JPS5825439Y2 - electric piano weak tone circuit - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a low tone circuit for an electric piano that can smoothly change the volume of the electric piano.

In general, an electric piano has a mechanical structure similar to that of a natural piano, and the strings stretched on a frame are struck with a hammer by operating a key, causing the strings to vibrate.

The vibrations of the strings are then detected by a pickup, converted into an electrical signal, amplified by an electrical circuit, and then emitted from a speaker.

For conventional electric pianos, in order to obtain a weak tone, just like a natural piano, in the upright type, pressing the mute pedal brings the hammer closer to the strings to shorten the string striking distance. The grand type used a method in which the relative position of the hammer to the string was shifted.

However, these systems have the drawbacks that in the case of an upright piano, play (gap) occurs in the action mechanism, making it difficult to touch the keys, and in the case of a grand piano, the mechanism becomes complicated and costs increase.

Since an electric piano has an electric circuit, a method has been considered to obtain a weak tone using only the electric circuit without using such mechanical means.

Figures 1A and 2 are circuit diagrams of the soft tone circuit of a conventional electric piano.

In FIG. 1, reference numeral 1 denotes a mute pedal, and when this pedal is depressed, the variable resistor VR is interlocked and the sliding terminal is moved to the ground side.

Therefore, the signal input from the input terminal IN is attenuated and output from the output terminal OUT, resulting in a weak sound state.

When the mute pedal 1 is released, the sliding terminal of the variable resistor VR returns to its original position and becomes normal.

Note that Ri y R2 is a resistor, and C is a capacitor.

In FIG. 2, when the mute pedal 1 is depressed, the switch SW is operated to close in conjunction.

Therefore, in a normal state, the input signal passes through the resistor R3 and is output from its 11 output terminal OUT, but when the switch SW closes, the voltage is divided and attenuated by the resistors R3 and R4, resulting in a weak sound state.

However, if such a low tone circuit is used to obtain a low tone condition for an electric piano, there will be a problem in that the volume level will change abruptly at the time of switching.

The effect will be explained below.

Figure 3 is a diagram showing the relationship between mute pedal operation and volume when a mechanical dampening mechanism similar to that of a natural piano is provided.
The figure is a diagram showing the relationship between mute pedal operation and volume when a conventional low tone circuit is used.

In FIG. 3, at time T1, the mute pedal is depressed to create a soft tone, and at time T2, when a certain key is struck, a soft level sound is produced.

This sound will gradually attenuate, but if you release the mute pedal at T3, the hammer will return to its normal position, but the vibrating string will not be affected in any way, so the sound produced at T2 will be Part 11 Lasts.

If you strike the next key at T4, the hammer position is already in the normal state at T3, so the sound will be produced at a normal level.

In FIG. 4, similarly, at time T1, the mute pedal is depressed to put the mute circuit into a mute state, and when the key is struck at time T2, a mute level sound is produced.

Next, when the mute pedal is released at time T3, the mute circuit returns to the normal state, and the volume level immediately rises to the same level as if the sound was produced in the normal state at time T2.

If you hit the next key at T4, a normal level sound will be produced.

In this way, with electric pianos that use conventional weak tone circuits, when the mute pedal is operated, the volume level changes rapidly at that point, resulting in discontinuous and unsmooth performances.
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This idea was made in view of the above points, and its purpose is to configure the weak sound state with an electric circuit, so the mechanism is simple and the cost is low, and moreover, there is no discontinuity in the volume level. 'The purpose is to provide a weak tone circuit for electric pianos.

To achieve this objective, the present invention uses a time delay effect to smooth out changes in the magnitude of the output signal when switching between the normal state and the low tone state.

This invention will be explained in detail below based on the drawings.

FIG. 5 is a circuit diagram of an embodiment of the soft tone circuit of the electric piano according to this invention.

In the figure, R11, R13, R14, and R15 are resistors, and R12 is a resistor of CDS (cadmium sulfide), which is a photoconductive element whose resistance value changes depending on the illuminance of the received light.

C1 is a capacitor, Dl is a light emitting diode, Q is a field effect transistor, and SWl is a switch as a switching means that operates in conjunction with mute pedal 1.
It closes when you step on it, and opens when you release it.

The light emitting diode D1 and the resistor R12 form a pair and constitute a photocoupler.

Electrical signals input from input terminal IN are connected to resistors R11 and R12.
However, under normal conditions, the field effect transistor Q is non-conductive and the light emitting diode D1 is
Since it does not light up, the value of the resistor R12 becomes relatively large, and the input signal is output approximately 11 times, so that an electrical signal with a normal volume is output.

The resistor R15 serves to limit the drain current by applying a self-bias when the field effect transistor Q is turned on.

Next, in order to make the sound weak, when the mute pedal 1 is depressed, the switch SW1 is closed and the resistor R13 is connected to the power supply B in series with the capacitor C1.

The voltage at the gate of the field effect transistor Q gradually increases due to the time constant of the resistor R13 and the capacitor CI, and accordingly, the drain current gradually increases and the light emitting diode D1 begins to shine.

As a result, the resistance value of the resistor R12 gradually decreases, and the voltage of the electrical signal output from the output terminal OUT decreases.

Eventually, when the capacitor C1 is completely charged, the gate voltage of the field effect transistor Q becomes constant at the value divided by the resistors R13 and Rt4, and the circuit is kept in a quiet state and the performance is performed at a low volume.

Next, when the mute pedal 1 is released and the normal state (F) is established, the switch SW1 opens and the circuit from the resistor R13 is disconnected.

However, the charge stored in capacitor CI is
1 and the time constant of the resistor R14, the gate voltage of the field effect transistor Q gradually decreases.

Therefore, contrary to the above, the amount of light emitted from the light emitting diode D1 gradually decreases, the resistance value of the resistor R12 increases, and the output terminal O
The voltage of the electrical signal output from the UT increases.

Eventually, when the capacitor C1 is completely discharged, the gate voltage of the field effect transistor Q becomes zero, the circuit is maintained in a normal state, and the performance is performed at a normal volume.

Here, the transistor 202 is a light emitting diode D1. Resistance R1
t, R12, etc. constitute a volume converting means, and resistor R13+R□4.

A time delay means is constituted by the capacitor C1 and the like.

FIG. 6 is a diagram showing the relationship between the operation of the mute pedal and the volume.

Assuming that the mute pedal is depressed at time T1 and the mute circuit is already in a mute state, if a key is struck at time T2, a sound is produced at a mute level.

Next, when the mute pedal is released at T3 during the decay, the switch SW1 opens, but the circuit gradually returns to a normal state due to the time constant of the capacitor C1 and the resistor R14, so the volume changes more slowly than it should.

Then, when you hit the next key at T4, a nearly normal level of sound comes out.

If you strike the key after a sufficient period of time, the sound will be at a completely normal level.

Since there is no sudden change in volume at T3 as shown in FIG. 4, switching of the weak tone circuit is hardly noticeable.

Next, when the mute pedal is depressed again at T5 to make the sound mute, the switch SWt closes, but the circuit gradually becomes the mute state due to the time constant of resistor R13 and capacitor C1, so the volume does not drop suddenly but gradually. I'm going to go.

Then, when you hit the next key at T6, a nearly soft-tone sound comes out.

In this case, if you strike the key after a sufficient period of time, the sound will be completely soft.

In this way, even if the low-tone circuit is switched between the normal state and the low-tone state at any time, there is no sudden change in volume at the time of switching, and the sound is hardly felt by the ears.

In the case of the numerical example shown in FIG. 5, the time for switching between the normal state and the low sound state can be delayed by about 1 second in response to pedal operation.

Resistor R1 which acts as a time delay along with capacitor CI
Although 3h and R14 have been described as fixed resistors, they can be made into variable resistors and the time delay amount can be finely adjusted depending on when the □ NEET pedal is pressed and when it is released.

FIG. 7 is a circuit diagram of another embodiment, in which the switch SW2 interlocked with the mute pedal 1 is of a changeover type, and the resistor R14 is disconnected from the circuit in a weak tone state.

The operation is similar to the previous embodiment. It is also possible to add a charge discharging diode D2 to the -1 resistor R14 to drastically change the rise and fall at the time of switching, thereby producing a different effect.

Although a field-effect transistor is used for the button Q, it can be constructed using an ordinary transistor or an IC.

As described above, according to the mute circuit of the electric piano according to this invention, the mute function can be provided by an electric circuit instead of a mechanical one, so the mechanism is simple and the cost can be reduced, and the output is output when the mute pedal is operated. By making the change in the signal level gentle, a time delay is provided when switching between the normal state and the weak sound state, allowing smooth volume switching similar to that of a natural piano.

[Brief explanation of the drawing]

Figures 1 and 2 are circuit diagrams of conventional soft tone circuits, Figure 3 is a diagram showing the relationship between mute pedal operation and volume on a natural piano, and Figure 4 is a diagram showing the relationship between mute pedal operation and volume of a conventional soft tone circuit. Figure 5 is a circuit diagram of one embodiment of the soft tone circuit of the electric piano according to this invention, Figure 6 is a diagram showing the relationship between the operation of the mute pedal and volume, and Figure 7 is a diagram showing the relationship between volume. FIG. 3 is a circuit diagram of an embodiment of the invention. 1...Beyuto pedal, R1t, R13, R14? R
159...Resistance, R12...Resistance of cds, C1・
...Capacitor, Dl...Light emitting diode, Q...
Field effect transistor, SWl...switch.

Claims (1)

[Scope of utility model registration request] A mute circuit for an electric piano in which switching between a normal state and a mute state is performed by an electric circuit includes a switching means that operates in conjunction with a mute pedal, and the magnitude of an output signal is changed in accordance with the operation of this switching means. 1. A weak tone circuit for an electric piano, comprising: a volume converting means; and a time delay means that is activated by the operation of the switching means and smoothes changes in the magnitude of the output signal.