JPH0634168B2 - Electronic musical instrument - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic musical instrument, and more particularly to an electronic musical instrument that digitally generates a musical sound.

2. Description of the Related Art In recent years, many electronic musical instruments digitally generate musical tones. Such an electronic musical instrument is disclosed in Japanese Patent Laid-Open No. 58-887.
No. 90 publication. A block diagram is shown in FIG. 3 and will be described. The waveform generator 1 generates periodic waveform data based on the note octave information.
The envelope generator 2 generates an envelope signal based on the key depression information. Here, as the envelope signal, the envelope waveform previously input to the memory is sequentially read from the rising portion by the key depression and is output. The multiplier 3 multiplies the waveform data generated by the waveform generator 1 and the envelope signal generated by the envelope generator 2, and the tone signal is converted into an analog signal by a digital-analog converter (hereinafter referred to as DAC) 9. Output as.

Problems to be Solved by the Invention The dynamic range of the generated musical sound is determined by the number of bits of the signal (musical sound signal) that is finally output. With the above configuration, however much the number of output bits is increased, It depends on the bit precision of the DAC connected to. That is, even if the number of bits of the DAC is increased according to the number of bits of the musical tone signal, the dynamic range is determined by the bit precision of the DAC. Therefore, a high dynamic range can be obtained by increasing the bit precision of the DAC.
100 dB for musical instruments that require more than 100 dB per sound,
That is, a DAC having a bit precision of about 17 bits is required, and there is a drawback that the cost becomes very high.

In view of the above problems, the present invention is a DA with low bit precision.
An object of the present invention is to provide an electronic musical instrument that can generate musical tones with a wide dynamic range even with C.

Means for Solving the Problems In order to solve the above problems, the electronic musical instrument of the present invention has a waveform generator that generates a waveform based on a binary logic signal, and an envelope generator that generates an envelope signal in response to a key press. , A multiplier for multiplying the waveform by the envelope signal, a means for giving an offset to the output of the multiplier based on the envelope signal, and an output by the means for giving an offset to an analog signal Digital-to-analog converter and the offset,
It has means for removing it from the output of the digital-analog converter.

Effect The present invention has the above-described configuration, which provides the DAC with an offset as the envelope signal is attenuated.
Since the upper bits given to the above are fixed and only the lower bits are changed, the influence of the error due to the upper bits does not appear in the output. Therefore, even a DAC with a low bit precision can generate a musical sound with a wide dynamic range.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of an electronic musical instrument according to the present invention. In FIG. 1, reference numeral 1 is a waveform generator, which generates a waveform based on digital data. Reference numeral 2 denotes an envelope generator, which generates an envelope signal according to key depression information. A multiplier 3 multiplies two types of input signals. An adder 4 multiplies the output of the multiplier 3 and the envelope signal inverted by the inverter 5. Reference numerals 6 and 7 are DACs. An analog mixer 8 mixes the two series of analog signals output from the DAC 6 and the DAC 7.

Next, the operation of the electronic musical instrument shown in FIG. 1 will be described. The waveform generator 1 here generates a periodic waveform (see FIG. 2).
(a)). The envelope generator 2 generates an envelope signal according to the key depression information (Fig. 2 (b)). One of the envelope signals is to the multiplier 3 and the other is to the inverter 5.
Is given to. The multiplier 3 multiplies the waveform and the envelope signal and outputs the result (FIG. 2 (c)). On the other hand, the inverter 5 inverts the envelope signal (FIG. 2 (d)) and inputs this value as an offset to the adder 4 and the DAC 7. The adder 4 adds the output of the multiplier 3 and the offset of the inverter 5 and outputs the result (FIG. 2 (e)).
The DAC 6 then converts the output of the adder 4 into an analog quantity. This signal is just a musical tone signal with a so-called pedestal.

In this way, since the data is fixed from the upper bits as the waveform gradually attenuates, the volume of the signal output from the DAC 6 gradually decreases even if the bit precision is not so high, and a wide dynamic range is obtained. be able to. A brief explanation of this is as follows. That is: The DAC output has a bit precision of δ _n for each bit.
Can be expressed as

However, b _m : input for DAC bit m N: number of bits of DAC Therefore, assuming that the input of DAC is centered on “0” (zero), normally the MSB (most significant bit) input of DAC is The input is “01 ……
1 ”(-1 in decimal) and“ 10 ... 0 ”(0 in the same)
It will be going back and forth between. Substituting these two values into equation (1), Here, if it is assumed that a 12-bit DAC has 8-bit precision, then −1/512 <δ _n <1/512, so (DAC output when input = −1)> (when input = 0 The DAC output) comes out. However, when an offset is given, the upper bits of the DAC input are fixed, so that the magnitude relationship of the input and the magnitude relationship of the output is not reversed, and the output of the dynamic range according to the number of bits of the DAC is obtained. It is a thing.

On the other hand, the DAC 7 converts the output of the inverter 5 shown in FIG. 2 (d) into an analog amount and outputs it. Therefore, the output of the analog mixer 8 becomes the signal shown in FIG. 2 (f), and a tone signal without a pedestal can be obtained.
With this configuration, DA with low bit precision
It is possible to obtain a tone signal having a high dynamic range by using C.

In this embodiment, the inverted envelope signal is simply added to the output of the multiplier 3 (FIG. 2 (c)). However, the inverted envelope signal is changed in level by bit shift or the like. It goes without saying that a reduced size may be used.

EFFECTS OF THE INVENTION As described above, according to the present invention, a waveform generator that generates a waveform based on a binary logic signal, an envelope generator that generates an envelope signal in response to a key press, and a multiplication of the waveform and the envelope signal. And a means for giving an offset to the output of the multiplier based on the envelope signal, a digital-analog converter for converting the output by the means for giving an offset into an analog signal, and the offset, By having means for removing from the output of the digital-analog converter, it is possible to obtain a tone with a high dynamic range using a DAC with low bit precision. In particular, when performing D / A conversion using an R-2R resistance ladder, it is only necessary to connect low-precision resistors in a ladder shape, so that a musical tone signal with a high dynamic range can be obtained at low cost.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an electronic musical instrument according to an embodiment of the present invention, FIG. 2 is a waveform diagram showing an output waveform of each block in FIG. 1, and FIG. 3 is a block showing an electronic musical instrument in a conventional example. It is a figure. 1 ... Waveform generator, 2 ... Envelope generator, 3 ...
Multiplier, 4 ... Adder, 6, 7 ... DAC, 8 ... Analog mixer.

Claims (1)

[Claims] 1. A waveform generator for generating a waveform based on a binary logic signal, an envelope generator for generating an envelope signal in response to a key press, and a multiplier for multiplying the waveform and the envelope signal. Means for giving an offset to the output of the multiplier based on the envelope signal; a digital-analog converter for converting the output of the means for giving an offset into an analog signal; and an output of the digital-analog converter for the offset. An electronic musical instrument characterized by having means for removing from the electronic musical instrument.