US2848919A - Tone intensity envelope control for electrical musical instruments - Google Patents

Description

Aug. 26, 1958 J. M. HANERT 2,843,919

7 I TONE INTENSITY ENVELOPE CONTROL FOR ELECTRICAL MUSICAL INSTRUMENTS Filed May 29. 1953 PlANO SUSTANING PEDAL.

KNEE 56y CONTROL QPERATD WHENEVERANY PEDAL IO [5 DEPRESSED g 4 M H t .the tuning circuit.

tes Patent TONE INTENSITY ENVELOPE CONTROL FOR ELECTIRHCAL MUSICAL INSTRUIVIENTS John M. Hanert, Des Plaines, llL, assignor to Hammond Organ Company, a corporation of Delaware Application May 29, 1953, Serial No. 358,517

9 Claims. in. sit-1.26

al. Patent No. 2,480,132, granted August 30, 1949, which discloses a pedal-controlled instrument for use with a piano for producing percussive accompaniment bass tones. In the instrument shown in said patent, the initial intensity of the tones produced was determined by the velocity of pedal depression. Thus, when a loud tone was to be sounded, the player had to tap the pedal very sharply to obtain the necessary high velocity of pedal depression. This resulted in undesirable noise due to the contact of the sole of the players shoe with the pedal. Furthermore, the player had to acquire a new technique, that is, the ability to strike the pedals with the velocity required to obtain a tone of the desired intensity.

It is an object of the present invention to provide an intensity control which is not dependent upon the velocity of pedal depression but in which the desirable sharp attack and slow decay characteristics of the tonal envelope inherent in the instrument of said patent are retained.

A further object is to provide an improved intensity control for a pedal-operated accompaniment instrument which is elfective only when all pedals are released. In other words, the control is adjusted prior to the depression of a pedal and any changes in its position of adjustment while a pedal is depressed are ineffective to alter the percussive intensity envelope of the tone being pro,- duced.

Other objects will appear from the following description, reference being had to the accompanying drawing which is a block and schematic circuit diagram :of the instrument.

The instrument is played by twelve pedals 10 for an octave of notes in the bass register. Each of these pedals, except that for the note C, opens a switch 12 upon depression of the pedal. The switches 12 are connected in series in the tuning circuit of a push-pull oscillator 14,

the tuning circuit including an inductance L16, the terminals of which are respectively connected to the control grids of triodes13 and 19. The tuning circuit also includes one or more capacitors C20 connected in parallel across the terminals of the inductances L16, the number depending upon which of the pedals 10 is played. It will be noted that the capacitor C20 associated with the pedal 10 for the note B is at all times elfcctive in The values of the capacitors C20 are such that the oscillator 14 will be tuned to a frequency corresponding to the pitch of the operated pedal, and

when none of the pedals is operated will be tuned to the it open until another pedal 10 is operated, as shown in the aforesaid patent.

The oscillator 14 is of known construction and is mere- 1y representative of a large variety of well-known types of oscillators or other bass tone signal generators which could be used. The output of the oscillator 14 is supplied to a distorter 22 which may be of any well-known construction and may include a pair of triodes 23 which are biased so that only the positive peaks of their input signals are transmitted. The output signals are thus in the form of pulses which are rich in harmonic content. When converted into sound, this signal produces very desirable bass tones of quality similar to those of a rich piano bass tone sounded with its octave. The octave effect is obtained due to the use of an attenuating capacitor C23 in the output circuit of one of the triodes 23.

The output of distorter 22 is supplied to the control grid 24 of a control pentode 26 through a circuit including blocking capacitors C28 and C29 in series. The connection between these two capacitors is connected to a 58 v. terminal by a high value resistor R30 to prevent the build-up of static charges on these capacitors. The suppressor grid 32 is connected to the cathode 34, and the latter is connected to ground by a low value resistor R36. The plate 38 is connected to a source of plate voltage shown as a terminal +280 v. through a load resistor R40. The screen grid 42 has its potential determined by a voltage divider network connected between the +280 v. terminal and ground and including resistors R44, R46, and a potentiometer R48. The junction between resistors R44 and R46 is connected to the screen grid and the potentiometer R48 is adjusted so that a given voltage such as 58 v. on the control grid 24 will bias the pentode as closely as possible to cutolf. The pentode 26 is of the remote cutofi type such as a 6SK7 tube. The plate 38 is connected by conductor 50, capacitor C52, a minimum volume control potentiometer R54, and a capacitor CS6, to the control grid 58 of an amplifying triode 60. The potentiometer R54 is connected to ground through a resistor R62 in series therewith and is operated by a suitable volume control knob adjustable at will by the player of the instrument.

The triode 60 operates in the manner of a cathode follower, -or phase splitter and its output circuits are respectively coupled to control grids of power amplifying tetrodes 64, 65, the outputs of which are transformer coupled to a pair of speakers 68 connected in parallel.

A conductor 70 connects the control grid 24 of control pentode 26 with one terminal of a resistor R72, the other terminal of which is connected to ground through a capacitor C74 and to a 58 v. terminal through a resistor R78. Resistor R72 is also connected through a resistor R to a contact 82 of a single pole double throw switch having a movable contact arm 84. The switch arm 84 is connected to a -58 v. terminal through a resistor R86 and is connected to ground through a capacitor C88. The other switch contact 90, with which the switch arm 84 is normally in contact, is connected to ground through a conductor 92 and a resistor R94 constituting with R86 a part of a voltage dividing network determining the voltage to which the capacitor C88 is normally charged. Other parts of this network comprises a group of resistors R to R107, each of which has one terminal connected to conductor 92 and its other terminal connected to one of a group of switch contacts 110. The contacts are adapted to be engaged cumulatively in succession and make electrical contact with a contactor 112, diagrammatically illustrated as a curved blade pivoted at 114. An insulating handle lever is secured to the blade 112 and the blade and handle are normally urged clockwise by a suitably anchored coil spring 118. The blade 112 is connected to the movable contact of a potentiometer R122 which, in series with limiting resistors R124 and R125, is connected between ground and a 58 v. termi- 3 nal. The contact 120 will usually be adjusted to a position at which the potential is about 40 v.

The switch arm 84 is moved to its dotted line position by suitable mechanical means (for example, as disclosed in the aforesaid Patent No. 2,480,132) whenever any of the pedals is depressed, and is spring returned upon release of the pedal. Depression of any pedal also opens a switch 126 which is connected in series with a switch 128 and a resistor R130 between a 58 v. terminal and the switch contact 82. The switch 128 is opened by depression of the sustaining pedal 129 of the piano with which the instrument is being played.

In playing the instrument, the handle 116, which may be in position to be operated by the knee, is moved countterclockwise for increased loudness and permitted to be moved clockwise by spring 118 for decreased loudness.

The potentiometer R122 is normally not adjusted by the player and may be set by the manufacturer of the instrument at a value such that a reasonable minimum of intensity of sound is produced when the blade 112 is in contact with the contact 110 which is directly connected to the conductor 92. As the knee operated control handle 116 is moved clockwise or counterclockwise from an intermediate position, more or fewer of the resistors R100 to R107 will be effective to determine the voltage across capacitor C88.

The resistors R100 to R107 are of such values that as they are successively and cumulatively effective in the voltage divider circuit they will cause the intensity of the tones produced to decrease in logarithmic steps of loudness. In other words, their values are determined in a large part by the grid bias-plate current characteristics of the pentode 26.

The pentode 26 is normally biased to cutoff because its grid 24 is connected through conductor 70 and resistors R72 and R78 to a 58 v. terminal.

In addition to operating the switch arm 84, each pedal 10 upon depression opens a switch 126 one pole of which is connected to a 58 v. terminal and the other pole of which is connected to a switch 128 adapted to be opened whenever the sustaining pedal 129 of the piano is held down. A resistor 130 connects the switch 128 to resistor R80.

When any of the pedals 10 is depressed, it first operates to open its associated switch 12 and thus tune the oscillator 14 to the pitch of the note corresponding to the pedal, and thereafter to move switches 84 and 126 to their dotted line positions.

When switch 84 engages contact 82, a portion of the charge on capacitor C88 will be transferred to capacitors C74 and C29. Capacitor C88 has a value approximately twenty times as great as that of capacitor C74, and its "associated resistor R86 has a value approximately one twentieth as great as that of R78 so that the time constant of the mesh C88, R86, is approximately equal to that of the mesh C7 4, R78. Because the capacitor C88 is so much larger than the capacitor C74, the latter will be charged to the same voltage as that across C88 nearly instantly, the rate of charge being determined mainly by the low value resistor R80.

The charges across capacitors C74 and C88 are reduced by current flow through the resistor R72 and conductor 70 to capacitor C29 and to the control grid 24 of pentode 26. The values of the resistors and capacitors are such that the intensity envelope will be a curve having an initial concave slowly rising portion followed by a rapidly rising convex portion to a point of maximum intensity. Thereafter, the capacitors C74 and C88 will be discharged primarily through their associated resistors R78 and R86 so that the potential on the control grid 24 will decrease exponentially in the manner of the discharge curve of a capacitor in a circuit of substantial resistance.

In playing the instrument the knee operated lever 116 is swung back and forth to control the intensity of the tones produced. If any pedal is held depressed while moving of the lever 116 it will be clear that such movement of the lever cannot have any effect on the bias potential applied to the control grid of the control pentode because the switch arm 84 is not in engagement with contact 90. It will likewise be clear that movement of the lever 116 cannot have any eifect on the acoustic output while none of the pedals is depressed. In this respect, the lever 116 and voltage dividing network associated therewith function in an entirely different manner than conventional volume controls. It is only at the instant that a pedal is depressed that the position of the control lever 116 has any effect or significance. The control lever 116 and associated voltage dividing network is thus a means for predetermining the intensity of the tone to be produced upon the depression of any pedal. Thereafter, the intensity envelope of the tone sounded is determined by the time constant of the circuit which includes the following elements, R86, C88, switch 82-434, R80, R78, C74, R72, and C29. When the pedal is released the capacitor C74 is rapidly discharged through a relatively low resistance circuit including resistors R and R and switches 126 and 128. However, if the sustaining pedal 129 is depressed at the time that one of the pedals 10 is released this low resistance circuit for the discharge of the capacitor C74 is open. The intensity of the envelope of the tone will thus have a decay portion determined mainly by the time constant of the capacitor C74 and resistor R78. From the foregoing it will appear that irrespective of the position of the control lever 116 the intensity envelope of the tone produced upon depression of one of the pedals 10 will have an attack portion free from objectionable transients and a decay portion which will be long if the pedal is held depressed for a long period or if the sustaining pedal 129 of the piano is depressed before the pedal 10 is released.

Inasmuch as the values of a number of the components of the intensity envelope control circuit are of importance in obtaining the desired results, exemplary values of these components are set forth below, it being understood that most of these values are not critical and that substantial changes could be made in the values of many of the components without greatly affecting the results obtained, especially if compensating changes were made in the values of other components. The values given are under the assumption that the pentode 26 is of the 6SK7 type.

While I have shown and described a particular embodiment of my invention, it will be apparent to those skilled in the art that numerous modifications and variations may be made in the form of construction thereof, without departing from the more fundamental principles of the invention. I therefore desire, by the following claims, to include within the scope of my invention all such Similar talents played in conjunction with a piano having a sustaining pedal, the combination of a plurality of playing keys, tone signal generating means, an amplifier for the signals supplied by the generating means, said amplifier having a terminal the potential of which determines the amplitude of the output signal, an electroacoustic transducer connected to the output of the amplifier, means operable by the keys to determine the pitch of the tone signal supplied to the amplifier by the generating means, a potential source of such value that when applied to the terminal will cut oil the amplifier, a voltage source of such value that when applied to said terminal will cause the amplifier to amplify the tone signals to the maximum desired extent, a first capacitor connected between the said voltage source and said terminal, a first resistor connected between said potential source and said terminal, a single pole double throw switch biased so as to have its movable element normally engaging one contact thereof, means to apply an adjustable potential to said switch contact, a second resistor connecting the movable switch element-to said potential source, a second capacitor connecting said movable switch element to the voltage source, a conductor connecting the other contact of said switch to said terminal, and means for operating said switch against its bias upon operation of any of the playing keys.

2. The combination set forth in claim 1 in which the time constant of the first capacitor and first resistor is substantially the same as the time constant of the second capacitor and second resistor.

3. The combination set forth in claim 2 in which there is a switch operable by the sustaining pedal of the piano, in which said switch is connected between the terminal and the potential source, and in which means are provided to disconnect the sustaining pedal operated switch from the potential source whenever any of the playing keys is depressed.

4. In an electrical musical instrument having a control pentode having a control grid the bias on which determines the loudness of the tone to be produced, means for controlling the bias on said grid comprising a source of bias potential of such value that when applied to said grid will cause the pentode to be biased beyond cutoff, a pair of resistors in series connecting said source to the control grid, a capacitor connected between the junction of said resistors and a point of fixed potential substantially higher than that of said source, a third resistor and second capacitor connected in series between said point of fixed potential and said source, a voltage divider connected between said point of fixed potential and said source and having an output terminal, a control for adjusting said voltage divider to vary the voltage at said output terminal, a conductor including a switch connecting said terminal to the junction between said third resistor and second capacitor thereby to charge said second capacitor to a potential determined by the position of said control, and a circuit including said switch to connect said junction to said first capacitor.

5. In an electrical musical instrument having an output system including a terminal the potential of which determines the intensity of the tone produced, a first capacitor connected between said terminal and a point of fixed potential, a second capacitor of value much greater than that of the first capacitor, adjustable potential means for charging said second capacitor, resistance means respectively connecting said first and second capacitors to points of fixed potential of such value as to prevent transmission of signals through the output system when applied to said terminal, said capacitors and their respective resistance means having substantially the same time constants, and means operable by the player for dis connecting the second capacitor from its charging means and connecting it effectively in parallel with the first capacitor, whereby the first capacitor will have impressed across it a potential nearly as great as that of the initial potential of the second capacitor and the potential on the two capacitors will decrease at substantially the same rate to produce gradual decay in the intensity of the transmitted signal.

6. A tone intensity envelope control for an electrical musical instrument having an amplifier provided with a terminal the potential of which determines the amplitude of its output signal, tone signal generating means, a sustaining pedal, and playing keys for determining the pitch of the tone signals supplied by the generating means to the amplifier, the combination of a first mesh including a first capacitor connected to said terminal and normally applying a cutoff potential thereto, a second mesh including a second capacitor of value much greater than that of the first capacitor, said first and second meshes having substantially equal time constants, adjustable potential means normally connected to said second capacitor to maintain a potential upon the capacitor of such value that when applied to said terminal will cause the tone signals to be amplified, means operable by any of the playing keys to disconnect the second capacitor from the adjustable potential means and thereafter to connect the second capacitor to said terminal, and a low impedance circuit connected to said first capacitor for rapidly discharging the latter, said circuit including a switch operated upon depression of any of the playing keys and a switch operated upon depression of the sustaining pedal.

7. In an electrical musical instrument for producing musical tones having percussion tone intensity envelopes, the combination of a plurality of playing keys, tone signal generating means, a variable gain control device for the signals supplied by the generating means, said device having a terminal the potential of which determines the amplitude of the signal supplied to the output system, an electroacoustic transducer connected to the output of the amplifier, means operable by the keys to determine the pitch of the tone signal supplied to the amplifier by the generating means, an adjustable potential source, an expression control operable by the player during the course of rendering a musical selection to adjust the potential of said source, a capacitor, means normally connecting said capacitor to the adjustable potential source, and means operable upon operating any of the playing keys to disconnect said capacitor from said adjustable potential source and immediately thereafter to connect said capacitor to said amplifier terminal, whereby the intensity of the tone to be sounded is predetermined by the adjustment of said adjustable expression control.

8. In an electrical musical instrument for the production of tones having percussion intensity envelopes, the combination of a plurality of playing keys, tone signal generating means, a variable gain control device for the signals supplied by the generating means, said device having a terminal the potential of which determines the amplitude of its signal output, an electroacoustic transducer coupled to the output of the device, means operable by the keys to determine the pitch of the tone signal supplied to the amplifier by the generating means, a first capacitor, a second capacitor, the capacitance of said first capacitor being at least twice that of said second capacitor, a first resistor connecting said first capacitor to a point of fixed potential, a second resistor connecting said second capacitor to a point of fixed potential, the values of said resistors being proportioned so that the time constant of said first capacitor and resistor corresponds substantially to that of said second capacitor and resistor, a connection between said second capacitor and the terminal of said control device, means for charging said first capacitor to a potential of value such that when applied to said terminal will cause eflicient transmission of the signal, and key operated means for disconnecting said first capacitor from its charging means and to connect it to the second capacitor thereby to impress upon the said second capacitor a voltage substantially greater than half of that on the first capacitor at the instant that the latter is connected to the second capacitor, whereby the residual potential on said second capacitor plays a relatively unimportant role in the po' tential applied to the terminal of the control device upon quickly repeated operation of the keys.

9. In an electrical musical instrument, the combination of means for generating electrical tone signals of pitches corresponding to those of a musical scale, an output system, a plurality of depressible playing keys and means operable thereby to cause transmission from the generating system to the output system of a pitch related to the key which is depressed, an electro acoustical translating means forming part of the output system, an intensity envelope control means forming part of the output system, an expression control means adjustable by the player to predetermine the initial in- 20 tensity of the tone signals transmitted through the output system, and means operable upon depression of a playing key to transmit from the expression control means to the intensity envelope control means a setting corresponding to that of the position of the expression control means and at the same time to disconnect the expression control means from the intensity envelope control means, whereby the expression control means may be adjusted while a playing key is being held depressed and that upon release of the depressed playing key and upon depression of the same or another key the expression control means is effcctive to set said intensity envelope control means to cause initial intensity of a tone signal transmitted 'by the output system to be responsive to the previous setting of the expression control means.

References Cited in the file of this patent UNITED STATES PATENTS 2,276,390 Hanert Mar. 17, 1942 2,432,152 Hanert Dec. 9, 1947 2,482,548 Kerkhof Sept. 20, 1949

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