JP2014142437A - Effect addition apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an effect addition apparatus using a vacuum tube eliminating the necessity of a high power supply voltage.SOLUTION: The effect addition apparatus includes an effect addition path, a delay path and a weighted addition part. The effect addition path adds an effect to an input digital acoustic signal and outputs an effect-added digital acoustic signal. The delay path applies delay to the input digital acoustic signal and outputs a delayed digital acoustic signal. The weighted addition part performs weighted addition of the effect-added digital acoustic signal and the delayed digital acoustic signal. The effect addition path includes a low band cutoff filter, a DA converter, a vacuum tube amplifier circuit, and an AD converter. The low band cutoff filter cuts off a signal of a low frequency band. The vacuum tube amplifier circuit inputs a low-band cutoff analog acoustic signal and outputs an effected added analog acoustic signal to which an effect is added by a circuit using a vacuum tube.

Description

  The present invention relates to an effect adding device for deforming a waveform of an acoustic signal.

  2. Description of the Related Art Conventionally, there has been known a technique for adding, as an effect, waveform deformation that occurs when an acoustic signal generated by a musical instrument is amplified by a vacuum tube amplifier circuit. Patent Document 1 is a technique for simulating a vacuum tube amplifier circuit by digital signal processing and adding an effect of the vacuum tube amplifier circuit. Patent Document 2 is a technique for controlling the distortion rate by increasing or decreasing the level of a musical sound applied to a vacuum tube amplifier circuit.

JP-A-6-342287 JP-A-2005-321566

  However, since the technique of Patent Document 1 does not use an actual vacuum tube, it can be processed with a low power supply voltage, but there is a problem that the same effect as a vacuum tube cannot be added. Further, in the technique of Patent Document 2, an acoustic signal to be processed is an analog signal, and a vacuum tube must handle a wide range of amplitudes. Therefore, a power supply voltage applied to the plate of the vacuum tube is around + 200V. There is a problem that such a high power supply voltage is necessary.

  An object of this invention is to provide the effect addition apparatus using the vacuum tube which does not require a high power supply voltage.

  The effect adding device of the present invention changes the waveform of an acoustic signal as an effect on the acoustic signal. This effect addition device has an effect addition path, a delay path, and a weighted addition unit. The effect addition path adds an effect to the input digital sound signal and outputs the effect added digital sound signal. The delay path delays the input digital acoustic signal and outputs the delayed digital acoustic signal. The weighted addition unit weights and adds the effect-added digital sound signal and the delayed digital sound signal. The effect addition path includes a low-frequency cutoff filter, a DA converter, a vacuum tube amplifier circuit, and an AD converter. The low-frequency cutoff filter blocks signals in a low-frequency band. The DA converter converts a digital signal into an analog signal. The vacuum tube amplification circuit inputs the low-frequency cutoff analog acoustic signal, which is the signal after the input digital acoustic signal has been processed by at least the low-frequency cutoff filter and DA converter, and adds effects to the circuit using a vacuum tube. The effect-added analog acoustic signal is output. The AD converter converts the effect-added analog sound signal into a digital signal and outputs the effect-added digital sound signal.

  The low frequency often has a large amplitude, but the effect of the vacuum tube is hardly added to the low frequency sound. According to the effect adding device of the present invention, since the low-frequency cutoff filter is provided, such low-frequency sound can be blocked and the amplitude of the signal input to the vacuum tube amplifier circuit can be reduced. Therefore, the power supply voltage applied to the vacuum tube can be lowered. Moreover, since the input acoustic signal is delayed and weighted with the effect of the vacuum tube, problems such as fading can be avoided.

FIG. 3 is a diagram illustrating a configuration example of an effect adding device according to the first embodiment. The figure which shows the structural example of the effect addition apparatus of Example 1 modification. FIG. 6 is a diagram illustrating a configuration example of an effect adding device according to a second embodiment. The figure which shows the structural example of the effect addition apparatus of Example 2 modification. The figure which shows the structural example of the music synthesizer containing the effect addition apparatus of this invention. The figure which shows the structural example of the effector containing the effect addition apparatus of this invention.

  Hereinafter, embodiments of the present invention will be described in detail. In addition, the same number is attached | subjected to the structure part which has the same function, and duplication description is abbreviate | omitted.

  FIG. 1 shows a configuration example of the effect adding device of the first embodiment. The effect adding device 100 deforms the waveform of the acoustic signal as an effect on the acoustic signal. The input digital acoustic signal to be processed is a digital signal of 48000 samples / second, for example, and corresponds to an analog acoustic signal of about 100 Hz to about 20 kHz. The effect addition apparatus 100 includes an effect addition path 105, a delay path 205, a weighted addition unit 320, and a control unit 410. The effect addition path 105 adds an effect to the input digital sound signal and outputs the effect addition digital sound signal. The delay path 205 delays the input digital acoustic signal and outputs the delayed digital acoustic signal. The weighted addition unit 320 includes an amplifier 160, an amplifier 260, and an adder 310, and adds the effect-added digital audio signal and the delayed digital audio signal with weight. The effect addition path 105 includes an amplifier 110, a low-frequency cutoff filter 120, a DA converter 130, a vacuum tube amplifier circuit 140, and an AD converter 150.

  The amplifier 110 adjusts the amplitude of the input digital acoustic signal. In the case of the configuration shown in FIG. 1, the effect adding device includes three amplifiers. The control unit 410 adjusts the waveform deformation amount (effect depth) due to the effect by adjusting the amplifier 110. The control unit 410 adjusts the balance of effect addition by the weighting of the weighted addition unit 320. The control unit 410 adjusts the volume by adjusting the amplifier 110 and the amplifier 160 and the amplifier 260 of the weighted addition unit 320 as a whole (for example, adjusting the amplification factor ratio to be constant). Note that the amplifier 110 may not be provided when it is not necessary to adjust the deformation amount of the waveform or when the input digital acoustic signal is input with the amplitude adjusted.

  The low-frequency cutoff filter 120 blocks a signal in a low-frequency band by digital signal processing. The acoustic signal often has a large amplitude in the low range, but the effect of the vacuum tube is hardly added to the low range sound. Therefore, the low-frequency cutoff filter 120 blocks, for example, a low frequency band of at least 300 Hz or less. Moreover, the frequency of 400 Hz or more is not cut off. Then, the frequency from 300 Hz to 400 Hz may be appropriately designed in consideration of the frequency characteristics of the acoustic signal to be processed and the characteristics of the vacuum tube. For example, there is a design in which the cutoff frequency band is 350 Hz or less. In this way, since the amplitude of the input signal to the vacuum tube amplifier circuit 140 can be reduced, the dynamic range required for the vacuum tube amplifier circuit 140 can be narrowed and the power supply voltage can be lowered.

  The DA converter 130 converts a digital signal into an analog signal. The vacuum tube amplifier circuit 140 receives as input a low-frequency cutoff analog acoustic signal, which is a signal after the input digital acoustic signal has been processed by at least the low-frequency cutoff filter 120 and the DA converter 130, and is based on a circuit using a vacuum tube. Outputs an effect-added analog audio signal with added effects.

  The AD converter 150 converts the effect-added analog sound signal into a digital signal and outputs the effect-added digital sound signal. The addition of the effect (deformation of the waveform) in the vacuum tube amplifier circuit 140 generates a high frequency component signal. Therefore, it is desirable that the AD converter 150 performs AD conversion after sufficiently removing a signal having a frequency higher than the sampling frequency. Accordingly, it is desirable that the cutoff characteristic is steeper than at least a normal anti-aliasing filter.

  The delay path 205 includes a delay unit 210. The delay time in the delay path 205 may be longer than the sum of the signal conversion time in the DA converter 130 and the signal conversion time in the AD converter 150. Specifically, the delay time may be about 1 to 5 ms, and the signal conversion time in the DA converter 130 and the signal conversion time in the AD converter 150 even if the delay time is not a problem for the musical instrument player. Can be longer than the sum of Moreover, you may provide the structure part which performs a certain signal processing with respect to digital signals, such as the equalizer 220. FIG. Note that when digital signal processing is performed, a delay in the component may be considered as a delay time of the delay path 205.

  According to the effect adding device 100, since the low-frequency cutoff filter is provided, the low-frequency sound can be cut off, and the amplitude of the signal input to the vacuum tube amplifier circuit can be reduced. Therefore, the power supply voltage applied to the vacuum tube can be lowered. Specifically, the power supply voltage for the vacuum tube can be about 5V. Also, since the input acoustic signal is delayed and weighted and added to the effect of the vacuum tube, the effect of the vacuum tube can be added while avoiding problems such as fading and unexpected timbre changes. Therefore, an effect adding device using a vacuum tube that does not require a high power supply voltage can be provided.

[Modification]
FIG. 2 shows a configuration example of an effect adding device according to a modification of the first embodiment. The effect adding device 600 is different from the effect adding device 100 in the arrangement of the low-frequency cutoff filter 620 and the DA converter 630. The rest is the same as the effect adding device 100. Since the effect adding device 600 performs low-frequency cutoff after performing DA conversion first, the low-frequency cutoff filter 620 is an analog filter. Thus, even if the low frequency band is cut off by the analog filter, the same effect as the first embodiment can be obtained. Therefore, the order of DA conversion and low-frequency cutoff may be interchanged.

  FIG. 3 shows a configuration example of the effect adding device of the second embodiment. The effect adding device 500 converts the low-frequency cutoff analog acoustic signal into a signal that has also been processed outside the effect adding device 500, or is processed outside the effect adding device 500, before the vacuum tube amplifier circuit 140. It differs from the effect adding device 100 in that it also includes a switch 510 for selecting whether or not the signal is not used. Other configurations are the same as those of the effect adding device 100. External processing means, for example, processing by an external effector. Since the effect adding device 500 has such a configuration, the effect of an external effector that performs processing on an analog sound signal can also be used. Moreover, the same effect as the effect addition apparatus of Example 1 is acquired. In the case of the effect adding device 500, the delay time in the delay path 205 may be set in consideration of the delay time in the external effector.

[Modification]
FIG. 4 shows a configuration example of the effect adding device of the second embodiment. The effect adding device 700 is different from the effect adding device 500 in the arrangement of the low-frequency cutoff filter 620 and the DA converter 630. The rest is the same as the effect adding device 500. Since the effect adding device 700 performs low-frequency cutoff after performing DA conversion first, the low-frequency cutoff filter 620 is an analog filter. Thus, even if the low frequency band is cut off by the analog filter, the same effect as in the second embodiment can be obtained. Therefore, the order of DA conversion and low-frequency cutoff may be interchanged.

  In this embodiment, an application example of the effect adding device shown in the first and second embodiments will be described. FIG. 5 shows a configuration example of a music synthesizer including the effect adding device of the present invention, and FIG. 6 shows a configuration example of an effector including the effect adding device of the present invention. The music synthesizer 800 includes effect adding apparatuses 100, 500, 600, 700, a control unit 810, a PCM sound source 820, a keyboard 830, a control panel 840, a MIDI interface 850, and a DA converter 860. The control unit 810 controls the PCM sound source 820 and the effect adding devices 100, 500, 600, and 700 based on instructions input from the keyboard 830, the control panel 840, and the MIDI interface 850, and outputs the digital sound signal with the effect added thereto. Generate. The DA converter 860 converts the generated digital sound signal into an analog sound signal and outputs the analog sound signal. In this way, a music synthesizer that can add the effect of a vacuum tube can be configured.

  The effector 900 includes an AD converter 910, an effect adding device 100, 500, 600, 700, and a DA converter 920. For example, an analog sound signal from an electric guitar is input to the effector 900. The AD converter 910 converts an analog sound signal into a digital sound signal. The effect adding devices 100, 500, 600, and 700 deform the waveform using a vacuum tube amplifier. The DA converter 920 converts the output of the effect adding devices 100, 500, 600, and 700 into an analog acoustic signal. In this way, it is possible to produce a sound obtained by amplifying an electric guitar with a vacuum tube amplifier.

100, 500, 600, 700 Effect adding device 105, 505, 605, 705 Effect adding path 110, 160, 260 Amplifier 120, 620 Low-frequency cutoff filter 130, 630, 860, 920 DA converter 140 Vacuum tube amplifier circuit 150, 910 AD converter 205 Delay path 210 Delay unit 220 Equalizer 310 Adder 320 Weighted addition unit 410, 810 Control unit 510 Switch 800 Music synthesizer 820 PCM sound source 830 Keyboard 840 Control panel 850 MIDI interface 900 Effector

Claims (7)

An effect adding device for deforming the waveform of an acoustic signal as an effect on the acoustic signal,
An effect adding path for adding an effect to the input digital sound signal and outputting the effect added digital sound signal;
A delay path for delaying the input digital acoustic signal and outputting the delayed digital acoustic signal;
A weighted adder for weighted addition of the effect-added digital acoustic signal and the delayed digital acoustic signal;
Have
The effect addition route is
A low-frequency cutoff filter that blocks signals in the low-frequency band;
A DA converter for converting a digital signal into an analog signal;
The effect of adding an effect by a circuit using a vacuum tube, with the low-frequency cutoff analog acoustic signal, which is a signal after the processing of at least the low-frequency cutoff filter and the DA converter, being input to the input digital acoustic signal A vacuum tube amplifier circuit for outputting an additional analog acoustic signal;
An effect addition apparatus comprising: an AD converter that converts the effect-added analog sound signal into a digital signal and outputs the effect-added digital sound signal. The effect adding device according to claim 1,
The low-frequency band cut off by the low-frequency cutoff filter includes a frequency band of 300 Hz or less. The effect adding device according to claim 2,
The low-frequency band cut off by the low-frequency cutoff filter does not include a frequency band of 400 Hz or higher. The effect adding device according to any one of claims 1 to 3,
The effect addition route is
An amplifier for adjusting the amplitude of the input digital acoustic signal;
Adjust the amount of waveform deformation due to the effect by adjusting the amplifier,
Adjust the balance of effect addition by weighting of the weighted addition unit,
The effect adding device, wherein the volume is adjusted by overall adjustment of the amplifier and the weighted addition unit. It is an effect addition apparatus in any one of Claim 1 to 4, Comprising:
The effect addition route is
There is also provided a switch for selecting whether the low-frequency cutoff analog acoustic signal is a signal subjected to processing outside the effect adding device or a signal not processed outside the effect adding device. An effect adding device characterized by that. It is an effect addition apparatus in any one of Claim 1 to 5,
The delay time in the delay path is longer than the sum of the signal conversion time in the DA converter and the signal conversion time in the AD converter. The effect adding device according to any one of claims 1 to 6,
The AD converter converts the effect-added analog acoustic signal into a digital signal after removing a signal having a frequency higher than the sampling frequency with a predetermined steep cutoff characteristic.

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