JPS5880910A - Tone control circuit - Google Patents

Abstract

PURPOSE:To obtain a tone-controlled audio signal free of phase distortion among a low frequency, an intermediate frequency, and a high frequency component by providing an LPF and an HPF, a delay circuit the 1st and the 2nd multiplying circuits, and an adding circuit. CONSTITUTION:While a signal S11 as a low frequency component is supplied to a multiplying circuit 12, a control signal S13 is supplied from a control circuit 13 to the circuit 12 to control the signal S11 by the signal S13, and its output signal S12 is supplied to an adding circuit 3. While a signal S31 as a high frequency component is supplied to a multiplying circuit 32, a control signal S33 is supplied from the control signal 33 to the circuit 32 to control the signal S31 by the signal S33, and its output signal S32 is supplied to the adding circuit 3. Consequently, desired frequency characteristics are obtained and an LPF11 and an HPF31 generating both components S12 and S32 are composed of FIR type filters having symmetrical coefficients, so phase characteristics of the filters 11 and 31 are flat, so that there is no phase shift between the signals S12 and S32.

Description

DETAILED DESCRIPTION OF THE INVENTION Tone control circuits generally include:
It is composed of a combination of resistors. Therefore, if such a scene is hot in the total circuit, for example, the jth! II
If an audio signal having a high frequency component 8H and a low frequency component 8L is supplied as shown in
As shown in BK, the level of low frequency component 8L increases and at the same time, the phase shifts! In other words, phase distortion occurs.

The present invention aims to provide a tone control circuit that takes into consideration the phase of each signal component.

I will explain one example below.In the following example, as shown in jllll1311, the low range is 100.
It is a winding that can be adjusted over a range of ±10 dB over a range of ±10 dB, and the high frequency range can be adjusted over a range of ±10 dB over 15 kHz.

Fig. 1 KTh, Anada's audio signal is supplied to the rhythm/D-parter (2)K through the input terminal (1), and when the liquid number for one cycle is, for example, 60, it is number printed and sent to the digital Shinoki Shiko. This signal 82, converted t, is fed to a low-pass filter αυ.

This filter aυ is composed of 98 delay circuits D・~D-7, SO coefficient circuits al)~14-, and -49 addition circuits 4~4I, making up a 98th order oFrR whose coefficients are symmetrical. In other words, the delay circuits D. to D.1 are connected in cascade, the 0th delay circuit Do K signal 8s is supplied, and the nth (0<II<49) and (1151-
11) If the output of the first delay circuit is (
49-ym)-th coefficient circuit 141-EI K is supplied, the signal 81 and the output of delay circuit D. is supplied to the coefficient circuit MO”'-84
The output of 8 is supplied to the adder circuit 4 to 48K and the signal St
t is taken out.

In the case of M, the evacuation time of the delay circuit D to D is M/D;
Inverter (2) The reciprocal of the sampling frequency at K,
In other words, it is 20 microseconds. Also, the coefficient aha・~
The 149 coefficients are selected as shown in FIG. 8, for example. In addition, in Figure 8, the number following the letter E is
It shows the multiplier of 1G, for example, the coefficient of coefficient circuit 1 (H is lemLi1m08I-3 film tismosx1o-"). Therefore, the frequency characteristic of filter convergence υ is a low-pass 1-pass as shown in Fig. 6. Characteristics (stopband loss is 47 dB or more)
The output signal 8o is the low frequency component of the input signal of the terminal (1).

Then, the signal 811 of this image area component is supplied to the multiplication circuit azk, and the control signal 8ss is supplied from the control circuit a3 to the multiplication circuit aaK. controlled by
Its output signal 81! is supplied to the adder circuit (3).

Further, the signal 82 from the converter (2) is transmitted to the delay circuit Ql
The adder circuit (3)K is supplied through the adder circuit (3)K. This delay circuit Q
1 is the signal 8 and the signal supplied to the adder circuit (3) K.

This is to eliminate the difference in the delay time from 81*, and for this reason, the delay circuit a! Reference numeral 9 is composed of four delay circuits D41 similar to the delay circuit DIG in the filter a1).

Furthermore, a signal 8m is taken out from the delay circuit I)4t of the filter t21), and this signal 82 is supplied to the 1no bus filter 111)K. This filter 61) is also constructed in a third-order FIR type with symmetrical coefficients, and includes delay circuits D., Dl, coefficient circuits b., bl, and an adder circuit B.

and has. Note that the coefficients of the coefficient circuit bOe bl are selected as shown in FIG. 9, for example.

Therefore, the frequency characteristic of the filter 600 becomes a high-pass characteristic (stopband loss is 5411B or more) as shown in FIG. 1, and its output signal SSt is a high-frequency component of the input signal at the terminal (1). Also, this signal 831.

Adder circuit (3) K supplied signal 811 #8m
There is no difference in transfer time between the two.

Then, this high-frequency component signal SSt is transmitted to the multiplier circuit (2) K
At the same time, the control signal all is supplied from the control circuit (to).
is supplied to the multiplier circuit (2) K, and the signal 831 is the signal 5SS.
The level of signal ssi is controlled by k as shown in FIG. 6, and the output signal SSS is supplied to adder circuit (3)K.

Therefore, from the adder circuit (3), the signal all e '1
The addition signal 8m of m'11 is taken out, and this signal 83 has a liquid number characteristic as shown in the 3rd HK.

In other words, the level of the low frequency component 81m changes from 5lsK to 5 as shown in Figure 4, and this low frequency component 8
11 is added to the flat s-character signal 83, the image area component its which meets the summed signal 8mK changes as shown in FIG. In addition, the higher frequency component 8 from the control signal ass K
11f) The level changes to 5 as shown in FIG. 2, and this high frequency component 881 is added to the signal 83 with flat characteristics.
Change as shown. Therefore, the signal also becomes the control signal 81
From 1 m s,,K, the peripheral liquid number characteristic changes as shown in Fig. 3.

Then, Jin's signal 4#8s is supplied to the D/mukon perme (4) and made into an analog 1w da audio signal, which is taken out from the output terminal (5)K.

Furthermore, according to the present invention, tone punching of an audio signal is possible. In this case, in particular, according to this invention, a low frequency component "11" and a high frequency component SSS are added to a signal 83 with a flat characteristic. While adding up to obtain the desired circumaxillary number,
At this time, both components 811 e 'l! Since the filters αυ and clυ that form the filter αυ and clυ are composed of FIR type filters with symmetrical coefficients, the filter αυ.

The phase characteristics of the tA intuition become flat, and the signal S1'1m
K phase shift does not occur, and the follow [, terminal (5
), there is no phase shift, that is, no phase distortion, between the low frequency component 8tz, middle frequency component, and high frequency component 8n included in the output signal Kt.

In the example shown in FIG. 10, the phase (delay) of the low, middle, and high ranges can also be adjusted.

That is, a low frequency component 811 from the filter αυ and a signal 8 with flat characteristics from the delay circuit Qυ! and filter a1
) is supplied to the subtraction circuit (6)K, and both components '11s Sm1 are subtracted from the signal S3.
A midrange component S. is extracted. So, each of these ingredients 8
1h8・, 831 are supplied to variable delay circuits I, (goods), and C%, and the delay times of delay circuits I to (goods) are controlled by control signals from control circuits (15, (c), &9), respectively. be done.

And, 〼l! The low frequency component 811 from circuit a4 is multiplied by I
I jl am K is supplied, and the mid-range component S6 from the one-way circuit is supplied to the adder circuit (3), and the high-frequency component 831 from the delay circuit is supplied to the multiplier circuit (to) k. be done.

Therefore, at the terminal (5) k, a tone-controlled audio signal is extracted, and the delay of each band component is adjusted to a desired magnitude.

[Brief explanation of drawings]

Figures 1 and 10 are phylogenetic diagrams of an example of Jin, and Figures 2~
The ninth WA is a diagram for explaining the same. I is an m-pass filter, and Gυ is a bypass filter t.

Claims (1)

[Claims] an FIR type m-pass filter with symmetrical coefficients, to which a digital signal A/D converted from an audio signal is supplied;
The digital signal is supplied to a FIR-type no-pass filter with symmetrical coefficients, and a second filter that controls the output of the one-pass filter to control the level of the signal component when the output is D/MU-converted. a second multiplier circuit that controls the output of the no-pass filter to control the level of a signal component when this output is D/mu-converted; and an output of the l-th multiplier circuit. and an adder circuit for adding the output of the second multiplier circuit and a digital signal having at least a mid-range component of the audio signal, and a digital signal of the tone-controlled audio signal is output from the adder circuit. Tone control circuit designed to bring out