US2211540A - Electrical musical instrument - Google Patents

Description

Aug. 13, 340. T. J. GEORGE I ELECTRICAL MUSICAL INSTRUMENT 4 Sheets-Sheet 1 Filed April 6, 1937 R. w W m 1 I M h uo m 3 35:; A W g E N L n. T2 I 2 a: a: P2, 2: M R

u I INVENTOR 94. i I BY gyms J. Mom

Au 13, 1940. ,TJ. GEORGE 23 9 ELECTRICAL MUSICAL INSTRUMENT Filed April 6, 1957 4 S nsets-Sheet 2 ZIO ATTORNEY.

Aug. 13, 1940. T. .1. GEORGE ELECT RICAL MUSICAL INSTRUMENT Filed April 6, 1937 4 Sheets-Sheet 3 INVE NTOR. BY 20mm d. 6EORQE.

ATTORNEY.

ug. 13; 1940- J. GEORGE 2,211,540

ELECTRI CAL MUS I CAL INS TRUMEN T Filed April 6, 1937 4 Sheets-Shet 4 c Q 3 I v) g g 5% 21 o: nu

1 L. o 2 g E Z i I 5 z a 01: f 9 3% 0: 2 a! wig} E O F CL Fol: I L1": Q

c: Q'gb I oLl-J n o IINVENTOR 2 THOMAS J. GEORGE ATTORNEY.

Patented Aug. 13, 1940 UNITED STATES PATENT OFFICE ELECTRIGAL MUSICAL INSTRUMENT Application April 6, 1937, Serial No. 135,285

3 Claims.

This instrument relates to electrical musical instruments of the type using various vacuum tubes and the like for attaining various sounds, tones and control thereof. The invention is concerned with improvements over the disclosures in similar devices, disclosed in such patents as Youngblut 2,045,172, Kock 2,046,463, Coupleux 1,980,911, Bethenod 1,789,032, Young 1,823,716, Hitchcock 1,877,316 and the like.

An object of the invention is to provide an improved arrangement of parts, whereby so called glow discharge tubes may be used to advantage.

Another object is to provide tuning means that may be readily coordinated to standard tunin forks or the like and permit said tuning forks to control the pitch or frequency of vacuum tube oscillators and glow discharge oscillators, thus making the oscillators as constant in frequency as the forks controlling them.

Another object is to provide certain simplifications and elimination of parts, and circuit arrangements as contrasted with prior art structures.

Another object is to keep all oscillators of difierent octaves, but of the same note, in perfect tune with each other at al times, and to provide means whereby they may be tuned simultaneously with a single tuning control.

These and other objectives are attained by the means described herein and disclosed in the ac-- companying drawings, in which:

Fig. 1 is a, diagrammatic representation of the electrical relationship of various parts comprehending one form of the invention.

Fig. 2 is a diagrammatic detailed drawing of a 0 regenerative tuning. fork oscillator, formrng'a de tail of the invention.

Fig. 3 is a .variation of the device shown in Fig. 2. I

Fig. 4 is a diagrammatic detailed drawing of glow discharge tube oscillators as used in a modified form of the invention.

Fig. 5 is a variation of the arrangement in Fig. 4. 1

Fig. 6 is a diagrammatic sketch showing generally the relationship of various parts of an instrument embodying the invention.

Fig. 7 is a diagrammatic drawing showing an arrangement of parts for producing a chime effect.

In Fig. 1, the parts represented are related in the following ways.

Visualizing the keyboard of an ordinary organ, piano, or similar-keyboard instrument, the individual keys are recognized as the means that a player contacts for initiating the creation of sound. In conjunction with Fig. 1, it is to be understood that as a player depresses a given key, he closes an electrical switch. Such switches are indicated at II, I3, I4, I5 and I6. It is to be understood that similar switches are provided, one for each key of the instrument. For the purpose of simplifying explanation of the invention, only a few of the various identical circuits are shown. Each key actuated switch controls a circuit through its own or associated oscillator, to the sound producing device such as an audio amplifier and loud speaker.

In Fig. 1, the oscillators, of which one is provided for each note to be produced by the instrument, incident to operation of the individual keys of the keyboard, may be considered in groups, each group comprising all of the same notes of the instrument, but each of the notes being in but one of the succeeding octaves. Three of the oscillators, of a group that may be designated the A, or A note group, are shown in Fig. 1. Each such note group comprises a master oscillator I! and one associated -or additional secondary or supplemental oscillator for each octave of the instrument. Accordingly, there are provided in the instrument, twelve note groups as C, Ct, D, Dt, E, F, Ft, G, Gt, A, All, and B, each comprising a master oscillator and associated supplemental or secondary oscillators. Fig. 1 shows only a master oscillator I1 and two secondary oscillators, I8 and I9. The master oscillator includes in its tuned frequency, the tuned frequencies of all of the secondary oscillators, in even divisible factors. For example, in Fig. l, the master oscillator, is, we will say, tuned to oscillate at 1760 c. p. s. (cycles per second) and will be considered as note A of the highest octave of the instrument. The first supplemental oscillator I8 is tuned to oscillateat 880 c. p. s. and thereby gives note A of the second highest octave of the instrument. Each next lower octave note A has an oscillation frequency of one-half that of the next higher octave note A. Thus oscillator I9 has a frequency of 440 c. p. s. and so on, determined by the number of octaves to be included inthe complete instrument. Each master oscillator controls all of its associated secondary or supplemental oscillators in this manner. The oscillator of the higher frequency controls the oscillator of the next lower frequency. Thus, master oscillator I'I controls oscillator I8. Oscillator I8 controls oscillator I9, etc.

The electrical energy used to actuate the oscillators is obtained from' a common power source for all the parts of the instrument, and is inditained from power. supply lines, to the desired directelectrical current to be used in the operation of the electrical musical instrument. As shown herein, the positive tap 2| of the power pack 20 is electrically connected with each of .the master oscillators in the manner in which master oscillator I1 is connected in Fig. 1, over common supply lead 21.

Each master oscillator includes a master tuning control means 23 which is a high resistance rheostat acting as a variable grid leak for effecting tuning. The lead 26, tapped on the group supply line 21, has connection, through resistance 28 with 1 the screen 29 of tetrode 30. Although in this case a tetrode is used, any multi-electrode tube could Screen 29 1 be used, such'as triode, pentode, etc.

is by-passedto ground through condenser 3| at 32 and also is connected with the grounded end of. inductance 33 and with the grounded side of I stabilizing condenser 35.

The anode or plate 36 of tetrode 39 is connected to supply line 21 through coupling resistance 31 and to one side of output condenser 38 and which condenser has its other side connected to control lead I50 and output potentiometer 39.

The grid 40 of tetrode 30 is connected to the is a. condenser, but which may be a resistance,

an inductance, a transformer, or any means for impressing some of the output voltage from oscillator [1, upon oscillator l8 for the purpose of 5 controlling the frequency of the secondary oscillator Hi. The secondary oscillator also has connection with group supply line 21 through resistance 46. Each succeeding secondary oscillator, such as I9 and such additional oscillators of a given note group, have similar connections with the group supply line 21 and a capacity such as 45 interposed between such succeeding oscillators in the same way as the capacity 41 is interposed between oscillators l8 and I9. Each of the secondary oscillators and-the connections thereof are alike except for being tuned to different frequencies as previously explained. Therefore an explanation of secondary oscillator l8 only will be given. The anode 48 of triode 56 is connected to resistance 46 and to one side of plate condenser 49.

70 53' is grounded. When switch I3 is closed manuallyby a specific key of the instrument, as previously explained, the output from oscillator I8 is fed fromplate 4B of triode '50 through condenser 49, through potentiometer 5| to resistance 75 56 and from there through closed switch l3 to bus bar 51. It may also pass through resistance 34 to the lower contact of switch l6 for closrre to bus bar 6| if switch I6 should be operated. The bus bar 51 is common to all upper switches of all finger operated keys,,and bus bar 6| is 5 common to all lower switches. It should be mentioned that the upper and lower switches associated with a given key, close to their respective bus bars 51 or 6| simultaneously, upon operation of the key. In this regard, it will be noted, 10

that the master oscillator also may have connection to bus bar 51, by way of switch I and potentiometer 39; and to bus bar 6|, through the lower contact of switch l3. This produces overtones, explained below. 15

Reverting now to triode 50, the cathode 59 thereof, is grounded and has connection with the tap on inductance 52. The inductance has connection at its one end with one side of'grid condenser 54. v 20 Attention is now called to the second bus bar 6|. The bus bar 6| 'is used for completing circuits for effecting overtones or harmonics. In other words, when playing in a given octave, it is possible to also play, at the same time, the 25 same notes in the next higher octave. The bus bar 51 consolidates all of the oscillations of the given octave, which may be termed the funda mental, and the bus bar 6| consolidates all of the oscillations of the overtones in the octaveabove. Suitable volume controls 62 and 63 are connected with the bus bars 51 and 6| and are connected through customary audio filters 64 and 65 and swell ped'alcontrol means 66. It will be seen that this arrangement provides a means of combining octaves, with results similar to the well known coupling arrangement of a pipe organ with this improvement, that by means of and plate condensers, by the size of the inductance used, and by the resistance of the variable grid 50 resistance. The coupling of the oscillators as shown herein, causes each next higher oscillator of each note group to 50 control and dominate the next lower oscillator, that master tuning is effective from the so called master oscillator of 55 each note group of oscillators. Thus, in Fig. 1, when oscillators I1, l8, and I9 have been tuned approximately to the frequencies noted, oscillator |1 will assume control and thereafter the final tuning of all oscillators in the A? group may be 0 effected simultaneously by variation of grid 'resistance 23. A twofold advantage thus results. All oscillators of the same note group are always perfectly in tune with one another. Also, slight retuning when necessary, may be efiected quickly, 65 by only one control, since all oscillators are tuned in one motion.

Fig. 2 shows an improved type of master oscillator. Here an ordinary tuning fork, I0 is used to control the frequency of oscillatiion of vacuum tube The grid of this tube is connected to coil l2 which is an iron core inductance so placed inv close proximity to one of the vibrating tines of the fork that an alternating voltage is set up in the coil and impressed upon the grid l3. .This

voltage is amplified in the plate circuit of the tube and the resulting plate current fluctuations in passing through another iron core inductance I4 which is placed in close proximity to the other tine of the fork, causes the fork to vibrate at its own natural period of vibration. Thus an alternating voltage having thefsame frequency as the fork is generated, which frequency does not depend upon the tube for its constancy, but upon the mechanical properties of the tuning fork. Thus a voltage of exceedingly constant frequency is available.

This oscillator can therefore be advantageously substituted for master oscillator I1 in Fig. 1. To do this, supply lead I5 in Fig. 2 is connected to lead 21 in Fig. 1. Potentiometer IS in Fig. 2 assumes the purpose of potentiometer 39 in Fig. 1 and output lead I19 connects to lead I52 in Fig. 1. The control lead is I59 in both figures.

With this change made, and with all secondary oscillators brought into tune with the master o:.cillator, all oscillators in the entire note group will be permanently in tune, with one another.

Reverting again to Fig. 1, at 61 is shown another oscillator which may be used to generate the very low frequencies, corresponding to the bass pedal notes of an organ.

Since the pedal board is arranged to be played with the feet, and since it is seldom necessary to play more than one pedal note at one time, an economy may be realized by letting one oscillator generate all notes of the pedal bass.

Triode 68 is arranged in an oscillating circuit with inductance 69, grid condenser 19, tuning condenser H and plate condenser 12. Output of theoscillator is controlled by potentiometer 13 over lead 14 to the swell control 66.

Each bass foot pedal controls a switch I14, 15, and 18. These switches are so wired in series that when all pedals (and switches) are normal, ground 11 is applied to grid 18, and the tube does not oscillate. If any pedal, as for example the A pedal, is operated, switch 16 is operated. The ground is removed from the grid, and the variable grid resistance is connected thereto, permitting :the tube to oscillate, at a frequency determined by the constants 69, 19, H, 12, the tube itself, and variable grid resistance 19. Control lead I59 from the lowest oscillator in the A note group is also connected to the grid of oscillator 61 through coupling condenser 89. If now resistance 19 is varied until the frequency of oscillation becomes approximately half the frequency of the lowest oscillator in note group A,

, theoscillator 91 will be drawn into exact tune with the note group, by virtue of the voltage impressed upon its grid through condenser 89 over control lead I59. In like manner, switches I14 and 15 when operated will permit oscillator 81 to be tuned by means of their associated resistances 8| and 82 and held in tune with the corresponding note groups over control leads 83 and .84.

Thus a single oscillator can be used to generate, for example, a full octave of bass notes, each note of which 'will always be in perfect tune with its associated note group.

Referring again to swell control 68, it will be seen that the lower end of the potentiometer 85 is connected to condenser 86, the other lead of which condenser is grounded. As the output lead 81 is moved from the high end of the resistance 85 toward the low end, the rate of attenuation of the high frequency voltages is virtually the same as for the low frequency voltages. If resistance 85 were grounded directly instead of connecting to condenser 86, the rate of attenuation for the low frequencies would be higher than that forthe high frequencies. The practical re-' sult of this arrangement is that for all volume levels, the bass and treble notes have the same relative output.

Lead 81 connects to the grid of special audio amplifier tube 88. This tube is of the so called super control type, having a remote cut-off bias feature. Its plate and screen are fed through suitable resistances from the common supply lead 21. The cathode is grounded. Grid coupling resistance 89 connects at one end to lead 81, and at the other end to by-pass condenser 99, and also to iron core choke 9I. The other side of choke 9| connects through resistance 92 and resistance 93 to direct current supply 94 which furnishes a negative potential for determining the normal operating grid bias for amplifier tube 88. The output voltage is fed through condenser 95 to audio amplifier 98 and to speaker 91 where the impulses are converted into sound.

At 98 and 99 are two vacuum tubes which together with their associated condensers, resistances and iron core inductance, are arranged to generate a sine wave oscillation of very low frequency, (a few cycles per second), Tube 98 receives its plate potential from the common supply line 21. Condenser I9I couples through grid resistance I92, the grid of tube 99 to the plate of tube 98. The plate of tube 99 receives its plate potential through resistance I93 from lead 21 and through condenser I94 is coupled to the grid of tube 98. Tube 98 drives tube 99 which in turn drives tube 98. Thus a continuous oscillation is maintained, and a sine wave voltage is built up across choke I95, condenser I96 and potentiometer I91. Through condenser I98 this slowly oscillating voltage is-superimposed upon the grid voltage from source 94 applied to the grid I99 of amplifier tube 88. Thus the grid bias on this tube slowly. fluctuates above and below the normal operating point. As a result the gain of the tube 88 increases and decreases at the same rate, as the oscillation of tubes 98 and 99, giving an apparent tremolo effect to the sound coming from the amplifier and speaker. By means of variations in the capacity of condenser I9I, the speed of fluctuations or tremolo may be varied to suit the player. Potentiometer I91 permits adjustment of the degree of tremolo.

At H9 is a rectifier tube arranged with its associated equipment, to permit the simulation of a chime, bell, piano, or any similar musical percussion instrument. At H4 is a resistance connected to supply lead 21, through which condenser-I12 is maintained in a charged condition. When switch H3 is closed, the charge on this condenser is.applied to. the primary winding of transformer I II. A pulse of induced voltage is built up in the secondary winding of transformer III which, is rectified by tube H9 and applied across variable resistance 92 and condenser II5 with polarity as marked, positive at the cathode of tube II9 connected to the upper end of resistance 92 and negative at the lower end of this" selectively operable switches, the switches and oscillator being normally inoperative, a variable tuning means for each switch, said switches when operated singly, adapting the oscillator to oscillate at a frequency approximately determined by the variable tuning means associated with the selected switch, a master control means for each switch, said master control means generating freouencies harmonically related to but differing from the frequencies generated by said oscil latcr the frequency 0! the oscillator being exactly determined by the master control means con- .nected to the selected switch whereby to permit the generation, one at a time, of a plurality of exactly predetermined frequencies by one oscillater, said oscillator generating a single frequency only at one time.

2. In an electrical musical instrument having a plurality of sources of signals of the difierent frequencies of the musical scale, having a plurality of key controlled switch means and having an output system including electro-acoustic translating means; the combination of an oscillator, means rendered operative by said switch means to tune said oscillator closely but not exactly toa frequency determined by the operated switch means, and means for simultaneously impressing upon said oscillator a signal from one of said sources having a frequency which is harmonically related to but diners from that of the note determined by the onerated switch means.

3. In an electrical musical instrument oi the type having a keyboard, a plurality of sources oi electrical frequencies corresponding to some oi the notes or the musical scale and having a means for translating into sound signals selected by the operation oi said keys; the combination vof a single oscillator for supplying signals oi a plurality of different frequencies bearing harmonin relationship to some of the frequencies supplied by said sources, means under the control of said keys for tuning said oscillator to a frequency closely corresponding to the note represented by the operated key, and means controlled by said key for impressing upon acidoscillator a signal from one oi said sources having a frequency which is harmonically related to but diners from that represented by the operated key, said frequency from said selected source being impressed upon said oscillator to'determine the exact frequency oi oscillatlon'therecf.

THOMAS J. GlilORGliL Aug. 13, 1940. P.-KOLLSMAN 2,211,543

REMOTE SPEED INDICATOR Filed Jan. 28, 1937 3 Sheets-Sheet 1 INVENTOR FHUL KEJLLSNFIN ATTORNEI

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