 (value
R6) is provided in parallel to reduce the output impedance, and the resistance value of the resistor 5 is accordingly changed to R5.

In the configuration shown in FIG. 7, the voltage signal vx at the output terminal of the amplifier 2 is (R3+Z/R3×vi), so the voltage signal vo at the output terminal 11a is vo=R3+Z/R3×R6nZ/R5+R6nZ×vi=R3+Z /
R3×R6・nZ/R5・R6+(R5+R6)・nZ×vi = R3+Z/R3×n・Z/R ₅・R ₆ /R ₅ +R ₆ +n・Z×
R6/R5+R6×vi...(13) Here, if (R5・R6/R5+R6) is set equal to n・R3, from this equation (13), the transfer characteristics vo/vi of the first embodiment shown in FIG. 7 are as follows: vo/vi=Z/R3 ×R6/R5+R6 (14) Since R3, R5, and R6 are all constants, it can be seen that the transfer characteristic vo/vi of this first embodiment is completely proportional to the RIAA compensation characteristic. Note that the gain for the DC voltage signal in this first embodiment is
R6((R1+R2)/R3(R5+R6).

Next, a second aspect of the present invention based on the above-mentioned operating principle.
An example will be explained. FIG. 8 shows the second embodiment of this invention.
FIG. 2 is a circuit diagram showing the configuration of an embodiment of the present invention. The configuration of this second embodiment is different from the basic configuration shown in FIG. is limited, and the resistance resistance 5
The point is that the resistance value of is changed to R5.

In the configuration shown in FIG. 8, the voltage signal vx at the output terminal of the amplifier 2 is (R3+R7+Z/R3×vi), so the voltage signal vo at the output terminal 11a is vo=R3+R7+Z/R3×nZ/R5+nZ× vi...(15) Therefore, the transfer characteristic vo/vi of this second embodiment is vo/vi=R3+R7+Z/R3×nY/R5+nZ...(16) where R5=n(R3+R0) If you set
Equation (6) becomes vo/vi=Z/R3 (17), and it can be seen from equation (17) that the transfer characteristic vo/vi of the second embodiment is completely proportional to the RIAA compensation characteristic. Note that the gain for the DC voltage signal in this second embodiment is R1+R2/R3.

Next, there is a third aspect of the present invention based on the above-mentioned operating principle.
An example of this will be explained. FIG. 9 is a circuit diagram showing the configuration of a third embodiment of the present invention. The configuration of this third embodiment differs from the configuration of the second embodiment described above in that a variable resistor 6 is provided in the second equalizer element 1b.
(value R6) are connected in parallel, and the sliding terminal of this variable resistor 6 is connected to the output terminal 11a.

The transfer characteristics vo/vi of this third embodiment are vo/vi=R3+R7+Z/R3×R6nZ/R5+R6nZ=R3+
R7＋Z／R3×nZ／R ₅・R ₆ ／R ₅ ＋R ₆ ＋nZ×R6／R5＋R6……
(18). Here, if R5・R6/R5+R6) is set equal to n(R3+R7), equation (18) becomes vo/vi=Z/R3×R6/R5+R6...(19), and the transmission of this third embodiment It can be seen that the characteristic vo/vi is completely proportional to the RIAA compensation characteristic. In this case, the gain for the DC voltage signal of this embodiment is R6 (R1+R2)/R3 (R5+R6).

For reference, in the third embodiment described above, the resistance value R1 of the resistor 12a is set to 15KΩ, the resistance value R6 of the resistor 6 is set to ∞, that is, open, and an equalizer circuit having a gain of 60 times for a 1KHz signal is realized. To do this, the resistance value R2 of the resistor 14a is 12436KΩ, the capacitance C1 of the capacitor 13a is 0.212μF, the capacitance C2 of the capacitor 15a is 0.0589μF, and the resistance value R3 of the resistor 3.
is set to 27.12Ω, and the resistance value R7 of resistor 7 is set to 135.5Ω.

As explained above, the equalizer circuit according to the present invention is a non-inverting amplifier circuit in which an impedance circuit Z having an equalizer element is inserted into a feedback circuit, and a resistor R is inserted between the feedback point and the ground point. The output is supplied to a voltage divider circuit with a transfer characteristic of Z/(Z+R), and the divided voltage in this voltage divider circuit is taken out as an output, so it has a transfer characteristic completely proportional to the RIAA compensation characteristic. A precise equalizer circuit can be realized. Further, the equalizer circuit according to the present invention is suitable as an equalizer circuit for audio because the phase of the output signal is in phase with the phase of the input signal, and is more suitable as an equalizer circuit for audio, compared to the conventional equalizer circuit in which the phase of the output is inverted. It has high input impedance, good signal-to-noise ratio, and low cost because no extra inverting amplifier is required. Furthermore, even if the amount of feedback in the non-inverting amplifier circuit is limited using a resistor, no error occurs in the transfer characteristics.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing the configuration of an equalizer element,
2 and 3 are circuit diagrams showing first and second configuration examples of a conventional equalizer circuit, FIG. 4 is a circuit diagram showing the basic configuration of the present invention, and FIGS. 5 and 6 are circuit diagrams showing the basic configuration of the present invention. 7 is a circuit diagram showing the configuration of the first embodiment of this invention. FIG. 8 is a circuit diagram showing the configuration of the second embodiment of this invention. FIG. 9 is a circuit diagram showing the configuration of a third embodiment of the present invention. 1a...first equalizer element, 1b...second
Equalizer element, 2... amplifier, A... non-inverting amplifier circuit, B... voltage dividing circuit.

Claims (1)

[Claims] 1. A non-inverting amplifier circuit in which an impedance circuit with an impedance value Z having an equalizer element is inserted in the feedback circuit, and a resistor with a resistance value R is inserted between the feedback point and the ground point, and Z/(Z+R) 1. An equalizer circuit comprising: a voltage dividing circuit having a transfer characteristic, wherein the output of the non-inverting amplifier circuit is supplied to the voltage dividing circuit and a divided voltage output is taken out.