JPS581799B2 - Tone control device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a timbre control device that changes the timbre of a musical tone signal such as an electronic musical instrument, and in particular, a timbre control device that significantly changes the resonant frequency of two or more resonant filters. It is something.

Conventionally, two resonant filters were placed in parallel to create a resonant peak at an arbitrary frequency with a steep transmission characteristic, and the resonant frequencies of the two resonant peaks were made independently of each other within the audible range. A tone control device that can change the tone color is known.

In this case, the resonant frequency is freely set by two 11-variable resistors, a so-called 4-channel volume or a joystick, which moves an operating rod in two dimensions.

However, in conventional tone control devices, the resonance characteristics of the two resonance filters and the changes in these resonance characteristics depending on the resonance frequency are configured to change in exactly the same way.

For example, if the resonant frequency of the first resonant filter is f1 and the resonant frequency of the second resonant filter is f2, then f1=
When setting fa, f2=fb and f1=fb, f2
=fa, the overall frequency characteristics are exactly the same.

That is, there is a drawback that the tone becomes the same even though the position of the operating device is different.

The present invention provides a timbre control device that eliminates these drawbacks.

FIG. 1 is a block diagram showing the principle of the invention.

In Fig. 1, a plurality of filters 3 and 4 (
In the case of Fig. 1, two filters are arranged in parallel, and a musical sound signal S1N is applied from input terminal 1 to filters 3 and 4, and output signals S1 and S2 of each filter 3 and 4 are added by adder 5. , output signal S0
is obtained at the output end 2.

The resonance frequencies f1 and f2 of the resonance peaks of the filters 3 and 4 can be independently varied by operating a variable resistor such as a slide volume with the operation device 6.

At least one of the gains G1 and G2 at the resonance peaks of the P-wave devices 3 and 4 and the resonance Q1 and Q2 has a resonance frequency f
1, changes as f2 changes.

Furthermore, the filters 3 and 4 are made to have different relationships between gain and Q change with respect to the resonance frequency.

For example, G1 and Q1 are proportional to f1, and G2 and Q2 are proportional to f1.
Make it inversely proportional to 2.

Here, proportionality and inverse proportion simply refer to the relationship of increase and decrease, and mathematical rigor is not necessarily required.

An example of such a filter is shown in FIG.

FIG. 2a shows a musical tone signal applied from the input terminal 10 through the resistor R1, and a signal outputted from the output terminal 11 by dividing the voltage between the parallel resonant circuit in which the capacitor C1 and the inductor L1 are connected in parallel and the resistor R1. It is taken out as

The capacitance (C1) of the capacitor C1 can be changed by the operating device 6.

Figure 2b shows resistor R2, capacitor C2, and inductor L.
2 are connected in the same manner as in Fig. 2a.

However, the inductance (L2) of the inductor L2 can be changed by the operating device 6.

The resonance frequencies of Figure 2 a and b are f1 and f2, respectively, G1 and G2 at the resonance peak, respectively, and the Q of the resonant circuit is Q, respectively.
1 and Q2, the following equation holds between them.

From these equations, the gains G1 and G2 at the resonance peak are one, Q1 is inversely proportional to f1, and Q2 is proportional to f2.

FIG. 3 shows an example of the frequency diagram characteristics, where the broken line represents the characteristics of the filter shown in FIG. 2a, and the solid line represents the characteristics of the filter shown in FIG. 2b.

Therefore, two types of overall characteristics can be realized: a combination of the solid line A and the broken line 2, or a combination of the solid line A and the broken line C.

Of these two cases, the former is a case where there are two resonance peaks with a small Q, and the latter is a case where there are two resonance peaks with a large Q.

In the conventional device, these two characteristics were exactly the same, but in this embodiment, the characteristics are different and different tones can be obtained.

Therefore, the conventional problem of the overall frequency characteristics being the same despite the different positions of the operating devices is completely eliminated, unnecessary control is reduced, and the degree of freedom in timbre control is increased.

FIG. 4 shows another example of the filters 3 and 4.

Only the differences from FIG. 3 will be explained. Resistors r1 and r2 are connected in series to inductors L1 and L2 of each filter.

The resonant frequencies f1 and f2 for Fig. 4 a and b are respectively
When the resonance Q is Q1 and Q2, respectively, and the impedance of the parallel resonant circuit is Z1 and Z2, the following equation holds between them.

Therefore, in the filter of FIG. 4a, Q1 and the gain at the resonance peak (=Z1/(Z1+R1)) are proportional to the resonance frequency f1.

On the other hand, in the filter shown in Figure 4b, Q2 and the gain at the resonance peak (
=Z2/(Z2+R2)) is inversely proportional to the resonance frequency f2.

This situation is shown in FIG.

The solid lines in FIG. 5 represent the characteristics of the filter of FIG. 4a, and the broken lines represent the characteristics of the filter of FIG. 4b.

In this case as well, by combining the solid line and the broken line, it is possible to realize a variety of efficient frequency characteristics.

Note that the same effect can be obtained by using an equivalent inductance circuit using an electronic circuit such as a gyrator in place of the inductors L1 and L2.

By the way, in the tone control device shown in FIGS. 1 to 5,
Due to the resonance characteristics of each of the wavers 3 and 4, the frequency characteristics can only be varied in a relatively narrow band, and the Q setting range is also limited to a narrow range.

The present invention solves these problems and provides a timbre control device that can vary the frequency characteristics over a wide range over the entire audio frequency band, and can also vary the Q over a wide range, making it easy to design. be.

An embodiment of the present invention will be described below with reference to FIGS. 6 and 7.

FIG. 6 shows the specific structure of the filters 3 and 4 in the principle diagram of FIG. 1.

In FIG. 6, the musical tone signal applied to the input terminal 16 is transmitted to the all-pass circuit 21 via the buffer 17 and the resistor R3.
．． 22 and a phase inverter 23 in series.

The output signal of the phase inverter 23 is transmitted through a resistor R5 and a variable resistor R4.
The signal is returned to the input of the all-pass circuit 21 via.

The all-pass circuit 21 has a transfer function 01(S) with the following characteristic: G1(S)=-(S-So)/(S+So), and is commonly known as a Toulon circuit.

It constitutes an all-pass circuit. And its transfer function G
2(S) becomes.

Therefore, the phase shift is -180 at the frequency S=So.
The phase inverter 23 changes the phase to +180°.

In other words, the return becomes a stop return.

Therefore, resonance occurs at S=So. An output signal is taken out from an input terminal of the all-pass circuit 21 via a buffer 24 and an output terminal 27.

The Toulon circuit is as shown in FIG. 7, in which the signal supplied to the terminal 28 is added to the differential output amplifier 29 to generate two signals of positive phase and negative phase, and is connected to the capacitor C3 and the resistor R6.
Mixing is performed at the output terminal 30 via the .

When the resistance R6 is changed, the above So is changed.

If So=J2πfo, ,fo=1/2πR6C3
become.

Therefore, in FIG. 6, all-pass circuits 21 and 22
By changing the adhesive resistances 25 and 26, So can be changed and the resonance frequency can be changed.

Further, when the amount of feedback is changed by the variable resistor R4, the Q of resonance changes.

Therefore, by interlocking the town variable resistance 25, 26 and the town variable resistance R4, it becomes possible to change the resonance frequency f and G at the resonance peak in relation to each other.

When the resistance values of the variable resistors 25, 26, and R4 are changed proportionally, the resonance frequency f and the gain G become proportional, and the variable resistor 25.2
6, the gain G is inversely proportional to the resonant frequency f.

The secondary all-pass circuit is not limited to the ones mentioned above, but bi
Other circuits such as a guad circuit may also be used.

In addition, in the principle diagram of FIG. 1, a bypass path may be provided in parallel with the filter to flatten the frequency characteristics of the portion other than the resonance peak.

As described above, the present invention makes it possible to achieve more diverse frequency characteristics than before by operating the same controller as before by making the changes in the resonance characteristics of a large number of resonant circuits different from each other, thereby eliminating the drawbacks of the conventional example. It is possible to eliminate some unnecessary timbre control.

Moreover, the present invention applies a musical tone signal to one end of an input resistor as a filter, connects the other end to a secondary all-pass circuit, inverts the phase of the output of the secondary all-pass circuit, and passes the above-mentioned signal through a feedback resistor. Using a filter that feeds back to the other end of the input resistor and extracts the output voltage from the other end of the input resistor, the phase characteristics of the secondary all-pass circuit are changed to change the resonant frequency, and the resonant frequency is changed. Since the height of the resonant peak is changed by changing the feedback resistance, the frequency characteristics can be varied over a wide range over the entire audio frequency band using the second-order all-pass circuit, and the Q can also be varied over a wide range, thus greatly simplifying circuit design.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the principle of the present invention, Fig. 2 a, b
is a circuit diagram showing the filter used in Fig. 1, Fig. 3 is its frequency characteristic diagram, Fig. 4 a and b is a circuit diagram showing another P-wave filter used in Fig. 1, and Fig. 5 is its frequency. 6 is a circuit diagram of a filter used in an embodiment of the present invention, and FIG. 7 is a circuit diagram showing an example of an all-pass circuit constituting the filter of FIG. 6. 1...Input terminal, 2...Output terminal, 3, 4...Filter,
5... Adder, 16... Input terminal, 17... Buffer,
21.22...All-pass circuit, 23...Phase inverter, 2
4... Buffer, R4, R5... Feedback resistor, 25, 26
...Machihen resistance.

Claims (1)

[Claims] 1 A plurality of filters having resonance peaks are connected in parallel, an input signal is supplied to each of the filters, and the output signals of each filter are added together and extracted, and each of the vi-wave filters is The resonant frequency of the resonant peaks is configured to be variable independently of each other, and at least one of the level and Q of each resonant peak is configured to change in accordance with a change in the resonant frequency, and the change characteristics thereof. are configured to be different for each filter, and as the filter, a musical tone signal is applied to one end of the input resistor and the other end is connected to a secondary all-pass circuit 7, and the output of the secondary all-pass circuit is The phase of the second-order all-pass circuit is adjusted by using a filter that inverts the phase of the voltage, returns it to the other end of the input resistor via a return resistor, and extracts the output voltage from the other end of the input resistor. An audio control device characterized in that the resonance frequency is changed by changing the characteristics, and the height of the resonance peak is changed by changing the return resistance.