US3656008A - Gate circuit for electronic musical instruments - Google Patents

Gate circuit for electronic musical instruments Download PDF

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Publication number
US3656008A
US3656008A US5851A US3656008DA US3656008A US 3656008 A US3656008 A US 3656008A US 5851 A US5851 A US 5851A US 3656008D A US3656008D A US 3656008DA US 3656008 A US3656008 A US 3656008A
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Prior art keywords
transistors
terminal
gate circuit
pair
voltage source
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Expired - Lifetime
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US5851A
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English (en)
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Yoshiyuki Nakagomi
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Hitachi Ltd
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Hitachi Ltd
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    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
    • G10H1/00—Details of electrophonic musical instruments
    • G10H1/02—Means for controlling the tone frequencies, e.g. attack or decay; Means for producing special musical effects, e.g. vibratos or glissandos
    • G10H1/04—Means for controlling the tone frequencies, e.g. attack or decay; Means for producing special musical effects, e.g. vibratos or glissandos by additional modulation
    • G10H1/053—Means for controlling the tone frequencies, e.g. attack or decay; Means for producing special musical effects, e.g. vibratos or glissandos by additional modulation during execution only
    • G10H1/057—Means for controlling the tone frequencies, e.g. attack or decay; Means for producing special musical effects, e.g. vibratos or glissandos by additional modulation during execution only by envelope-forming circuits

Definitions

  • ABSTRACT Foreign Application Priority Data
  • a sustaining gate circuit for musical instruments comprising a differential amplifier stage including a pair of transistors the 1969 Japan "44/8148 emitters of which are connected in common and a constant current transistor connected to said commonly connected [52] US. Cl ..307/268, 84/ l .26, 330/69 emitters a key switch for applying the gating signal to the base ll.”- Cl. of aid constant current transistor and a time-delay circuit [58] Field of Search ..84/ 1.26, 1.13; 330/69; n t d in the base circuit of said constant current 307/268, 293, 244 transistor for obtaining sustaining effect in fade-out of the output.
  • a desired signal or signals are selected from the electric signals of various frequencies generated from tone generators by pressing keys for playing the instrument. This selection is done through an electronic gate circuit driven by the mechanical action of pressing keys.
  • Such a gate circuit is provided for each signal and thus the number thereof becomes vary large. Therefore, such a gate circuit should have a simple structure for minimizing the size and enhancing the reliability thereof.
  • the outputs of respecthe output to form an electric signal waveform corresponding to a desired sound and this mixed output is transmitted to a timbre circuit.
  • the total noise level at the output of the gate circuit system is the sum of noise level of the respective gate circuits.
  • the signal to noise ratio of the total gate circuit system depends on the ratio of the output signal level of the respective gate circuits when the gates are open or in the on-state with respect to that when they are closed or in the off-state, i.e. on-off ratio.
  • on-off ratio the ratio of the output signal level of the respective gate circuits when the gates are open or in the on-state with respect to that when they are closed or in the off-state.
  • musical sounds fade out naturally with the appropriate reverberation.
  • the output of a gate circuit should not diminish immediately but decrease exponentially at a constant rate when a corresponding key switch is turned off.
  • the on-off ratios of the conventional gate circuits are not much larger than 50 db and their damping characteristics after turning off the key switches take .deformed exponential shapes so that the output sound diminishes unnaturally.
  • the appropriate amount of higher harmonics should be mixed with the fundamental tone. Since a gate circuit is provided for each signal frequency and a time difference may occur in the gating action of the respective gate circuits, sometimes the desired electric signal waveform corresponding to the desired musical sound is not produced. Further, an output sound may be deformed since similar damping characteristics are hard to be obtained in the respective gate circuit.
  • An object of the invention is to provide a gate circuit having a large on-off ratio.
  • Another object of the invention is to provide a gate circuit having a sustaining effect in which the output of a gate decreases exponentially upon turning off a corresponding key switch and the length of time required for the output to decrease to a desired level can be arbitrarily and easily changed.
  • a further object of the invention is to provide a gate circuit which can simultaneously gate a plurality of input signals by one key switch and which can give a common damping characteristic to a plurality of output signals corresponding to said plurality of input signals.
  • Yet a further object of the invention is to provide a sustaining gate circuit operated by a small electric current and capable of damping the output exponentially without any distortion.
  • Another object of the invention is to provide a gate circuit for use in electronic musical instruments which is especially effective when applied to an integrated circuit.
  • a difierential amplifier can be used.
  • a differential amplifier is formed by connecting the emitter electrodes of a pair of transistors in com mon and further connecting another transistor working as a constant current source to said common emitter electrode to vary the mutual conductance or the transmission conductance of the differential amplifier stage by the current flowing through said constant current transistor thereby to perform a gating action.
  • a control signal is cut off by opening the key switch connected to the constant current transistor, the current flowing through the constant current transistor decreases exponentially by the effect of a time delay circuit having a sustaining function and connected to the input electrode of the constant current transistor and accordingly the mutual conductance of the differential amplifier stage decreases exponentially.
  • a desired output characteristic is obtained at an output terminal of the differential amplifier stage.
  • the time constant of the time delay circuit used as an envelope forming circuit can be arbitrarily altered by adjusting the duty cycle of the control pulse signal to be applied to the switching element.
  • FIG. 1 is a circuit diagram of an embodiment of a gate circuit for electronic instruments according to the invention
  • FIG. 2 is a circuit diagram of another embodiment of a gate circuit for electronic instruments according to the invention.
  • FIGS. 3a to 30 show signal waveforms detected at various points in the circuit shown in FIG. 1.
  • FIG. 1 shows a circuit which gates or selects with respect to time an electrical signal from a plurality of electrical signals in the frequency range of 40 to 4000 Hz by a gate signal supplied through one key switch.
  • the circuit comprises active elements Q and O having, respectively, input, output and common electrodes, each active element being a bipolar transistor having a base, a collector and an emitter electrode.
  • a differential amplifier is formed by the transistors Q and G with the base electrode of one transistor 0 A connected to an input terminal 1, the collector electrode of the other transistor 0 connected to an output terminal 2 and the emitters of both transistors 01.. and 0 connected in common. To this common connection point, the collector of another transistor 0 is connected.
  • the collector electrode of the transistor 0 A is connected to a first voltage supply terminal 3 applied with voltage V and the collector electrode of the transistor 0 is also connected to the first terminal 3 through a resistance R
  • the base electrodes of the transistors Q14 and Q are connected to a second voltage supply terminal 4 applied with voltage V through resistances R and R respectively, so as to apply a certain biasing voltage.
  • the emitter of the transistor O is connected to a reference voltage terminal 6 through an emitter resistance R
  • the base electrode of the transistor 0 is on one hand connectedthrough a resistance R to a key switch S which is interlocked with one of the keys of the instrument and connected to the second terminal 4 via terminal 8 through a forwardly biased diode D and on the other hand connected to an envelope forming circuit comprising a capacitance C a diode D resistances R and R and a transistor 0., and working as a time delay circuit.
  • the diode D is inserted between the base of the transistor Q34 and the reference voltage terminal 6 through the resistance R and the switching transistor O in a direction so as to be biased in the same direction as that of the base-emitter junction of the transistor Q
  • the base electrode of the switching transistor 0. is connected through a resistance R, to a terminal 5 for introducing control pulse input.
  • the capacitor C is connected between the reference voltage terminal 6, thereby also to the emitter electrode of the transistor 04.
  • An input signal is introduced from an input terminal 1A to the input electrode 1 through a capacitor C and the output signal is derived from the output electrode 2 to an output terminal 2A through a capacitor C
  • the diode D is inserted as shown in the figure so as to decrease the emitter voltage of the transistors Q and Q which is equal to the collector voltage of the transistor Q to a value not more than the base voltage of the transistor Q Without this diode D the base voltage of the transistor Q is maintained higher than the collector voltage of the transistor Q34- Therefore, when the key switch S is opened or turned off, a saturation current flows through the transistor Q until the base voltage becomes lower than the collector voltage.
  • the use of the diode D prevents this phenomenon and is effective to decrease the output current smoothly when the key switch S is opened.
  • the diode D prevents such a phenomenon that when the key switch S is opened and the base voltage of the transistor decreases exponentially, the base voltage of the transistor Q rapidly becomes smaller than the threshold voltage V of the transistor 0,, due to the fact that the transistor Q is in the on-state. Without this diode D though the output decreases exponentially until the base voltage of the transistor Q reaches the threshold voltage V,,,, since the base voltage decreases further on, the output is rapidly damped and the sound disappears unnaturally. By the insertion of diode D having a threshold voltage substantially equal to that of the transistor Q the base voltage of the transistor Q is held substantially at the threshold voltage, therefore a damping characteristic with a close approximation to the exponential function is obtained.
  • the resistance R is connected in series to the key switch S to prevent the transistor 0,, from an input signal being applied suddenly when the key switch S is turned on and to generate a sound smoothly becoming louder with a certain rising time length.
  • FIGS. 3a to 3c show the waveforms of the input signal voltage V the base voltage V of the transistor O and the output signal voltage V,,,,,, respectively, with respect to time.
  • Letter T indicates the sustaining length of time.
  • the collector Q works as a constant current source allowing the collector current I to flow which is the sum of the emitter currents l and 1, flowing through the transistors Q and Q If the current I increases, the other current l decreases since the sum is maintained constant.
  • the differential amplifier stage has its operational voltage point determined by the second source voltage V transmits the input signal to the output terminal 2, the signal being amplifier according to the mutual conductance g determined by the collector current I
  • the output signal voltage appearing at the output electrode 2 is applied to the output terminal 2A through the capacitor C
  • the differential amplifier stage performs a switching action by controlling the total emitter current of the stage by changing the base voltage level of the transistor Q In this embodiment, an on-off ratio above 100 db was obtained.
  • the switching element 0 which is a switching transistor in this embodiment is used to adjust the sustaining time length T arbitrarily.
  • the base voltage of the transistor 0 decreases according to the discharge characteristic of the capacitor storing a charge therein featured by the time constant of the circuit including the capacitor C
  • the capacitor C can be sufiiciently discharged even by a small current.
  • the effective time constant 1 can be arbitrarily varied by arbitrarily selecting the duty cycle of the control pulse signal, d (expressed by pulse width (sec.)Iperiod (sec.) for a square pulse).
  • the effective time constant 1' is determined as the product of the capacitance C, and the resistance R, of the envelope forming circuit, and the duty cycle d, that is, F C -R 'd. Therefore, a desired time constant and a desired sustaining time length T can be obtained by appropriately varying the duty cycle d.
  • a square wave pulse train having a duty cycle of l to 50 percent, a frequency of 40 KHz and a peak voltage of 10V is applied to the terminal 5 in this embodiment.
  • FIG. 2 shows another embodiment of the invention in which transistors Q Q and Q forming a similar circuitry as that of the transistors Q Q and O of the former embodiment are added to the circuit. These two circuits are connected in parallel to the voltage source V
  • An envelope forming circuit comprising a capacitance C a diode D resistances R and R and a transistor 0,, is connected to the base electrodes of the transistors Qsx and Q38 in common.
  • a series connection of a key switch S, a diode D and a resistance R is also connected to the base electrodes of the transistors Q and Q35.
  • two kinds of electrical signal are subjected to gating operation by one key switch S. The operation of the circuit of FIG.
  • FIG. 2 shows a gating circuit for two input signals to be applied to the terminals 1A and 1B respectively
  • the number of the input signals can be arbitrarily increased, according to necessity, by connecting the desired number of circuits constituted by the transistors Q Q and Q shown in FIG. 1 in parallel similarly as is shown in FIG. 2.
  • the gate circuit of the invention is especially effective when applied in an integrated circuit.
  • transistors to be used for a differential amplifier stage are formed in a unitary semiconductor body to be mutually adjacent thereto so that various characteristics of the transistors, such as output characteristic or current amplification coefficient can be easily made uniform.
  • the gate circuit of this invention does not need a large resistance, the integration thereof is easy in this respect, too.
  • the diodes D, and D preferably have characteristics which are compatible with those of the base-emitter junction of the transistors Qm and Q respectively, from the standpoint of their function.
  • the transistors and the diodes are preferably formed simultaneously in a unitary semiconductor body. In integrated circuits, those portions as enclosed by the dotted line in FIGS. 1 and 2 may be formed in a single semiconductor.
  • the sustaining gate circuit of the invention is very effective for use in electronic musical instruments.
  • a gate circuit comprising:
  • a pair of active elements each having a first, a second and a third terminal, the first terminals of the elements being connected in common, a signal being applied to the second terminal of one of said pair of active elements, and means for supplying desired bias voltages to the second and third terminals of the pair of active elements;
  • a third active element having a first, a second and a third terminal, the current path between the first terminal and the third terminal through the third active element being connected between the first terminals of the pair of active elements and a common reference potential;
  • means for applying a direct current gating signal to said second terminal of said third active element said means including a mechanical switch and a direct current voltage source connected to the second terminal of said third active element;
  • envelope forming circuit means connected to the second terminal of said third active element for receiving said gating signal.
  • a gate circuit comprising:
  • each comprising a pair of transistors the emitter electrodes of which are connected in common and a third transistor having a collector connected to said emitter electrodes, said plurality of differential amplifier means being connected to said first voltage source in parallel;
  • a second voltage source for supplying a biasing voltage to the respective base electrodes of said third transistors through said switching means; and a time delay circuit means commonly connected to the base electrodes of said third transistors and through said switching means to said second voltage source, said time delay circuit means comprising a capacitor commonly connected to the base electrodes of said third transistors, a first diode commonly connected to the base electrodes of said third transistors so as to be forwardly biased by said second voltage source, a resistance connected to said first diode in series, and a fourth transistor connected to said resistance in series.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Electronic Switches (AREA)
  • Electrophonic Musical Instruments (AREA)
US5851A 1969-02-05 1970-01-26 Gate circuit for electronic musical instruments Expired - Lifetime US3656008A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP44008148A JPS4919213B1 (enrdf_load_stackoverflow) 1969-02-05 1969-02-05

Publications (1)

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US3656008A true US3656008A (en) 1972-04-11

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US5851A Expired - Lifetime US3656008A (en) 1969-02-05 1970-01-26 Gate circuit for electronic musical instruments

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US (1) US3656008A (enrdf_load_stackoverflow)
JP (1) JPS4919213B1 (enrdf_load_stackoverflow)
DE (1) DE2004835C3 (enrdf_load_stackoverflow)
FR (1) FR2033851A5 (enrdf_load_stackoverflow)
GB (1) GB1236535A (enrdf_load_stackoverflow)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3999149A (en) * 1975-06-20 1976-12-21 D. H. Baldwin Company Modulation system
US4052679A (en) * 1975-04-14 1977-10-04 Sanyo Electric Co., Ltd. Phase shifting circuit
US4173916A (en) * 1974-10-18 1979-11-13 Matsushita Electric Industrial Co., Ltd. Tone generator system for an electronic organ

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5279060U (enrdf_load_stackoverflow) * 1975-12-11 1977-06-13
DE2917352C2 (de) * 1979-04-28 1983-12-29 Dr. Rainer Böhm GmbH & Co KG, 4950 Minden Elektronische Orgel

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2233317A (en) * 1937-05-25 1941-02-25 Philco Radio & Television Corp Amplifier for television system
US3078395A (en) * 1960-04-04 1963-02-19 Rca Corp Bidirectional load current switching circuit
US3284713A (en) * 1963-03-26 1966-11-08 Motorola Inc Emitter coupled high frequency amplifier
US3288907A (en) * 1962-05-07 1966-11-29 Hammond Organ Co Electronic musical instrument with delayed vibrato
US3429976A (en) * 1966-05-11 1969-02-25 Electro Voice Electrical woodwind musical instrument having electronically produced sounds for accompaniment

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2233317A (en) * 1937-05-25 1941-02-25 Philco Radio & Television Corp Amplifier for television system
US3078395A (en) * 1960-04-04 1963-02-19 Rca Corp Bidirectional load current switching circuit
US3288907A (en) * 1962-05-07 1966-11-29 Hammond Organ Co Electronic musical instrument with delayed vibrato
US3284713A (en) * 1963-03-26 1966-11-08 Motorola Inc Emitter coupled high frequency amplifier
US3429976A (en) * 1966-05-11 1969-02-25 Electro Voice Electrical woodwind musical instrument having electronically produced sounds for accompaniment

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4173916A (en) * 1974-10-18 1979-11-13 Matsushita Electric Industrial Co., Ltd. Tone generator system for an electronic organ
US4052679A (en) * 1975-04-14 1977-10-04 Sanyo Electric Co., Ltd. Phase shifting circuit
US3999149A (en) * 1975-06-20 1976-12-21 D. H. Baldwin Company Modulation system

Also Published As

Publication number Publication date
DE2004835B2 (de) 1973-10-31
DE2004835A1 (de) 1970-08-20
DE2004835C3 (de) 1974-06-20
GB1236535A (en) 1971-06-23
FR2033851A5 (enrdf_load_stackoverflow) 1970-12-04
JPS4919213B1 (enrdf_load_stackoverflow) 1974-05-16

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