JPS5841594Y2 - signal mixing circuit - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a signal mixing circuit for an electronic musical instrument with an extremely simple configuration.

As a conventional signal mixing circuit for an electronic musical instrument, the one shown in FIG. 1 or 2 is known.

In the circuit diagram shown in FIG. 1, A1. A2. A8 indicates the application terminal of the pulse train corresponding to the high pitch of different tones, and on the other hand, the attack signal applied to point C when the key is pressed is differentiated and rectified, and D
Obtain the envelope waveform of the point.

The waveform at point D is modulated by the pulse train at each point B1 t B2 s B3, resulting in a waveform in which rectangular waves are intermittently attenuated, and these are mixed to obtain the waveform shown at point E.

This circuit requires at least two diodes for each signal line.

Further, in the circuit shown in FIG. 2, FET1 to FET3 are P-channel MO8FETs, and the others are the same as in FIG. 1.

In FIG. 2, a sufficient current initially flows through the FET due to the envelope waveform, and the current gradually decreases.

Therefore, if the signals are mixed at the drain electrode of the FET, the waveform shown at point E can be obtained.

This circuit requires an FET to be connected to each pulse train signal input line, and if the number of signal input lines increases, it becomes expensive.

Furthermore, when the signal amplitude drops to the cutoff voltage in each FET, the amplitude suddenly drops to zero level, which has the disadvantage that the mixed signal sounds extremely unnatural.

An object of the present invention is to provide a signal mixing circuit for an electronic musical instrument with an extremely simplified configuration.

The embodiment of the present invention shown in FIG. 3 will be described below.

Pulses corresponding to different pitches are A1 p A2- A3
Differentiate the attack signal applied to the y point and when one key is pressed.
A rectified envelope waveform is obtained and applied to the FET from point D.

One FET as a gate element is a P-channel MO8 type, and is DC-controlled to be sufficiently conductive before application of the envelope waveform.

(At this time, no output signal is generated at output point E). The rise of the envelope waveform causes the FET to be in a -open (OFF) state, and then a current begins to flow through the envelope waveform in inverse proportion to the current.

Therefore, B, , B2. The waveform at point B3 is 8
As shown in the waveform diagram shown next to the four points, a rectangular wave modulated by the envelope waveform is obtained, and these are mixed to obtain the waveform at point E.

Even if the number of AHy A2 y A3 points, that is, the number of input pulse trains is increased, the number of resistive elements and diodes only increases slightly, and a large number of expensive gate elements are not required, so the configuration is extremely simple.

It is also possible to use a bipolar transistor as the gate element by applying an appropriate DC bias.

By using a FET, the input impedance seen from the envelope waveform application terminal can be maintained high, and since the drain terminal is grounded, there is no step in the waveform caused by the cutoff voltage that occurs in conventional circuits. It never happens.

In this way, according to the present invention, a signal mixing circuit with an extremely simplified configuration can be obtained at low cost, and even if the number of input pulse waveform signal lines increases, there is no need to increase the number of gate elements. The circuit can be easily adjusted, and in the conventional example shown in Figure 1, the input impedance of the circuit would drop and waveform distortion would occur, but with the present invention, there is no such risk and a good mixed waveform can be obtained. have an effect.

[Brief explanation of the drawing]

1 and 2 are diagrams showing a conventional signal mixing circuit, and FIG. 3 is a circuit diagram showing an embodiment of the present invention. AHm A2 p A3... Pulse train application terminal, C... Attack signal application terminal, E...
・Signal mixing circuit output terminal.

Claims (1)

[Scope of utility model registration request] In a circuit in which a gate circuit modulates pulse train signals corresponding to different pitches according to an envelope waveform obtained from an attack signal when a key is pressed in an electronic musical instrument, and then mixes the signals, the gate circuit is configured with a single FET element, and Signal mixing characterized in that the attack signal is applied to the gate electrode, the drain electrode is grounded, and the source electrode is connected to the intermediate point of each signal line mixing resistor of the pulse train through each irreversible element. circuit.