JPS6240883B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a frequency characteristic correction circuit (hereinafter referred to as a correction circuit). (Prior Art) As a conventional correction circuit, for example, a high frequency correction circuit as shown in FIG. 3 has been known. In the figure, 21 is an input terminal 22, 24 is a resistor, 23 is a volume,
26 and 27 are capacitors, and 25 is an output terminal. In this case, the phase characteristics at the output terminal 25 are:
As shown in FIG. 2, the phase is 0° at low and high frequencies, but the phase changes significantly at mid-range frequencies depending on the setting position of the volume 23. (Problem to be Solved by the Invention) Therefore, in an audio amplifier or the like having two left and right channels, if a correction circuit as described above is inserted for each channel, the phase difference will also change depending on the characteristic settings of each correction circuit. Because they are different as shown in Figure 2,
At mid-range frequencies, the phase difference between the left and right channels becomes very large. (Objective) An object of the present invention is to provide a correction circuit that does not have the above-mentioned drawbacks, and will be described in detail below with reference to the drawings. (Embodiment) FIG. 1 shows an embodiment of a high frequency correction circuit according to the present invention. In the figure, the input signal applied to the input terminal 1 is branched into two, one being applied to the inverting terminal 6 of the broadband amplifier 4 via the resistor 2, and the other being applied to the inverting terminal 6 of the wideband amplifier 4 via the variable resistor 8 and the capacitor 9. and is applied to the non-inverting terminal 7 of the broadband amplifier 4. amplifier 4
The output of is connected to the output terminal 5 and fed back to the inverting terminal 6 via the variable resistor 3. Further, the variable resistors 3 and 8 are interlocked.
In such a circuit, the resistance value of resistor 2 is now R ₀
Assuming that the resistance setting values of variable resistors 3 and 8 are KR ₀ and R, respectively, the capacitance of capacitor 9 is C, and the angular velocity of the input signal is ω, the transfer function G(jω) of this circuit is G(jω) =1−jωKCR/1+jωCR
...(1) Therefore, this phase characteristic arqG(jω) is arqG(jω) = -(tan ^-1 KωCR +tan ^-1 ωCR) ...(2) Now the phase becomes 90° at the point where the angular velocity ω becomes ω ₀ . Then, the time constant CR of the voltage divider circuit is given by equation (2). becomes. Now, by substituting equation (3) into equation (1) and finding the amplitude characteristic, Then, the phase characteristic in this case is obtained by substituting equation (3) into equation (2). becomes. Therefore, if the time constant CR of the voltage divider circuit is changed in accordance with the change in K so as to maintain the relationship of equation (3), the amplitude characteristic will be changed according to equation (4) according to each value of K. It can be seen that it changes and becomes as shown in Figure 4. Note that since the value of K is equal to the degree of amplification for the high frequency range, it is converted into decibels and shown in the figure. In addition, the phase characteristics change according to equation (5) according to the value of K, as shown in Figure 5,
In the low range of angular velocity, it is approximately 0°, at angular velocity ω ₀ , it is -90°, and in the high range, it is approximately -180°, and this relationship does not change even if the value of K is changed. In areas other than the three frequency points mentioned above, slight fluctuations in phase characteristics occur depending on the value of K, but there is no large fluctuation in phase as in the conventional example shown in Figure 2. . FIG. 6 shows that K is 3.16 (+10 db) or 1/3.16 (-
10db) and K is 2 (+6db) or 1/2 (-
6db), and it can be seen that in this case, only a maximum phase difference of about ±4.5° occurs. Therefore, in a multi-channel amplifier, if a correction circuit like the one described above is used for each channel, the phase difference between each channel will be very small even if the adjustment states of these correction circuits are set independently of each other. Recognize. FIG. 7 shows an embodiment of the low frequency correction circuit according to the present invention. That is, in this embodiment, the connection between the capacitor 9 and the resistor 8 of the voltage dividing circuit in the embodiment shown in FIG. Further detailed explanations of the reference numerals and configurations will be omitted. The transfer function G(jω) of such a circuit is G(jω)=K−jωCR/1+jωCR…
(6), and the phase characteristic arqG(jω) becomes arqG(jω)=tan ⁻¹ ωCR/K+tan ⁻¹ ωCR (7). Therefore, if we assume that the phase is 90° at the point where the angular velocity ω becomes ω ₀ , the time constant CR of the voltage divider circuit is given by equation (7). Then, substituting equation (8) into equation (6), we get Also, substituting equation (8) into equation (7), we get becomes. Therefore, as in the case of the embodiment shown in FIG.
If we change them in conjunction to maintain the relationship in equation (8), we get
The change in amplitude characteristics with respect to the value of K is as shown in FIG. The phase characteristics are as shown in Figure 9, approximately 180° in the low frequency range and 90° at the angular velocity ω ₀ .
In the high range, it is approximately 0°, and this relationship does not change even if the value of K is changed. Although a slight change in phase occurs depending on the value of K in areas other than the above-mentioned three points, this change is very small as in the embodiment shown in FIG. Figure 10 shows that in this example, K is 3.16 (+10db) or 1/3.16 (-
10db) and K is 2 (+6db) or 1/2 (-
6db). In the above embodiments, the capacitance C of the capacitor 9 is fixed, and the resistance value of the variable resistor 8 is inversely proportional to √ in the embodiment shown in FIG. 1, and directly proportional to √ in the embodiment shown in FIG. However, the resistance value R may be fixed and the capacitance C may be set to be inversely proportional to √ in the case of FIG. 1, and directly proportional to √ in the case of FIG. For example, in the case of Fig. 1, the value of each K of resistor 3
K ₁ K ₂ ...Resistance value corresponding to K _o K ₁ R ₀ , K ₂ R ₀ ... K _o R ₀
is changed by a changeover switch, and the resistance value R of resistor 8 is changed by a changeover switch linked with this.

It is also possible to switch as shown in [Formula]. The same applies to the case of FIG. Note that the angular velocity ω ₀ can be easily changed by changing the value of the capacitance C or the resistance R, which is fixed in the above. The value of K can also be changed by using a variable resistor as the input resistor 2. In this case, the input resistor 2 and, for example, the variable resistor 8 may be made variable in conjunction with each other. (Effects) As described above, according to the present invention, even if the adjustment states of the respective frequency characteristic correction circuits are different, the phase difference between channels is small, so it is possible to eliminate uncertainty in sound image localization.

[Brief explanation of the drawing]

Fig. 3 shows a conventional frequency characteristic correction circuit, Fig. 2 shows its phase characteristic diagram, Fig. 1 shows a circuit diagram of an embodiment of the present invention, and Figs. 4, 5, and 6 show its characteristics. FIG. 7 is a circuit diagram showing another embodiment of the present invention, and FIGS. 8, 9, and 10 are diagrams showing its characteristics. 3, 8...variable resistor, 14...wideband amplifier.

Claims (1)

[Claims] 1 A voltage divider consisting of a differential amplifying means having first and second input terminals, an input resistor for applying an input signal to the first input terminal, and a series-connected circuit of a resistor and a capacitor for dividing the voltage of the input signal. a circuit, means for connecting a connection point between the resistor and the capacitor to the second input terminal, and negative feedback means for negatively feeding back the output of the differential amplification means to the first input terminal; A frequency characteristic correction circuit characterized in that the time constant of the series connection circuit of the resistor and the capacitor and the feedback coefficient of the negative feedback means are variable in conjunction with each other.