US 3194870 A
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Description (OCR text may contain errors)
y 13, 1955 A. w. TONDREAU ETAL 3,194,870
SELF-CONTAINED ELECTRICAL MUSICAL INSTRUMENT Filed Jan. 15, 1962 3 Sheets-Sheet 1 m w o O Qynnem/om ALBERT W. TONDREAU LEON F. GEYER y WILLIAM A. TROTTO W/KM Mam
y 13, 1965 A. w. TONDREAU ETAL 3,194,870
SELF-CONTAINED ELECTRICAL MUSICAL INSTRUMENT Filed Jan. 15. 1962 3 Sheets-Sheet 2 Jammie 14 ALBERT W. TONDREAU LEON F. GEYER 4 WILLIAM A. TROTTO July 13, 1965 A. W. TONDREAU I ETAL SELF-CONTAINED ELECTRICAL MUSICAL IfiSTRUMENT Filed Jan. 15. 1962 (i Sheets-Sheet 3 J WILLIAM A. TRO'ITO United States Patent Office 3,194,870 Patented July 13, 1965 This invention relates to an electrical musical instrument, and particularly to self-contained types of stringed musical instruments, such as guitars, banjos, and the like.
The use of magnetic pickup or detecting elements for stringed instruments, such as guitars, banjos, violins, etc.,
in which the detecting elements feed amplifiers and loudspeakers energized from the normal electrical house supply, is well known. When using such amplifying devices, an electrical cord extends from the instrument to the amplifier and from the amplifier to the house supply, the amplifier being positioned in any suitable place on a stage or platform. It is obvious that the instrument cord will hamper and interfere with the movements of the musician and limit his maneuverability. Furthermore, the amplifier and loudspeaker, which are generally a single unit, are placed away from the musician, and particularly so if it is required that the musician be near a microphone for a vocal rendition. There is, thus, a discrepancy between the position of the source of the sound in the speaker and the position of the musician which is'unnatural.
The present invention is a self-contained electrical musi-' cal instrument which permits the musician to move about freely since there is no more of a limiting factor in the niusicians movements than there would be with a nonelectrical musical instrument. Since the instrument is self-contained, it is realized it must have the normal pickup units and house the amplifier, speakers, and power supply. Since the speakers and pickup units are attached to the same instrument, insulation has been provided to prevent feedback. Also, a pair of pickup units are provided, either of which may be connected to the amplifier, or both of which may be connected simultaneously to provide special tonal effects. In addition, a microphone input is provided so that the musician may render a vocal selection while being free to move about the stage or platform. Individual volume controls for each of the pickup units and the microphone permit a very flexible control of the tonal effects, volume, and combination of voice and strings.
The principal object of the invention, therefore, is to provide a self-contained electrical musical instrument.
Another object of the invention is to provide an electriwith the accompanying drawings, in which: n t FIG. 1 is a plan view of a guitar embodying the inven tion;
FIG. 2 is a cross-sectional view taken along the line 22 of FIG. 1;
FIG. 3 is a bottom view of the guitar shown in FIGS. 1 and 2 with the bottom plate removed; and
FIG. 4 is a schematic diagram of the electrical circuit embodied in the invention. Referring, now, to the drawings in which the same reference numerals refer to the same elements, the guitar shown in the drawings is composed of three sections, a
side section 5, a similar side section 6, and a central section 7, the latter section being rectangular in general form and on which is mounted a finger board 10 with an end 11 with its tuning keys 19. Also on this section is a bridge 12, a string anchor 15, an electro-magnetic vibration pick up unit 13near the bridge 12, and a second electro-magnetic pickup 14 near the finger board 10. Within the central section is a transistor amplifier 16 having the circuit shown in FIG. 5 and a power supply 17 of the rechargeable, sealed nickel-cadmium type supplying a voltage of approximately 11 volts. The amplifier is mounted on the central section by four screws such as shown at 18. The battery 17 is mounted on a riser 23 which is attached to a U-shaped frame 22 of the central section 7 by screws 24. The battery 17 is detachably held by spring clips 25, a plug 26 being connected to the battery 17 when a power switch 60 is oil". (See FIG. 4.) The central section is provided with an insulation 30 of any suitable type, such as felt or Celotex.
The two side sections 5 and 6 are of similar construc- 2 tion, the outer portions having curved side panels 32 and 33, respective bottom panels 132 and 133, and respective top panels 134 and 135. The material of these panels may be of wood, metal, tormica, or the like. The side, bottom and top panels are cemented to curved frame members 34 and 35 of aluminum or other suitable material, which are quare in cross-section and between which are spaced posts such as shown at 39. The side sections 5 and 6 are attached to the central portion 7 by six bolt and nut combinations holding aluminum angles 137 and138 to the side sections, one of which is shown in cross-section at and the others at 41. A pair of gibs 142 and 143 areattached by suitable screws 1 to angles 138 and 140 to permit a sliding door 144 to provide access to the amplifier 16 and battery 17. As mentioned above, suitable insulation 30, such as felt, Celotex, or similar material as shown in FIG. 2, separates the frame U-shaped member 22 from the side sections 5 and 6, and is attached by gluing or cementing to the interior surfaces of the side sections 5 and 6. Theend plates 37 and 38, which aid in holding side sections 5 and 6 to central section 7, are insulated from the central section 7 as shown at 36. Each side section has attached to the inner surface thereof acoustic absorbing material 42 and 43, such as Celotex.
Two loudspeakers 45 and 46 are positioned in the large ends of the side sections and are attached to the front surfaces of the respective sections 134 and by bolts, such as'shown at 47 and 48, layers of insulation 49 and 50 being positioned between the rims of the speakers and the respective front panels. Openings 52 and 53 are covered by any suitable material, such as a wire cloth mesh 51, which permits the sound to be emitted from the speakers. Openings 54 and 55 in the smaller ends of the side sections and also covered by a wire mesh 56 provide communication between the respective speakers and the free atmosphere to permit diaphragm breathing.
On the front of the guitar are four controls, such as a power switch60, a pickup selector switch 61, a potentiometer 62 for controlling the volume from pickup unit 13, and a potentiometer 63 for controlling the volume 'from'pickup unit 14. As shown in FIG. 4, the connecting switches for the pickup units 13 and 14 are interconnected, as shown by the dotted line, so that in the position shown in FIG. 4, both pickup units are connected'to the input of the amplifier, while the right-hand position of the switches connects only pickup unit 14 to theamplifier, and the left-hand position of the switches connects only pickup unit 13 to the amplifier. A greater amount of harmonics is detectable by the pickup unit meters 62 and 63 are at their zero positions.
.3 13, since it is positioned near the bridge 12, while more of the basic frequencies are detectable by the pickup unit 1.4. Any desired balance of tonal effects is, therefore, obtainable by manipulation of the potentiometers 62 and 63 when both pickup units are connected to the amplifier.
Located along the side of section is a potentiometer control button 65 and a microphone input jack 66 which may be connected to the amplifier with or without the magnetic pickup units 13 and 14 when the potentio- Thus, the musician has complete control of the output from his strings and the volume of his voice or other voices during the playing of the instrument. The microphone may be attached to the guitar.
As mentioned above, the invention is particularly free of feedback by eliminating electrical, mechanical, and acoustical coupling, the circuit shown in FIG. 4 aiding in preventing this feedback. Referring, now, to FIG. 4, the amplifier comprises the single voltage amplifier transistor 68 and two pushpull stages comprising transistors 69 and 70 for a low power stage and transistors 7'1 and 72 for a high power output stage, the output feeding the loudspeakers 45 and 46 in series over a transformer '75. The series connected speakers permit matching of im pedances between transformer and speakers, the speakers being properly phased as shown by the polarity indications.
The input to the transistor 68 is over loading resistor 77 and voltage divider resistors 78 and '79 and coupling condenser 81. A resistor 82 is connected between the base and collector of transistor 68. The remainder of the circuit is the standard type including a transformer '83 and a transformer 84, bias resistor 86 and filter resis- 94 are used in the second stage of the amplifier. Bias resistors 91 and 92, filter resistor 93, and filter condenser 94 are used in the second stage of the amplifier. Bias resistors 96 and 97, a thermistor resistor 98, a filter resistor 99, and a filter condenser 100 are used in the high power stage of the amplifier. Since this circuit has been specially designed to provide the minimum of feedback or electrical coupling between the magnetic pickup units 13 and 14 and the microphone, a typical operative circuit has the following values for the elements shown in FIG. 4.
The three potentiometer units 62, 63, 65 and fixed resistor 77 have a resistance of 10,000 ohms, condenser 81, a capacitance of 50 microfarads, resistor 79, a resistance of 4700 ohms, resistor 86, a resistance of 330 ohms, resistor 78, a resistance of 1500 ohms, and resistor 87, a resistance of 2700 ohms. Condensers 88 and 89 have capacitances of 50 microfarads each. For the second stage, resistor 91 has a resistance of 33 ohms, resistor 92, a resistance of 1200 ohms, resistor 93, a resistance of 220 ohms, and condenser 94 a capacitance of 50 microfarads. In the last stage, resistor 96 is 7 ohms, resistor 97 is 100 ohms, resistor 99 is 150 ohms, thermistor 93 is 100 ohms, and condenser 100 is 50 microfarads. A peak current of 150 mils is obtainable for operation of the amplifier with a model 9V0 battery of the type mentioned above. This circuit and battery will function continuously for four hours or more.
The above instrument, therefore, is completely selfcontained since it houses the electrical amplifier, power supply, and speakers, which, through the three-section construction of the instrument itself, the positioning of the amplifier and power supply within the central sec tion of the instrument and the speakers in opposite sides, not only is a mechanically and acoustically balanced instrument provided but one which eliminates electrical feedback when operated in the proper manner.
1. A self-contained electrical musical instrument comprising three sections, two of said sections being side sections and the third section being a central section having a rectangular cross-section to which the side sections are attached, said central section supporting the finger board and tuning keys of said instrument, at least one magnetic pickup unit positioned under the strings of said instrument, an amplifier in said central section, connections from said pickup unit to said amplifier, a potentiometer for controlling the transmission between said pickup unit and said amplifier, speakers in said sections, connections between said speakers and said amplifier, a power supply connected to said amplifier and positioned in said central section, and insulation surrounding the wall of said side sections and said central section.
2. A self-contained electrical musical instrument in accordance with claim 1 in which said speakers are positioned in the large ends of said side sections of said instrument, openings being provided in said side sections at the other ends of said instrument for interconnecting the back of said speakers with the free atmosphere.
3. Aself-contained electrical musical instrument in ac cordance with claim 1 in which a pair of magnetic pickup units are provided under said strings, together with a switch for interconnecting said pickup units to said amplifier and means for independently varying the volume of either of said pickup units.
4. A self-contained electrical musical instrument in accordance With claim 3 in which a microphone input is provided on said instrument, said input being connected to said amplifier.
5. A self-contained electrical musical instrument having a shell, a finger board, tuning keys and strings, said shell comprising three sections, two of said sections being side sections and the third section being a central section having a rectangular cross-section to which said side sections, said finger board and said strings are attached, a loudspeaker in each of said side sections, a pair of openings in said side sections adjacent said speakers, a second pair of openings in said side sections communicating with said speakers, an amplifier mounted in said central section,
' a power supply mounted in said central section, said power supply being connected to said amplifier and said amplifier being connected to said speakers, pickup units mounted on said central section and connected to said amplifier, and means for varying the input from said pickup units to said amplifier.
6. A self-contained electrical musical instrument in accordance with claim 5 in which an additional input to said amplifier is provided for voice signals.
7. A self-contained electrical musical instrument in accordance with claim 5 in which a multiple switch is provided between said pickup units and said amplifier, said switch being adapted to connect said pickup units to said amplifier, and means for independently varying the volume of signals from each of said pickup units to said amplifier.
3. A musical instrument having strings, the vibrations thereof being adapted to be detected, electrically amplified and reproduced, said instrument comprising a shell having a plurality of sections, a finger board, tuning keys, and at least one vibration pickup mounted on one of said sections, a sound reproducer within another of said sections, of said shell, an electrical amplifier and electrical power supply within said first-mentioned section, means for interconnecting said vibration pickup to said amplifier, said means including a volume control, means for connecting said amplifier to said sound reproducer, and means for connecting said power supply in said first-mentioned section to said amplifier.
9. A musical instrument in accordance with claim 8 in which said electrical power supply is a rechargable battery positioned within said first-mentioned section.
10. A musical instrument having strings, the vibrations thereof being adapted to be detected, electrically arnplia fied and reproduced, said instrument comprising a shell having a plurallty of sections, a finger board, tuning keys, and at least one vibration pickup mounted on one of said sections, a sound reproducer within another of said sections of said shell, an electrical amplifier and electrical power supply Within said first-mentioned section, means for interconnecting said vibration pickup to said amplifier, said means including a volume control, means for connecting said amplifier to said sound reproducer, a pair of vibration pickups on said first-mentioned section and a pair of sound reproducers, one within eachof two other sections of said shell, being provided.
11. A musical instrument in accordance with claim in which a pair of openings is provided in each respective section of said shell housing a sound reproducer therein and a switch for connecting said pickup units to said amplifier.
12. A stringed electrical musical instrument adapted to have the string vibrations thereof detected, amplified and reproduced within the instrument, power for said amplification being provided within said instrument comprising a sectionalized shell for containing different elements for reproducing the vibrations of said strings, a battery, an amplifier, said battery and amplifier being located in a centralized section of said shell, an electrical-to-sound wave transducer in a rear section of said shell, and a string vibration pickup located on said centralized section of said shell, the positioning of said battery and amplifier in said shell with respect to said transducer providing balance to said instrument when transported by a player during the playing of said instrument.
References Cited by the Examiner UNITED STATES PATENTS 2,288,463 6/42 Kislingbury 841.16 2,784,631 3/57 Fender 84-115 3,035,472 5/62 Freeman 84l.15 X 3,073,202 1/63 Evans 84-114 -32 relied on).
Radio and Television News, April 1955 (page 67 relied on).
ARTHUR GAUSS, Primary Examiner.