Impedance conversion device and signal processing device

Abstract

To provide an impedance conversion device and a signal processing device that connect a guitar amplifier 40 to an electric musical instrument such as an electric guitar to emit sound, and converts the impedance of an analog signal An1 output from the bass guitar and supplies the signal to a digital conversion device.SOLUTION: In a signal processing device 10, an impedance conversion device 12 includes an input terminal In1 to which an analog signal An1 output from an electric musical instrument such as an electric guitar 30 is input, a branching portion 122 that branches the analog signal An1 into analog signals An2 and An3, an output terminal Out1 to which the analog signal An2 is output, an impedance conversion circuit 124 that converts the impedance of the analog signal An3, and an output terminal Out2 to which the impedance-converted analog signal An3 is output, and the input impedance of the impedance circuit is approximately 1 GΩ or more.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present disclosure relates to an impedance transforming device and a signal processing device. [Background technology]

[0002] Analog signals generated by playing electric instruments such as bass guitars and electric guitars are output as musical tones through guitar amplifiers. In recent years, there have been cases where people want to edit musical tones after playing. For these reasons, firstly, the analog signals output from electric instruments are first recorded digitally. Secondly, the recorded musical tone signals are edited on a computer using the functions of a DAW (Digital Audio Workstation), and then output through a guitar amplifier in a studio or other location for confirmation.

[0003] When using this method, it is important to keep in mind the following: the analog signal output from an electric musical instrument is generally high impedance, whereas the input to the device used for digital conversion is low impedance. For this reason, if an electric musical instrument is directly connected to a digital conversion device, impedance mismatch can result in noise being superimposed or the signal waveform being distorted.

[0004] Therefore, a method is adopted in which the impedance of an analog signal output from an electric musical instrument is converted by a preamplifier circuit or the like, and the impedance-converted analog signal is supplied to a digital conversion device. For example, a technology described in Patent Document 1 is known as an example of such a preamplifier circuit. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2018-180478 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the technology described in Patent Document 1 does not allow a guitar amplifier to be connected to an electric musical instrument and sound to be emitted through the guitar amplifier, nor does it allow the impedance of the analog signal output from the electric musical instrument to be converted and supplied to a digital conversion device. [Means for solving the problem]

[0007] An impedance conversion device according to one embodiment of the present disclosure includes a first input terminal to which a first analog signal output from an electric musical instrument is input, a branching section to branch the first analog signal into a second analog signal and a third analog signal, a first output terminal to which the second analog signal is output, an impedance conversion circuit to convert the impedance of the third analog signal, and a second output terminal to which the impedance-converted analog signal is output, wherein the input impedance of the impedance conversion circuit is approximately 1 GΩ or more. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a signal processing device including an impedance conversion device according to an embodiment. [Diagram 2] FIG. 2 is a diagram illustrating an example of an impedance conversion circuit. [Diagram 3] 1A and 1B are diagrams for explaining correction of AD conversion characteristics of a signal processing device. [Figure 4] 1A and 1B are diagrams for explaining correction of the DA conversion characteristic of a signal processing device. [Diagram 5] FIG. 13 is a diagram illustrating correction of phase characteristics with respect to frequency. [Figure 6] FIG. 13 is a diagram showing correction of amplitude characteristics with respect to frequency. [Figure 7] FIG. 2 is a diagram illustrating an example of connections of signal processing devices. [Figure 8] FIG. 2 is a diagram illustrating an example of connections of signal processing devices. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] An impedance converting device according to an embodiment of the present disclosure will now be described with reference to the drawings. It should be noted that the embodiments described below are preferred examples and therefore include various technically preferable limitations. However, the scope of the present invention is not limited to these embodiments unless otherwise specified in the following description to the effect that the present invention is limited to these embodiments.

[0010] FIG. 1 is a block diagram showing a configuration of a signal processing device 10 including an impedance conversion device 12 according to an embodiment. In addition to the impedance conversion device 12, the signal processing device 10 includes audio I / O (Input / Output) 14, 16 and a reamplifier 18. In the drawing, impedance is abbreviated to "Z" for space reasons.

[0011] The impedance conversion device 12 has an input terminal In1, outputs Out1 and Out2, a branch portion 122, and an impedance conversion circuit .

[0012] The branching unit 122 branches a high-impedance analog signal An1 supplied to an input terminal In1 into analog signals An2 and An3. The analog signal An1 is a signal output from an electric musical instrument that converts the vibration of a sounding body into an electric signal. The impedance of the analog signal An1 is, for example, about 200 kΩ to 500 kΩ.

[0013] Of the branched analog signals An2 and An3, the analog signal An2 is output from an output terminal Out1, and the analog signal An3 is supplied to an impedance conversion circuit 124. The impedance conversion circuit 124 is a circuit that converts the high impedance analog signal An3 to a low impedance lower than the impedance of the analog signal An1, and an example of the configuration will be described later. The analog signal An3 converted to the low impedance is output from the output terminal Out2.

[0014] The audio I / O 14 is a device that converts the analog signal An3 converted to a low impedance into a digital signal. Specifically, the audio I / O 14 includes a low pass filter (LPF) 142, an analog to digital converter (ADC) 144, and a finite impulse response (FIR) filter 146.

[0015] The LPF 142 is an analog filter that cuts low frequency components of the analog signal An3 that has been converted to a low impedance. In detail, the LPF 142 cuts low frequency components of the analog signal An3 before digital conversion in order to prevent DC components from being mixed into the analog signal An3. The ADC 144 converts the analog signal An3, from which the low frequency components have been cut by the LPF 142, into a digital signal. The FIR filter 146 is a digital filter that imparts characteristics, described later, to the digital signal output from the ADC 144. Information such as coefficients that define the characteristics imparted by the FIR filter 146 is stored in a memory device M1 built into the FIR filter 146 by an acquisition unit, described later. In other words, the characteristics imparted by the FIR filter 146 are defined by the information stored in the memory device M1. For the sake of convenience, the digital signal output from the FIR filter 146 is denoted as Dg1. The characteristic given by the FIR filter 146 is an example of a "first characteristic."

[0016] The audio I / O 16 is a device that converts a digital signal into an analog signal. Specifically, the audio I / O 16 includes an FIR filter 162, a digital to analog converter (DAC) 164, and an LPF 166.

[0017] The FIR filter 162 is a digital filter that imparts characteristics, which will be described later, to the digital signal Dg1 input to the input terminal In2. Information such as coefficients that define the characteristics imparted by the FIR filter 162 is stored in a memory device M2 built into the FIR filter 162 by an acquisition unit, which will be described later. In other words, the characteristics imparted by the FIR filter 162 are defined by the information stored in the memory device M2. The characteristic given by the FIR filter 162 is an example of the "second characteristic."

[0018] The DAC 164 converts the digital signal output from the FIR filter 162 into an analog signal. The LPF 166 is an analog filter that smoothes the analog or digital signal output from the DAC 164 . For the sake of convenience, the analog signal output from the LPF 166 is denoted as An4.

[0019] The re-amplifier 18 converts the low-impedance analog signal An4 output by the LPF 166 to a high-impedance signal and outputs it. The analog signal converted into impedance is output from the output terminal Out3. The re-amplifier 18 is a device for inputting the low-impedance analog signal An4 to a guitar amplifier, as described below. For the sake of convenience, the analog signal output from the output terminal Out3 is denoted as An5.

[0020] Analog signal An1 is an example of a "first analog signal," analog signal An2 is an example of a "second analog signal," analog signal An3 is an example of a "third analog signal," and analog signal An4 is an example of a "fourth analog signal." The input terminal In1 is an example of a "first input terminal", the input terminal In2 is an example of a "second input terminal", the output terminal Out1 is an example of a "first output terminal", the output terminal Out2 is an example of a "second output terminal", and the output terminal Out3 is an example of a "third output terminal". The audio I / O 14 is an example of a "first input / output device," and the audio I / O 16 is an example of a "second input / output device." The ADC 144 is an example of an "A / D conversion section," and the DAC 164 is an example of a "D / A conversion section." The reamp 18 is an example of a "reamp section." The FIR filter 146 is an example of a "first characteristic imparting section," and the FIR filter 162 is an example of a "second characteristic imparting section."

[0021] FIG. 2 is a circuit diagram showing an example of the impedance conversion circuit 124 in the impedance conversion device 12. As shown in FIG. In the impedance conversion circuit 124, the analog signal An3 branched by the branching portion 122 is supplied to an input terminal In3. Of the analog signal An3, only the AC component is supplied to the input section N1. The input section N1 has a transistor Tr1 that inputs the AC component of the analog signal An3 to its gate, and a resistive element R1 that guides the AC component of the analog signal An3 to the midpoint potential of the power supply. The transistor Tr1 is, for example, an N-channel JFET (Junction Field Effect Transistor). A power supply (high level) is applied to the drain of the transistor Tr1, and a signal appearing at the source of the transistor Tr1 is amplified and output from the output terminal Out2. In this embodiment, the resistance value of the resistor element R1 is 1 GΩ. Therefore, in the impedance conversion circuit 124, the DC impedance at the input terminal In3 becomes 1 GΩ.

[0022] When analog signal An1 branches into An2 and An3 in branching section 122 in the previous stage, the DC impedance of input terminal In3 branched to one side is very high at 1 GΩ. Therefore, the impedance of analog signal An2 branched to the other side does not change from the impedance of analog signal An1, and is output from output terminal Out1 with almost the same impedance. An analog signal An3 branched off from the analog signal An1 and supplied to an input terminal In3 is converted to low impedance by the impedance conversion circuit 124 and output from an output terminal Out2.

[0023] FIG. 3 is a diagram showing a configuration for determining the characteristics to be applied by the FIR filter 146. As shown in FIG. The frequency characteristic of the LPF 142, which is an analog filter, is ideally flat, but in reality, it is not flat. In addition, when the ADC 144 processes the analog signal before conversion, the analog signal may change depending on the frequency. On the other hand, it is preferable that the digital signal Dg1 output from the audio I / O 14 is a signal obtained by faithfully digitizing the analog signal An1. For this reason, in this embodiment, the frequency characteristics that change when the analog signal from the output terminal Out2 is processed by the LPF 142 and the ADC 144 are subsequently cancelled by the FIR filter 146 and output as a digital signal Dg1.

[0024] In this embodiment, examples of frequency characteristics include frequency-phase characteristics, which indicate how the phase changes with respect to frequency, and frequency-amplitude characteristics, which indicate how the amplitude changes with respect to frequency. When determining the characteristics of the FIR filter 146, the input terminal of the LPF 142 is disconnected from the output terminal Out2 of the impedance conversion device 12. The output terminal of the ADC 144 is disconnected from the input terminal of the FIR filter 146.

[0025] The acquisition unit 148 obtains the frequency characteristics in the path from the LPF 142 to the ADC 146, and stores information that defines the inverse characteristics of the obtained frequency characteristics in the storage device M1 of the FIR filter 146.

[0026] In detail, the acquiring unit 148 supplies an analog test signal At 1 to the input terminal of the LPF 142 , and receives a digital signal Dm 1 from the output terminal of the ADC 144 . The test signal At1 is, for example, a signal obtained by converting a digital source signal whose frequency is swept across the audible band (20 Hz to 20 kHz) and whose amplitude is uniform, into an analog signal. When the test signal At1 is filtered by the LPF 142 and converted into a digital signal Dm1 by the ADC 146, the digital signal Dm1 becomes a signal in which the frequency characteristics of the LPF 142 and the ADC 144 are imparted to the test signal At1. For this reason, the acquiring unit 148 compares the digital signal Dm1 with the original signal of the test signal At1 to obtain the frequency phase characteristic and the frequency amplitude characteristic of the digital signal Dm1 with respect to the original signal. The acquiring unit 148 stores information that defines the inverse characteristics of the obtained frequency phase characteristic and frequency amplitude characteristic in the memory device M1 of the FIR filter 146. This causes the FIR filter 146 to have frequency characteristics defined by the stored information.

[0027] FIG. 5 is a diagram illustrating an example of correction of the frequency phase characteristic in the FIR filter 146. In FIG. In the figure, "before correction" refers to the phase characteristic of the digital signal Dm1 with respect to the original signal of the test signal At1 when the test signal At1 passes through the LPF 142 and is converted to the digital signal Dm1 by the ADC 144, and the inverse characteristic is the characteristic obtained by inverting the phase characteristic with respect to the characteristic at 0 degrees as a reference. "after correction" refers to the frequency phase characteristic when the inverse characteristic is given to the frequency phase characteristic before correction. As shown in the figure, after correction, the frequency phase characteristic becomes almost flat in the audible band.

[0028] FIG. 6 is a diagram illustrating an example of correction of the frequency amplitude characteristic in the FIR filter 146. In FIG. In the figure, "before correction" refers to the amplitude characteristic of the digital signal Dm1 with respect to the original signal of the test signal At1 when the test signal At1 passes through the LPF 142 and is converted to the digital signal Dm1 by the ADC 144, and the inverse characteristic is the characteristic obtained by inverting the amplitude characteristic with respect to the characteristic at 0 db as a reference. "after correction" refers to the frequency amplitude characteristic when the inverse characteristic is applied to the frequency amplitude characteristic before correction. As shown in the figure, after correction, the amplitude characteristics become almost flat in the audible frequency range.

[0029] FIG. 4 is a diagram showing a configuration for determining the characteristics to be applied by the FIR filter 162. As shown in FIG. In the DAC 164, when processing the converted analog signal, the analog signal may change depending on the frequency. The frequency characteristics of the LPF 166, which is an analog filter, are ideally flat, but in reality, they are not flat, similar to the LPF 142. On the other hand, there are cases where it is preferable that the analog signal An4 output from the audio I / O 16 is a signal that is a faithful digitization of the digital signal Dg1. For this reason, in this embodiment, the characteristics of the digital signal Dg1 that change as a result of being processed by the DAC 164 and the LPF 166 are cancelled in advance by the FIR filter 162, and the digital signal Dg1 is converted into an analog signal An4 and output.

[0030] When determining the characteristics of the FIR filter 162, the input terminal of the DAC 164 is disconnected from the output terminal of the FIR filter 162. The output terminal of the DAC 166 is disconnected from the input terminal of the re-amplifier .

[0031] The acquisition unit 168 supplies a digital test signal Dt1 to the input terminal of the DAC 164, and receives an analog signal Am1 from the output terminal of the LPF 166 and converts it into a digital signal. The test signal Dt1 is, for example, a digital source signal whose frequency is swept across the audible band and whose amplitude is uniform. When the test signal Dt1 is converted into an analog signal by the DAC 164 and filtered by the LPF 166, the filtered signal becomes a signal in which the frequency characteristics of the DAC 164 and the LPF 166 are imparted to the test signal Dt1. For this reason, the acquiring section 168 converts the analog signal Am1 into a digital signal, and compares the converted digital signal with the digital test signal Dt1. The acquisition unit 168 then obtains, for the digital signal Dm1, the frequency phase characteristic and the frequency amplitude characteristic of the digital signal obtained by converting the analog signal Am1. The acquisition unit 168 stores information that defines the inverse characteristics of the obtained frequency phase characteristic and frequency amplitude characteristic in the memory device M2 of the FIR filter 162. This causes the FIR filter 162 to have frequency characteristics defined by the stored information.

[0032] Although not specifically shown, when a filter coefficient specifying an inverse characteristic is set in the FIR filter 162, the digital signal Dg1 supplied to the input terminal In2 is converted into an analog signal An4 with approximately flat frequency phase characteristics and frequency amplitude characteristics.

[0033] Next, a usage example of the signal processing device 10 according to the embodiment will be described.

[0034] 7 is a diagram showing an example of connection to the signal processing device 10. In this connection example, a signal sent from an electric guitar 30 is supplied as an analog signal An1 to an input terminal In1 of the impedance conversion device 12, while a guitar amplifier 40 is connected to an output terminal Out1, and a digital signal Dg1 is recorded in a personal computer 50. The guitar amplifier 40 generally has a function of amplifying the analog signal and emitting sound from a built-in speaker.

[0035] In detail, the signal output when the user plays the electric guitar 30 is amplified and output by the guitar amplifier 40. That is, the user plays the electric guitar 30 while listening to the musical tones emitted from the guitar amplifier 40. An electric instrument such as the electric guitar 30 can produce musical tones without being connected to a guitar amplifier 40. However, there are various playing techniques that cannot be expressed with an electric instrument unless it is connected to a guitar amplifier 40. In order to check such playing techniques, it is almost essential to connect the electric instrument to the guitar amplifier 40, especially when recording music for a CD (Compact Disk) or the like. The electric guitar 30 is an example of an "electric musical instrument."

[0036] It is generally said that humans can recognize that there is a difference between two sounds in the audible range if there is a volume difference of 0.1 dB or more when focusing on the same frequency range. If the DC impedance at the input end In3 of the impedance conversion circuit 124 is 1 GΩ, the volume difference between analog signals An1 and An2 is suppressed to less than 0.1 dB when analog signal An1 branches into An2 and An3 at branching section 122. For this reason, in this embodiment, the signal processing device 10 is interposed between the electric guitar 30 and the guitar amplifier 40, but the effect thereof can be almost negligible compared to the case of a direct connection.

[0037] In this way, if the DC impedance in the impedance conversion circuit 124 is approximately 1 GΩ or more, the volume difference between the analog signals An1 and An2 is suppressed to less than 0.1 dB. In other words, the DC impedance being approximately 1 GΩ or more means that the difference between the analog signals An1 and An2 is not recognizable by humans.

[0038] Furthermore, when the signal output by playing the electric guitar 30 is amplified and output by the guitar amplifier 40, it may be recorded later for playback or detailed sound creation. In this embodiment, the analog signal An3 branched at the branching unit 122 is converted to low impedance by the impedance conversion circuit 124, and further converted to a digital signal Dg1 by the audio I / O 14 and recorded on the personal computer 50.

[0039] 8 is a diagram showing another example of connection to the signal processing device 10. This connection example is an example in which a digital signal Dg1 recorded by a personal computer 50 is supplied to an input terminal In2 of an audio I / O 16, converted into an analog signal by the audio I / O 16, and amplified and output by a guitar amplifier 40 connected to an output terminal Out3, that is, an example of playback.

[0040] 7, analog signal An1 output by playing electric guitar 30 branches into An2 and An3. Of these, analog signal An2 is output from guitar amplifier 40 with almost no change from analog signal An1, while analog signal An3 is converted to digital signal Dg1 by audio I / O 14 and recorded on personal computer 50. In audio I / O 14, changes in frequency characteristics caused by LPF 142 and ADC 144 are cancelled out later by FIR filter 146, so that analog signal An1 can be converted to digital signal Dg1 with little degradation (no effect applied) of dry sound. 8, the digital signal Dg1 recorded in the personal computer 50 is later converted to an analog signal by the audio I / O 16, and then further converted to high impedance by the re-amplifier 18, and is output from the guitar amplifier 40. In the audio I / O 16, the change in frequency characteristics caused by the DAC 164 and the LPF 166 is cancelled in advance by the FIR filter 164, so that the digital signal Dg1 can be faithfully converted to an analog signal. Therefore, in this embodiment, the sound output from the guitar amplifier 40 by playback as shown in FIG. 8 can be reproduced in almost the same way as the sound output from the guitar amplifier 40 by playing as shown in FIG.

[0041] The above-described embodiment may be modified in various ways. Specific modified aspects that may be applied to the embodiment are illustrated below. Two or more aspects selected from the following examples may be combined to the extent that they are not mutually contradictory.

[0042] Since the digital signal Dg1 recorded in the personal computer 50 is a dry sound with little degradation, it is easy to impart any desired amplifier characteristics to the digital signal Dg1 by, for example, executing an amplifier simulator of a DAW (Digital Audio Workstation) on the personal computer 50. In addition, any desired amplifier characteristics can be imparted by processing the digital signal Dg1 in the audio I / O 16.

[0043] A typical impedance conversion circuit not only converts a high-impedance analog signal to a low-impedance signal, but also has its own characteristics that can be used to create sound. The impedance conversion circuit 124 in the embodiment does not have such characteristics, but the recorded digital signal Dg1 is a dry sound without degradation. Therefore, the user can give the digital signal Dg1 the characteristics he or she desires using the DAW or the like, thereby expanding the range of sound creation.

[0044] In the embodiment, the electric guitar 30 has been described as an example of an electric musical instrument, but the electric musical instrument is not limited to the electric guitar 30. As an electric musical instrument that converts vibrations of a sound-producing body into an electric signal like the electric guitar 30, for example, a Hammond organ or a bass guitar may be used. In addition, as another electric musical instrument, an electone that converts electrical vibrations caused by an oscillator circuit into a tone color or sound may be used.

[0045] In the embodiment, the FIR filter 146 of the audio I / O 14 is configured to be set to the inverse characteristics of the frequency characteristics of the LPF 142 and the ADC 144. If the conversion accuracy of the ADC 144 is high and the frequency characteristics of the ADC 144 can be ignored, the FIR filter 146 may be configured to be set to the inverse characteristics of the frequency characteristics of only the LPF 142. Similarly, in the embodiment, the FIR filter 162 of the audio I / O 16 is configured to have the inverse frequency characteristics of the DAC 164 and the LPF 166 . If the conversion accuracy of the DAC 164 is high and the frequency characteristics of the DAC 164 can be ignored, the FIR filter 162 may be configured to have the inverse characteristics of the frequency characteristics of only the LPF 166 .

[0046] One or both of the FIR filters 146 and 162 can also be realized by software processing in the personal computer 50, for example. That is, it is not necessary to provide the FIR filter 146 inside the audio I / O 14, and the personal computer 50 may execute processing equivalent to the FIR filter 146. In particular, the personal computer 50 may perform processing equivalent to the FIR filter 146 on the digital signal output from the ADC 144, and store the processed signal as a digital signal Dg1 in an internal storage device of the personal computer 50. Note that in a configuration in which the FIR filter 146 is realized by software in the personal computer 50, a storage device inside the personal computer 50 may be used as the storage device M1.

[0047] Similarly, the FIR filter 162 does not need to be provided inside the audio I / O 16, and the personal computer 50 may execute processing equivalent to the FIR filter 162. In particular, the personal computer 50 may be configured to read the digital signal Dg1 from an internal storage device, perform processing equivalent to the FIR filter 162 on the read digital signal Dg1, and supply the processed signal to the DAC 164. In a configuration in which the FIR filter 162 is realized by software in the personal computer 50, a storage device inside the personal computer 50 may be used as the storage device M2. Furthermore, the personal computer that stores or reads out the digital signal Dg1 and the personal computer that executes the processes corresponding to the FIR filters 146 and 162 may be the same or different.

[0048] From the above description, preferred aspects of the present disclosure can be understood as follows, for example.

[0049] An impedance conversion device according to one aspect 1 of the present disclosure includes a first input terminal to which a first analog signal output from an electric musical instrument is input, a branching section to branch the first analog signal into a second analog signal and a third analog signal, a first output terminal to which the second analog signal is output, an impedance conversion circuit to convert the impedance of the third analog signal, and a second output terminal to which the impedance-converted analog signal is output, and the input impedance of the impedance conversion circuit is approximately 1 GΩ or more. According to the impedance conversion device of the first aspect, by connecting a guitar amplifier to the first output terminal, musical tones produced by playing an electric musical instrument can be emitted through the guitar amplifier, and the impedance of an analog signal output from the electric musical instrument can be converted and output. At this time, the impedance of the first analog signal output from the electric musical instrument can be output as the second analog signal almost unchanged without changing the impedance.

[0050] A signal processing device according to a second aspect includes the impedance conversion device according to the first aspect and a first input / output device that converts an analog signal output from the second output terminal into a digital signal. The signal processing device according to the second aspect can convert an analog signal output from an electric musical instrument into a digital signal. The audio I / O 14 is an example of a first input / output device, and the audio I / O 16 is an example of a second input / output device.

[0051] In a signal processing device according to a specific aspect 3 of aspect 2, the first input / output device has an A / D conversion unit that converts an analog signal output from the second output terminal into a digital signal, and a first characteristic imparting unit that imparts a first characteristic to the digital signal converted by the A / D conversion unit, the first characteristic being an inverse characteristic of a frequency characteristic in a path from the second output terminal to an output terminal of the A / D conversion unit. According to the signal processing device according to aspect 3, it is possible to cancel the frequency characteristic in an impedance conversion circuit or the A / D conversion unit when converting an analog signal into a digital signal.

[0052] In the signal processing device according to a fourth specific example of the third example, the first characteristic includes an amplitude change characteristic with respect to frequency and a phase change characteristic with respect to frequency.

[0053] A signal processing device according to a fifth specific example of the fourth example further includes a characteristic acquisition unit that acquires the first characteristic.

[0054] In the signal processing device according to a sixth specific aspect of the fourth aspect, the first characteristic applying section includes an FIR filter.

[0055] A signal processing device according to a specific embodiment 7 of embodiment 3 further includes a second input terminal to which a digital signal is input, a second input / output device to convert the digital signal input to the second input terminal into a fourth analog signal, a reamplifier unit to convert the impedance of the fourth analog signal, and a third output terminal to which a signal whose impedance has been converted by the reamplifier unit is output.

[0056] In a signal processing device according to another specific aspect 8 of aspect 7, the second input / output device has a second characteristic imparting unit that imparts a second characteristic to a digital signal input to the second input terminal, and a D / A conversion unit that converts the digital signal to which the second characteristic has been imparted into the fourth analog signal.

[0057] In a signal processing device according to a ninth aspect which is a specific example of the eighth aspect, the second characteristic is an inverse characteristic of a frequency characteristic in a path from an input terminal of the D / A conversion unit to the third output terminal. [Explanation of symbols]

[0058] 10: signal processing device, 12: impedance conversion device, 14, 16: audio I / O, 18: reamplifier, 142, 166: LPF, 144: ADC, 146, 162: FIR filter, 148, 168: acquisition unit.

Claims

1. a first input terminal to which a first analog signal output from an electric musical instrument is input; a branching unit that branches the first analog signal into a second analog signal and a third analog signal; a first output terminal for outputting the second analog signal; an impedance conversion circuit that converts the impedance of the third analog signal; a second output terminal for outputting the impedance-converted analog signal; Including, The input impedance of the impedance conversion circuit is approximately 1 GΩ or more. Impedance conversion device.

2. The impedance conversion device according to claim 1 ; a first input / output device for converting an analog signal output from the second output terminal into a digital signal; Includes Signal processing device.

3. The first input / output device is an A / D converter that converts an analog signal output from the second output terminal into a digital signal; a first characteristic imparting unit that imparts a first characteristic to the digital signal converted by the A / D conversion unit; having The first characteristic is The inverse characteristic of the frequency characteristic in the path from the second output terminal to the output terminal of the A / D conversion unit. The signal processing device according to claim 2 .

4. The first characteristic includes an amplitude change characteristic with respect to frequency and a phase change characteristic with respect to frequency. The signal processing device according to claim 3 .

5. A characteristic acquisition unit for acquiring the first characteristic The signal processing apparatus of claim 4 further comprising:

6. The first characteristic applying unit includes an FIR filter. The signal processing device according to claim 4.

7. a second input terminal to which a digital signal is input; a second input / output device for converting a digital signal input to the second input terminal into a fourth analog signal; a reamplifier unit that converts the impedance of the fourth analog signal; a third output terminal to which a signal whose impedance has been converted by the reamplifier unit is output; The signal processing device according to claim 3 , further comprising:

8. The second input / output device is a second characteristic imparting unit that imparts a second characteristic to the digital signal input to the second input terminal; a D / A conversion unit that converts the digital signal to which the second characteristic has been imparted into the fourth analog signal; The signal processing device according to claim 7, further comprising:

9. The second characteristic is The inverse characteristic of the frequency characteristic in the path from the input terminal of the D / A conversion unit to the third output terminal. The signal processing device according to claim 8.

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