JP4244897B2 - Analog equipment simulator - Google Patents

Description

  The present invention relates to an analog device simulator that simulates the linearity of an analog device and reproduces a warm tone such as a vacuum tube amplifier.

  In the conventional vacuum tube amplifier, a nonlinear distortion peculiar to the vacuum tube is generated in the output acoustic signal. However, due to the generated distortion, a unique taste is added to the acoustic signal. In order to obtain such a vacuum tube amplifier digitally, various effect devices for simulating nonlinear distortion generated in the vacuum tube amplifier have been proposed. For example, as a method of adding nonlinear distortion to an acoustic signal, there are a method of adding the distortion in an analog manner using a nonlinear characteristic of a diode or a hysteresis characteristic of a transformer, and a method of adding nonlinear distortion to an acoustic signal digitally. In addition, the distortion characteristic in the operation region (non-saturation region) among the characteristics of the vacuum tube amplifier can be realized by a square arithmetic circuit, and the saturation characteristic in the saturation region can be realized by conversion using a nonlinear table. In this way, the non-linear table can mimic a delicate characteristic curve well, and the square arithmetic circuit can easily change its characteristic by changing the supplied parameter (patent). Reference 1).

As described above, in a method of approximating nonlinear distortion to a polynomial such as an n-order function or a Fourier series or converting according to a conversion table, necessary types of nonlinear distortion data must be created in advance by default. In the method using the table, it is difficult for the user to freely correct the nonlinear characteristic.
Therefore, a reference signal is applied to an analog device such as a vacuum tube amplifier or an analog tape deck, and a measurement signal obtained by nonlinear conversion of the reference signal is obtained from the vacuum tube amplifier or the analog tape deck, and the relationship between the measurement signal and the reference signal is obtained. Based on this, it is proposed to simulate the tube amplifier and analog tape deck by calculating the nonlinear control data for simulating the tube amplifier and analog tape deck and setting the calculated effect parameters in the effect applying device. (See Patent Document 2).
JP-A-6-342287 JP 2004-109279 A

In analog equipment, the amount of harmonic distortion that occurs varies depending on the frequency of the input signal. However, the conventional method of simulating nonlinearity does not sufficiently simulate the timbre characteristics of analog equipment. there were. This is because the amount of harmonic distortion generated for each of the second, third,... N-th harmonic orders differs depending on the frequency, and the amount of generated harmonic distortion for each harmonic order depends on the tone of the analog device. This is because it is considered to be an important factor that determines the above. However, the method of simulating using nonlinear characteristics has a problem that the amount of harmonic distortion generated cannot be changed according to the frequency for each harmonic order.
Accordingly, an object of the present invention is to provide a simulator for an analog device that can change the amount of harmonic distortion generated according to the frequency for each harmonic order.

In order to achieve the above object, an analog device simulator according to the present invention includes a fundamental tone generating means in which data for obtaining a fundamental frequency characteristic output from an analog device to be simulated is set, and an output from the analog device to be simulated. It is the most important feature that the data obtained by the frequency characteristic of each harmonic order of the harmonic distortion and a harmonic distortion generating means is set to be.

According to the present invention, the fundamental sound generating means in which data capable of obtaining the frequency characteristic of the fundamental sound output from the analog device to be simulated is set, and the harmonic distortion is output for each harmonic order of the harmonic distortion output from the analog device to be simulated. With the harmonic distortion generation means set with data that can obtain frequency characteristics, the amount of harmonic distortion can be changed according to the frequency for each harmonic order, and the tone of analog equipment The characteristics can be fully simulated. Thus, since the amount of harmonic distortion generated is simulated for each order of harmonics, the timbre characteristics of analog equipment can be realistically simulated.

For the purpose of providing a simulator for analog equipment that can change the amount of harmonic distortion generated for each harmonic order according to the frequency, there is data that can obtain the frequency characteristics of the fundamental sound output from the analog equipment to be simulated. Realized by having set fundamental tone generating means and harmonic distortion generating means set with data to obtain frequency characteristics for each harmonic order of harmonic distortion output from analog device to be simulated did.

FIG. 1 is a block diagram showing a configuration of a simulator for an analog device according to the first embodiment of the present invention. The analog device simulator 1 shown in FIG. 1 can simulate an analog device such as a vacuum tube amplifier or an analog tape deck.
An input signal IN input to the simulator 1 of the analog device shown in FIG. 1 is a signal obtained by A / D converting an analog signal supplied from a microphone or guitar pickup, or a digital signal stored in a recording medium such as a hard disk or an optical disk. It is a digital signal such as a reproduction signal obtained by reproducing an acoustic signal. The input signal IN, which is a digital signal, is supplied to a first characteristic approximation filter (CAF) 13 that generates a fundamental signal, and also serves as a first input and a second input of the first multiplier 10. In the first multiplier 10, since the input signals IN are multiplied, the second harmonic signal of the input signal IN is output. The output of the first multiplier 10 is input to a low-frequency cutoff filter (LCF) 11 to remove unnecessary low-frequency components, and a second-order harmonic signal having a higher harmonic order of the input signal IN is output. The second harmonic signal of the input signal IN is supplied to a second characteristic approximation filter (CAF) 14 that generates a second harmonic distortion signal. Further, the output of the LCF 11 becomes one input of the second multiplier 12, and the input signal becomes the other input of the second multiplier 12. As a result, the second multiplier 12 multiplies the input signal IN and the second-order harmonic signal, and outputs a third-order higher harmonic signal. This third-order harmonic signal is supplied to a third characteristic approximation filter (CAF) 15 that generates a third-order harmonic distortion signal.

  The first characteristic approximation filter 13 is set with data that can generate from the input signal IN a fundamental signal having the same frequency characteristics as the fundamental signal output from the analog device to be simulated. Similarly, the second characteristic approximation filter 14 is data that can generate a second-order distortion signal having the same frequency characteristic as the second-order distortion signal output from the analog device to be simulated from the second-order harmonic signal. Is set, and the third characteristic approximation filter 15 can generate a third-order distortion signal having the same frequency characteristic as the third-order distortion signal output from the analog device to be simulated from the third-order harmonic signal. Data is set. The first characteristic approximation filter 13 to the third characteristic approximation filter 15 can be constituted by digital filters such as an FIR filter (Finite Impulse Response Filter) and an IIR (Infinite Impulse Response Filter) filter. The set data is a filter coefficient. The first characteristic approximation filter 13 to the third characteristic approximation filter 15 divide the audio frequency band into a plurality of parts by a plurality of filters having a fixed center frequency, and adjust the enhancement / attenuation of the pass level for each band. The graphic equalizer can be configured, and the data set in this case is level information for each frequency band. Alternatively, the first characteristic approximation filter 13 to the third characteristic approximation filter 15 may be configured by a parametric equalizer in which a plurality of filters each capable of independently adjusting the center frequency, selectivity (Q), and level information are connected in series. The parameters that can be set in this case are the center frequency, Q, and level information for each filter. Further, the first characteristic approximation filter 13 to the third characteristic approximation filter 15 can be constituted by a signal processing means comprising a fast Fourier transform (FFT) -characteristic multiply-inverse fast Fourier transform (IFFT), and this The data set in this case is amplitude coefficient data to be multiplied to each spectrum as the FFT result.

  As a result, the first characteristic approximation filter 13 outputs a fundamental signal having a generation amount corresponding to the same frequency as the fundamental signal output from the analog device to be simulated, and the second characteristic approximation filter 14 performs simulation. A second-order distortion signal having an amount corresponding to the same frequency as the second-order distortion signal output from the analog device desired to be output is output, and the third characteristic approximation filter 15 outputs the third-order distortion output from the analog device desired to be simulated. A generated third-order distortion signal corresponding to the same frequency as the signal is output. In the first adder 16, the fundamental signal output from the first characteristic approximation filter 13 and the secondary distortion signal output from the second characteristic approximation filter 14 are added, and in the second adder 17 The third-order distortion signal output from the third characteristic approximation filter 15 and the addition signal output from the first adder 16 are added. As a result, a synthesized signal of the fundamental signal, the second-order distortion signal, and the third-order distortion signal is output from the second adder 17 and corresponds to the same frequency as the output signal signal output from the analog device to be simulated. Output signal is output. This output signal is D / A converted, and the converted analog signal is amplified and emitted from the speaker. Alternatively, the digital signal is recorded on a recording medium such as a hard disk.

In this case, the harmonic distortion generating means is configured by a characteristic approximation filter in which data of the generation amount of each harmonic distortion corresponding to the frequency in the analog device to be simulated is set, and thus harmonic distortion is generated. Generation amount can be changed for each harmonic order, and the timbre characteristic of the analog device can be sufficiently simulated. Thus, since the amount of harmonic distortion generated is simulated for each harmonic order, the timbre characteristics of analog equipment can be realistically simulated.
As described above, since the analog device is simulated according to the data set in the first characteristic approximation filter 13 to the third characteristic approximation filter 15, a plurality of analog devices for simulating different analog devices. Each data set is stored in a rewritable nonvolatile memory 18 such as a flash memory. When the user selects a desired analog device by the selection unit 19, the corresponding data set is read and the data set read to the first characteristic approximation filter 13 to the third characteristic approximation filter 15. Set each data. As a result, various analog devices can be simulated by the simulator 1.

Next, a method for generating data to be set in the first characteristic approximation filter 13 to the third characteristic approximation filter 15 will be described below. FIG. 3 is a block diagram showing the overall configuration of the measurement apparatus that generates the data.
In FIG. 3, a system under test 30 is an analog device to be simulated, and is a vacuum tube amplifier, an analog tape deck, or the like. A chirp signal is supplied to the system under measurement 30. The chirp signal is a sine wave signal whose amplitude is substantially constant regardless of the frequency with which the frequency is swept with time, and the sweep width is, for example, 0 to 20 kHz. FIG. 4 shows the waveform of the chirp signal. The horizontal axis represents the sample number of the chirp signal waveform, the vertical axis represents the amplitude, and the waveform is a sine wave. FIG. 5 shows the frequency characteristics of the chirp signal level. The horizontal axis represents the logarithmic frequency, and the vertical axis represents the level represented by dB. As shown in these figures, the chirp signal is swept at a frequency of 0 to 20 kHz, for example, and has a constant level (for example, 35 dB) in a frequency band from 0 to 20 kHz. It is not included and consists only of fundamental signals.

  Such a chirp signal is supplied to the system under test 30 and its output is supplied to the speaker 31. The sound of the chirp signal emitted from the speaker 31 is collected by the microphone 32. In this way, the output of the system under test 30 is emitted from the speaker 31 and collected by the microphone 32, for example, in order to make sound including the speaker in a guitar amplifier. The waveform of the chirp signal collected by the microphone 32 is shown in FIG. The collected chirp signal is affected by the nonlinear characteristics of the system under test 30 and is converted into a digital signal having a predetermined sampling frequency by an analog / digital converter (A / D) 33. The collected chirp signal converted into a digital signal is supplied to a computer 34 for signal analysis of nonlinear characteristics. The computer 34 performs signal analysis processing on the collected chirp signal, thereby generating a data set to be set in each of the first characteristic approximation filter 13 to the third characteristic approximation filter 15. This data set is a data set for simulating the nonlinear characteristic of the system under test 30. Hereinafter, an example of the nonlinear characteristic of the system under test 30 will be described.

  The chirp signal picked up by the microphone 32 becomes a chirp signal reflecting the non-linear characteristic of the system under test 30, and when the chirp signal collected as shown in FIG. 6 is subjected to FFT processing in order to clearly show the non-linear characteristic. The spectrum of is shown in FIG. In FIG. 7, the horizontal axis represents time (ms) and the vertical axis represents frequency (Hz). Since the frequency of the chirp signal is swept with time, the spectrum of the fundamental tone of the chirp signal appears on a straight line having a predetermined slope. Further, when the second-order distortion or the third-order distortion occurs due to the non-linearity of the system under measurement 30, the spectra of the second-order distortion and the third-order distortion appear on straight lines having different predetermined inclinations. FIG. 7 shows a straight line in which the spectrum of the fundamental tone of the collected chirp signal shown in FIG. 6 and the spectrum of the second-order distortion and the third-order distortion appear. In this case, since the spectrum of the secondary distortion is a harmonic that is twice the fundamental spectrum, the slope of the spectrum of the secondary distortion is twice the slope of the fundamental spectrum. The slope of the distortion spectrum is three times the slope of the fundamental spectrum. Referring to FIG. 7, it is shown that in addition to the fundamental tone spectrum, the second-order distortion and third-order distortion spectra appear on the straight line, and the measured system 30 has nonlinear characteristics and has second-order distortion. It can be seen that the third-order distortion occurs.

  In order to know the frequency characteristics of the generation amount of the second order distortion and the third order distortion, which are harmonics of the fundamental tone, the fundamental spectrum, the second order distortion, and the third order when the chirp signal shown in FIG. 7 is subjected to FFT processing. Obtain level information for each distortion spectrum. FIG. 8 shows the frequency characteristics of the fundamental tone, second-order distortion, and third-order distortion generated in this way. Referring to FIG. 8, the fundamental tone has a level of approximately 35 dB over a band of 20 Hz to 20 kHz, but has a frequency characteristic in which the level is slightly attenuated in a low band of several tens Hz or less and a high band near 20 kHz. The secondary distortion has a level that is attenuated by about 20 dB from the fundamental tone in a low band of several hundred Hz or less, and has a frequency characteristic that shows a tendency to attenuate gradually as the frequency increases. The third-order distortion has a level that is attenuated by about 20 dB from the fundamental tone in a low band of about 100 Hz or less, and has a frequency characteristic that repeats further attenuation and increment as the frequency increases.

  A data set capable of obtaining the frequency characteristics of the fundamental tone, the second-order distortion, and the third-order distortion as shown in FIG. 8 is generated by the computer 34 and set in the first characteristic approximation filter 13 to the third characteristic approximation filter 15. As a result, the simulator 1 can simulate the system under test 30. When the first characteristic approximation filter 13 to the third characteristic approximation filter 15 are constituted by digital filters such as an FIR filter or an IIR filter, each data of the data set generated by the computer 34 is a filter coefficient. . In addition, when the first characteristic approximation filter 13 to the third characteristic approximation filter 15 are configured by a parametric equalizer, each data of the data set generated by the computer 34 is the center frequency of each filter constituting the parametric equalizer. , Selectivity (Q), and level information data. When the graphic equalizer is used, the data is level information data for each divided frequency band. Furthermore, the first characteristic approximation filter 13 to the third characteristic approximation filter 15 can be constituted by signal processing means comprising fast Fourier transform (FFT) -characteristic multiplication-inverse Fourier transform (IFFT). The data set to is amplitude coefficient data to be multiplied to each spectrum as the FFT result.

  Note that, with the configuration shown in FIG. 3, various analog devices such as vacuum tube amplifiers and analog tape decks are used as the measured system 30, and data sets for different measured systems 30 obtained by measuring the characteristics are stored in the memory 18. Has been. In this case, when the user selects a desired analog device by the selection unit 19, the corresponding data set is read from the memory 18, and each data of the data set is changed from the first characteristic approximation filter 13 to the third characteristic approximation. The filter 15 is set. As a result, various analog devices can be simulated by the simulator 1.

Next, FIG. 2 is a block diagram showing the configuration of the simulator of the analog device according to the second embodiment of the present invention. The analog device simulator 2 shown in FIG. 2 can also simulate an analog device such as a vacuum tube amplifier or an analog tape deck.
The analog device simulator 2 of the second embodiment shown in FIG. 2 includes a first filter (F1) 20, a second filter (F2) 21, and a third filter (F3) 22, 1 is different from the analog device simulator 1 of the first embodiment shown in FIG. 1 in the configuration in which the first gain control unit 23, the second gain control unit 24, and the third gain control unit 25 are provided. Only the different configuration will be described below.

  In the simulator 1 of the analog device of the first embodiment shown in FIG. 1, since digital signals are processed, aliasing may occur in the generation processing of the second order distortion and the third order distortion depending on the sampling frequency. Therefore, the first filter (F1) 20, the second filter (F2) 21, and the third filter (F3) 22 are provided to prevent the occurrence of alias. The first filter (F1) 20 is inserted before the first multiplier 10 and limits the frequency band of the input signal IN to ½. For example, when the input signal IN has a frequency band of 0 to 20 kHz, the first filter (F1) 20 limits the band to 0 to 10 kHz. As a result, no alias is generated in the configuration that handles the second-order harmonics after the first multiplier 10. The second filter (F2) 21 is inserted between the LCF 11 and the second multiplier 12, and limits the frequency band in the input signal IN to 2/3. Further, the third filter (F3) 22 is inserted between the first filter (F1) 20 and the second multiplier 12, and limits the frequency band in the input signal IN to 1/3. . As a result, no alias is generated in the configuration subsequent to the second multiplier 12. If the frequency band of the input signal IN is limited to 1/3 by the first filter (F1) 20, the second filter (F2) 21 and the third filter (F3) 22 may be omitted. An alias can be prevented from occurring.

  The first gain control unit 23 is supplied with the output of the first characteristic approximation filter 13 and controls the level of the fundamental tone. The second gain control unit 24 is supplied with the output of the second characteristic approximation filter 14 to control the level of second-order distortion, and the third gain control unit 25 is provided with the third characteristic approximation filter 15. Are supplied to control the third order distortion level. By controlling the first gain control unit 23, the second gain control unit 24, and the third gain control unit 25, the sound output from the second adder 17 can be generated. Further, the control data set in the first gain control unit 23 to the third gain control unit 25 is included in the data set for each analog device stored in the memory 18. The value of this control data is set in advance by the user. When the selection unit 19 selects a desired analog device, the corresponding data set is read, and the first characteristic approximation filter 13 to the third characteristic approximation filter 15 and the first gain control unit are read out. Each data of the read data set may be set in the 23rd to the third gain control unit 25. In this way, it is possible to output a sound created according to the selected analog device.

In the above description, the analog device is simulated by the fundamental tone, the second-order distortion, and the third-order distortion. However, the analog device may be simulated by adding higher-order higher-order distortion. In this case, harmonics up to the required high-order distortion are generated from the input signal and supplied to the corresponding characteristic approximation filters.
In the above description, the sound output from the speaker 31 driven by the output of the system under test 30 is picked up and analyzed by the microphone 32. However, the analog signal output from the system under measurement 30 may be A / D converted to analyze only the characteristics of the system under measurement 30. Further, the characteristics of the system under test 30 can be subtracted from the characteristics including the speaker 31 to obtain the characteristics of the speaker 31.

Furthermore, the frequency bands of the second and third distortions are set to the same frequency band as that of the fundamental sound. However, the present invention is not limited to this, and the frequency band of the second distortion is set to twice the frequency band of the fundamental sound. A data set may be generated by performing signal analysis with the band being three times the frequency band of the fundamental tone.
In the above description, the simulator according to the present invention is a simulator that simulates an analog device. However, the simulation target of the simulator according to the present invention is not limited to a vacuum tube amplifier or a transistor amplifier, and may be a compressor. It may be an effect circuit such as a limiter or distortion, or a recording / reproducing circuit such as a tape recorder. Furthermore, not only analog circuits but also non-linearities from analog inputs to analog outputs of digital circuits can be simulated.

The simulator of the present invention can be realized by using hardware such as a DSP, but can also be realized by a computer in which a simulator program is installed. In this case, the computer includes harmonic generation means for generating harmonics of the input signal for each harmonic order, fundamental sound generation means in which data for obtaining frequency characteristics of the fundamental sound output from the analog device to be simulated is set, Harmonic distortion generating means in which data for obtaining frequency characteristics for each harmonic order of the harmonic distortion output from the analog device to be simulated is set, the fundamental signal output from the fundamental generating means, and the harmonic distortion It functions as a synthesizing means for synthesizing and outputting the harmonic distortion signal for each harmonic order outputted from the generating means.

It is a block diagram which shows the structure of the simulator of the analog apparatus of the 1st Example of this invention. It is a block diagram which shows the structure of the simulator of the analog apparatus of the 2nd Example of this invention. It is a block diagram which shows the whole structure of the measuring device which acquires the data set to the 1st characteristic approximation filter thru | or 3rd characteristic approximation filter in the simulator of this invention. It is a figure which shows the waveform of the chirp signal supplied to the measuring apparatus shown in FIG. It is a figure which shows the frequency characteristic of the level of the chirp signal supplied to the measuring apparatus shown in FIG. It is a figure which shows the waveform of the chirp signal collected with the microphone in the measuring apparatus shown in FIG. It is a figure which shows the spectrum at the time of performing a FFT process to the chirp signal collected with the microphone in the measuring device shown in FIG. It is a figure which shows the frequency characteristic of the level of a fundamental tone component, a 2nd-order distortion component, and a 3rd-order distortion component which were obtained from the chirp signal collected with the microphone in the measuring device shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Simulator, 2 Simulator, 10 1st multiplier, 11 Low frequency cutoff filter, 12 2nd multiplier, 13 1st characteristic approximation filter, 14 2nd characteristic approximation filter, 15 3rd characteristic approximation filter, 16 first adder, 17 second adder, 18 memory, 19 selection unit, 20 first filter, 21 second filter, 22 third filter, 23 first gain control unit, 24 second Gain control unit, 25 third gain control unit, 30 system to be measured, 31 speaker, 32 microphone, 33 analog / digital converter, 34 computer

Claims (7)

Harmonic generation means for generating harmonics of the input signal for each harmonic order;
Fundamental sound generating means in which data that can obtain the frequency characteristics of the fundamental sound output from the analog device to be simulated is set;
Harmonic distortion generating means in which data that can obtain frequency characteristics for each harmonic order of the harmonic distortion output from the analog device to be simulated is set;
A synthesis unit that synthesizes and outputs a fundamental signal output from the fundamental generation unit and a harmonic distortion signal for each harmonic order output from the harmonic distortion generation unit;
The input signal is input to the fundamental tone generating means, and each harmonic of each harmonic order from the harmonic generating means is input to the harmonic distortion generating means, and the analog device is simulated from the synthesizing means. The analog device simulator is characterized in that the output signal is output. 2. The analog equipment simulator according to claim 1, wherein said fundamental tone generating means is composed of a characteristic approximation filter, and said harmonic distortion generating means includes a characteristic approximation filter for each harmonic order.   Each data set in each of the fundamental tone generation means and the harmonic distortion generation means has frequency characteristics for each harmonic order of the fundamental tone signal and the harmonic distortion signal obtained by inputting a chirp signal to the analog device. 3. The simulator for an analog device according to claim 1, wherein each data is based on the data.   A data set for each different analog device composed of each data set in each of the fundamental tone generation means and the harmonic distortion generation means is stored in a memory, and when selecting an analog device to be simulated by the selection means, A data set corresponding to the selected analog device is read out, and each data of the read data set is set in each of the fundamental tone generation means and the harmonic distortion generation means, thereby selecting the selected analog 4. The analog device simulator according to claim 1, wherein the device is simulated. The characteristic approximating filter of the fundamental tone generating means and the characteristic approximating filter for each harmonic order of the harmonic distortion generating means are constituted by digital filters, and the data for obtaining the frequency characteristics of the fundamental tone is obtained by expressing the frequency characteristics of the fundamental tone. It is a filter coefficient for realizing, and the data for obtaining the frequency characteristic for each harmonic order of the harmonic distortion is a filter coefficient for realizing the frequency characteristic for each harmonic order of the harmonic distortion. The analog device simulator according to claim 2, wherein the simulator is an analog device simulator. The characteristic approximation filter of the fundamental tone generating means and the characteristic approximation filter for each harmonic order of the harmonic distortion generating means are configured by a parametric equalizer, and the data for obtaining the frequency characteristics of the fundamental tone is obtained by expressing the frequency characteristics of the fundamental tone. The center frequency, selectivity (Q), and level information to realize, and the data that can obtain the frequency characteristics for each harmonic order of the harmonic distortion realize the frequency characteristics for each harmonic order of the harmonic distortion. The simulator of an analog device according to claim 2, wherein the information includes a center frequency, selectivity (Q), and level information. The characteristic approximation filter of the fundamental tone generating means and the characteristic approximation filter for each harmonic order of the harmonic distortion generating means are configured by a graphic equalizer, and the data for obtaining the frequency characteristics of the fundamental tone is obtained by expressing the frequency characteristics of the fundamental tone. The level information for each frequency band to be realized, and the data for obtaining the frequency characteristic for each harmonic order of the harmonic distortion is the frequency band for realizing the frequency characteristic for each harmonic order of the harmonic distortion. The analog device simulator according to claim 2, wherein the level information is for each level.