JPS6038896B2 - Frequency characteristic correction circuit - Google Patents

Description

[Detailed description of the invention] The present invention relates to a frequency characteristic correction circuit (hereinafter referred to as a correction circuit).

) regarding. As a conventional correction circuit, for example, a Takagi correction circuit as shown in FIG. 1 has been known.

In the figure, 21 is an input terminal 22, 24 is a resistor, 23 is a volume, 26, 27 is a capacitor, and 25 is an output terminal. In this case, the phase characteristic at the output terminal 25 is
As shown in the figure, the phase is 00 at the low frequency and Takagi frequency, but the phase changes significantly depending on the setting position of the volume 23 at the Nakagusuku frequency. Therefore, in an audio amplifier having two left and right channels, if a correction circuit as described above is inserted for each channel, the phase difference will differ as shown in Figure 2 depending on the characteristic settings of each correction circuit. In terms of frequency, the phase difference between the left and right channels becomes very large.

An object of the present invention is to provide a correction circuit free from the above-mentioned drawbacks, and will be described in detail below with reference to the drawings.

FIG. 3 shows an embodiment of the Takagi correction circuit according to the present invention.

In the figure, the input signal applied to the input terminal 1 is branched into two branches, one being connected to the inverting terminal 6 of the broadband amplifier 4 via the resistor 2.
and the other is applied to the non-inverting terminal 7 of the broadband amplifier 4 via a voltage divider circuit including a variable resistor 8 and a capacitor 9. The output of the amplifier 4 is connected to an output terminal 5 and fed back to an inverting terminal 6 via a variable resistor 3. Also, variable resistors 3 and 8 are put into motion.

In such a circuit, let the resistance value of resistor 2 be Ro,
Let the resistance setting values of the variable resistors 3 and 8 be KRo and R, respectively, the capacitance of the capacitor 9 be C, and the angular velocity of the input signal be w, then the transfer function G(W) of this circuit is GM=Mikasaso R.・・・．・Accordingly, this phase characteristic argG(jw) is arg○(iw)=1(tan[IKwCR+nen-I
WCR),. ．． 、． ．． ■If we assume that the phase becomes 900 at the point where the speed w becomes wo, the time constant CR of the voltage dividing circuit is 1. ．．・
...'3'CR = both rain.

Now, by substituting equation {3} into equation {1-, the amplitude characteristic is obtained, and in this case, the phase characteristic is obtained by substituting the lake equation into equation '2} to obtain argG(iW)=-tan-1 party K. -tan-・(
Rare)・R・…side.

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 change according to the equation (2) according to each value of K, and the fourth You can see that it looks like the figure.

Note that since the value of K is equal to the degree of amplification with respect to Takagi, it is converted into decibels and shown in the figure. In addition, the phase characteristic changes according to the equation '5} according to the value of K, as shown in Figure 5, and in the low range of angular velocity it is approximately oo and -90 at angular velocity wo.
o, it becomes approximately -1800 in the high range, 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. . Figure 6 is based on the case where K is 1 in the above embodiment.
．． In the case of 16 (11 melon b) bases (-IMb) and K is 2
It shows the change in characteristics in the case of (10 mob) or gei (-&&), and it can be seen that in this case, only a maximum phase difference of about 4.50 occurs.

Therefore, in a multi-channel amplifier, if a correction circuit such as the one described above is used for each channel, it can be seen that even if the adjustment states of these correction circuits are set independently of each other, the phase difference between each channel will be very small. .

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. A more detailed explanation of the reference numerals and configurations will be omitted. The transfer function G(fu) of such a circuit is G(
f)=・K-WCR,.・．． ...{611
1jwCR, and the phase characteristic argG(jw) is argG(iW)=tan-・Scale side...R...'
7).

Therefore, at the point where the angular velocity w becomes wo, the phase is 900
Assuming that, the time constant CR of the voltage divider circuit is given by formula [7} as CR=--ZR...
...'8}Wo, and substituting the {8} formula into the {6) formula, and substituting the shelf formula into the [7} formula, argG(iW)=tan-1 false unpublished n-・billion no K--
‐‐‐‐{It becomes IQ.

Therefore, as in the case of the embodiment shown in FIG. The change in characteristics is as shown in Figure 8.The phase characteristic is as shown in Figure 9, with an angular velocity of approximately 1800 and an angular velocity w in the low frequency range.
is almost 00 in the 900 high range, and this relationship does not change even if the value of K is changed. In areas other than the three points mentioned above, a slight change in phase occurs depending on the value of K, but as in the embodiment of FIG. 3, this change is very small.

Fig. 10 shows the case of ■ 3.16 (10 IMb) or 'Matai ('Mb)', based on the case where K is 1 in this embodiment, and
It shows the variation in phase characteristics when K is 2 (Jukoku b) or Kyo (Issei b).

In the above embodiments, the capacitance C of the capacitor 9 is fixed, and the resistance value of the variable resistor 8 is made inversely proportional to K in the embodiment shown in FIG. 3, and to K in the embodiment shown in FIG. Although they are set to be directly proportional to each other, it is also possible to fix the resistance value R and set the capacitance C to be inversely proportional to K in the case of Figure 3, and directly proportional to K in the case of Figure 7. good.

For example, in the case of FIG. 3, the values of each K of the resistor 3 are K,,K2・
...Resistance value K,, Ro, K2Ro...Kn corresponding to Kn
Ro is changed over by a changeover switch, and the resistance value RI 1 end W of the resistor 8 is changed by the changeover switch interlocked with this changeover switch.

A woman of c. It's a good idea to switch quickly.

C side lol. You may choose Mr. C.

The same applies to the case of FIG.

Note that the angular velocity wo can be easily changed by changing the value of the capacitance C or the resistance R 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. As described above, according to the present invention, even if the adjustment states of the frequency characteristic correction circuits are different from each other, the phase difference between channels is small, so that uncertainty in sound image localization can be eliminated.

[Brief explanation of the drawing]

Fig. 1 is a conventional frequency characteristic correction circuit, Fig. 2 is a phase characteristic diagram thereof, Fig. 3 is a circuit diagram showing an embodiment of the present invention, and Fig. 4 is a circuit diagram showing an embodiment of the present invention.
Figures 5 and 6 are line diagrams showing its characteristics, Figure 7 is a circuit diagram showing another embodiment of the present invention, and Figures 8, 9 and 10 are line diagrams showing its characteristics. It is a diagram. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10

Claims (1)

[Claims] 1 differential amplification means having first and second input terminals;
A first for applying an input signal to the first and second input terminals.
and a second input resistor, a capacitor for grounding 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 a time constant formed by a resistor and a capacitor and a feedback coefficient of the negative feedback means are variable in conjunction with each other.