US2542017A - Combined electromagnetic piezoelectric phonograph translating device - Google Patents

Description

Feb. 20, 1951 2,542,017

A. H. ESTY El AL COMBINED ELECTROMAGNETIC PIEZOELECTRIC PHONOGRAPH TRANSLATING DEVICE Filed April 7, 1947 INVENTORST ALFRED M 57). JOSEPH A. DINSMORE.

W J/MW ATTORNE).

Patented Feb. 20, 1951 COMBINED ELECTROMAGNETIC PIEZO- ELECTRIC PHONOGRAPH TRAN SLAT- IN G DEVICE Alfred Houghton Esty, Sacramento, and Joseph Alvin Dinsmore, Santa Cruz, Calif., assignors of one-third to Charles Calif.

Grunsky, Santa Cruz,

Application April 7, 1947, Serial No. 7 39,940

13 Claims.

This invention relates to means for use in translating sound recordings into sound.

The physical difficulties of commercial recording necessitate that the bass be recorded on the record at a much lower volume (or voltage) or intensity than the treble, and the bass and treble are ordinarily played back from such a record at their recorded intensities. The reproduction of the sound is thus a distortion of the original.

It is desirable, for the sake of exact reproduction, to reproduce the bass and treble each at the same degree of loudness as in the original sound, or sometimes with the loudness of the bass and treble in controlled ratio other than that at Which the recordings indicate.

An object of this invention is to provide means to play back a commercial record so that the sounds heard are more like the original sounds than was heretofore possible. Objects of this invention also include the provision of a pickup which will play back such a record with the intensities of bass and treble in improved relationship or ratio to each other. Still another object of the invention is to provide means to adjust the bass voltage as played back, and thereby the audible bass intensity, and apply such adjustment more to lower than higher tones within the audible bass range.

Dampening appears to be universally necessary in prior pickup devices. It comprises soft plastic or similar material which presses against moving parts to eliminate or lessen resonant peak voltages. Without some dampening means, high peaks may occur in almost any part of the audible frequency range. Such peaks are occasioned by some resonant vibration corresponding to the frequency being generated, resulting in much higher voltages at such points. Dampening adds greatly to needle load, increasing record wear and loss of detail. The dampening effect is also variable with climatic conditions and age, due to variable characteristics of the dampening material itself.

Further objects of this invention are to avoid the necessity for dampening.

Still further objects of this invention will become apparent on understanding it.

Generally stated, the objects of this invention are accomplished by means of crystal and magnetic generators operated by the needle. The voltages generated thereby are controlled with relation to each other and translated into audible sound by any conventional or other device suitable for the purpose. What the listener then 2 hears is the combined sound of both, no matter whether the voltages of the crystal and magnetic generators are combined or added together and the resulting voltage converted into sound or each is converted individually into sound with both sounds being heard simultaneously.

These, as well as other features, of the invention, will be explained with reference to the accompanying drawings which illustrate the preferred exemplifications of the invention.

On such drawings:

Fig. 1 is a longitudinal section of a tone arm and appurtenant parts, partly in elevation.

Fig. 2 is a bottom plan view of Fig. 1.

Fig. 3 is an end elevation thereof.

Figs. 4 and 5 are cross sections on the lines 4-4 and 5-5, respectively, on Fig. 2.

Fig. 6 is a diagram of a circuit in which the novel pickup can be used.

Similarly to conventional pickups, the novel pickup of this invention comprises an arm II which carries the needle I2 which is to ride in the sound track on the record. The needle is attached to and carried by a shaft I 3, by means of a screw I4. The shaft I3 is mounted within synthetic rubber split ring bushings l6 and Ilia carried by the arm and forming front and rear bearings for the shaft. The bushings iii are held in place by a block I! which is attached to the arm H by screws I la.

The 'arm It carries a spool H], which in turn carries the windings of a coil I 9. Within the spool I8 is a soft magnetic iron split bushing 2| which serves as a housing for the rear bearing and also as part of the magnetic circuit of the coil. The shaft [3 carries an armature 22 which, preferably, is integral with the armature shaft [3 and is of suitable magnetic material. The armature 22 is preferably a fiat plate, at both sides of which are north and south magnetic pole pieces 23, 24, which are attached to the arm H by means of screws 26 and are in magnetic circuit with the bushing 2|. The armature shaft projects through and beyond the coil l8 and has a flat'rear end 21.

A crystal 28 is held against a downwardly projecting rib 29 on the arm H by a plate 3| which is attached to the arm by screws 32. The crystal device has the leads 33, 34. A clamp 36 attaches the flat rear end 27 to the crystal 28. It comprises jaw members 31, 38 which can be adjusted toward or away from each other by means of a screw 39, the head ll of which abuts against one of the jaw members while its threaded shank projects through or into a threaded opening in the other. Means are provided to adjust the effect of the mechanical movement of the needle l2 on the crystal 28, such means, preferably, comprising pads 42 of synthetic rubber or other resilient material interposed between end 21 of the jaw members of the clamp.

The pickup so far described can be used in a variety of circuits, the preferred circuit being shown in Fig. 6. A resistance 46 is in series with the crystal device 28, and a condenser 4! by-passes or is in parallel with the crystal device and the resistance. The resistance and condenser control the output of the crystal device. The coil l9 is in series with the resistance 46 and with the condenser 41. The free end of the coil I9 is to be connected to a terminal 48 of an amplifier (not shown) and another terminal 49 of the same stage of the amplifier is connected to the connection which is directly between the crystal device and the condenser.

' The mechanical movement of the needle, due to the sound track, is imparted to both the armature 22 and the crystal 28, causing each to generate voltages corresponding to such movement. Its effect on the crystal can be varied by the clamp screw 4!; tightening it causing greater stress on the crystal and causing it to produce and forward higher voltages, and vice versa. This can be done without necessarily varying the effect on the magnet and coil.

The crystal device is limited in the circuit so that it supplies only voltages of three hundred C. P. S. (cycles per second) and below. Therefore, when more (or less) voltage is generated by the crystal device it generates more (or less) bass voltage only. The circuit tapers the voltages generated by the crystal device so that at or near three hundred C. P. S., for example, the generated voltages become negligible while the voltages increase with decreasing C. P. S. to the lowest audible frequency. The point where the generated voltages become negligible will be varied according to the manner of recording adopted by the record manufacturer and which will normally lie somewhere between three hundred and one thousand C. P. S. The means included in the circuit which enables limitation of the crystal output is the resistance and condenser.

As already stated, by tightening the adjustment screw 39 more stress is placed on the crystal which causes it to generate more voltage and the crystal similarly will generate less voltage when such adjustment screw is loosened. It thus becomes possible to adjust the voltage generated by the crystal device while leaving the voltage generated by the magnetic device (the coil and the armature) practically constant. The voltages of the crystal and magnetic generating devices can thus be so regulated that they run completely flat at their overlapping point.

The armature shaft I3 is preferred to be very small, the needle of small diameter, and all other parts carried by such shaft are preferred to be very small. This reduces weight and results in low inertia which is important at high frequencies and high speeds.

By the use of this invention, the ratio of the volumes of different frequencies can be adjusted in playing back a record without necessarily changing the stiffness of the needle to any substantial degree and without any blanket change of volume of all frequencies reproduced. A record made with a bass volume, which is low in comparison to the treble, can thus be played back fiat. This increased stress is not accompanied by any substantial increase in stiffness of the needle or load. Needle load can thus be kept low which means low weight on pickup arms, the records last longer, very sharp detail in delicate passages, and better response on high frequencies. Dampening, which adds greatly to needle load, is avoided. Another advantage of this invention is that, although the gain is not as high as that of an uncorrected crystal unit, it is amply high enough to play without preamplificatic-n directly into any average radio or amplifier, including rrfost table sets, while at the same time it generates fiat voltage which does not have to be modified by use of networks to compensate for deficiencies. Furthermore, there is no vertical response, that is, surface noise, caused by the vertical irregularities in the record groove. Vertical response is inherent in crystal units and absent in properly constructed magnetic units. Surface noise, caused by vertical response, is always of high frequency character. The only portion of this invention that could possibly transmit such surface noise is the crystal device, but the output thereof is limited to a frequency value that is far below the frequency of any surface noise.

The magnetic portion of this invention responds only to the side vibrations of the record groove. Hence, this invention, producing uniform response at ten thousand (10,000) C. P. S. has less surface noise than a conventional crystal unit which responds, say, up to four thousand (4,000) O. P. S. but responds very little or not at all to higher frequencies. The bass portion of a commercial recording is recorded by an amplitude technique and the treble portion is recorded by a velocity technique. By nature, a crystal is an amplitude generator and a magnetic unit is a velocity generator. In this invention, each performs the task to which it is best suited in the combination. No harmonics of low frequencies are possible in the use of this invention. The low tones are delivered only through the crystal and even if the crystal generates harmonies having a frequency above its cutoff point (say three hundred (300) C. P. S), it can not deliver them.

Certain details have been illustrated or de' scribed for the purpose of explaining the invention. Some of'them can be varied, added to, or omitted without departing from the spirit of the invention, the scope of which is defined in the appended claims.

We claim:

1. A phonograph translating device comprising a tone arm, an armature shaft mounted for rotational movement on the arm, means to receive a needle in said shaft, a coil carried by the tone arm, magnetic pole pieces carried by the arm adjacent to the coil, an armature between the pole pieces carried by the shaft, said cell, pole pieces and armature comprising magnetic voltage generator means, a crystal voltage generator element carried by the arm, means connecting the shaft and crystal, said magnetic and crystal gen erators actuated simultaneously by movement of a needle disposed in said shaft, means to limit the voltage output of said crystal generator element to frequencies not substantially higher than one thousand cycles per second, output terminals, and an electric circuit connecting said crystal and magnetic generators and said output terminals in series with one another.

2. [A phonograph translating device according.

auger-v to claim 1 and wherein the means to limit the voltage output of the crystalcomprises resistance and capacity elements connected electrically to posed between the pole pieces carried by the shaft,

said coil, pole pieces and armature comprising a magnetic voltage generator, a crystal voltage generator element carried by the arm and connected to said shaft rearwardly of said armature, a needle carried by said shaft and disposed adjacent to said armature, said magnetic voltage generator and crystal simultaneously actuated to generate voltage upon movement of said needle, output terminals, and an electric circuit connecting said magnetic and crystal generators and said output terminals in series with one another.

4. A phonograph translating device according to claim 3 and provided with means to limit the frequencies transmitted by the crystal generator.

5. A phonograph translating device comprising a shaft arranged to carry a needle, a crystal voltage generator element and a magnetic voltage generator element to pick up diiferent ranges of frequencies, means comprising said shaft to connect said generator elements to a needle carried by said shaft whereby each of said generator elements is actuated generatively simultaneously upon movement of said needle, carried by said shaft, output terminals, and an electric circuit connecting said crystal and magnetic generators and said output terminals in series with one another.

6. A phonograph translating device according to claim 5 and wherein means is provided to limit the transmitting frequencies of said crystal element to not substantially higher than 1000 cycles per second.

7. A phonograph translating device comprising a needle, magnetic means to pick up treble, crystal means to pick up bass, said magnetic and crystal means being voltage generator means generatively responsive to movement of said needle, connections between the needle and both pickup means to actuate them simultaneously on operative movement of the needle, output terminals, and an electric circuit connecting said crystal and magnetic means and said output terminals in series with one another.

8. A phonograph translating device comprising an armature shaft arranged to receive a needle, a coil, magnetic pole pieces adjacent to the coil, an armature carried by the shaft between the pole pieces, said coil, pole pieces and armature comprising magnetic voltage generator means, a crystal voltage generator, means to connect the shaft and crystal, said magnetic and crystal voltage generators adapted to be actuated simultaneously by movement of the needle carried by the armature shaft, output terminals, and an electric circuit connecting said crystal and magnetic generators and said output terminals in series with one another.

9. A phonograph translating device comprising an armature shaft arranged to receive a needle, a coil, magnetic pole pieces adjacent to the coil, an armature carried by the shaft between the p'ole pieces, said coil, pole pieces and armature comprising magnetic voltage generator means, a fixed crystal voltage generator and a clamp connecting the shaft and crystal, said magnetic and crystal voltage generators adapted to be actuated simultaneously :by movement of a needle carried by the shaft, the clamp comprising means to vary the effect of movement of a said needle on the crystal, output terminals, a d an electric circuit connecting said crystal and magnetic generators and said output terminals in series with one another.

10. A phonograph translating device comprising an armature shaft arranged to carry a needle, a coil, magnetic pole pieces adjacent to the coil, an armature carried by the shaft between the pole pieces, said coil, pole pieces and armature comprising magnetic voltage generator means, a fixed crystal voltage generator, and a clamp connecting the shaft and crystal, said magnetic and crystal voltage generators arranged to be actuated simultaneously by movement of a needle carried by said shaft, the clamp comprising means to vary the effect of movement of a said needle on the crystal, and means to limit the crystal to transmitting frequencies not substantially higher than one thousand cycles per second comprising a condenser, output terminals, and an electric circuit connecting said crystal and magnetic generators and said output terminals in series with one another.

11. A phonograph translating device comprising a tone arm, an armature shaft mounted for rotational movement on the arm, a needle carried by the shaft, a coil carried by the tone arm, magnetic pole pieces carried by the arm adjacent to the coil, an armature between the pole pieces carried by the shaft, said coil, pole pieces and armature comprising magnetic voltage generator means, a crystal voltage generator element carried by the arm, means connecting the shaft and crystal, said magnetic and crystal generators arranged to be actuated simultaneously by movement of said needle, output terminals, and an electric circuit connecting said crystal and magnetic voltage generators and said output terminals in series with one another.

12. A phonograph translating device comprising an armature shaft arranged to carry a needle, a coil, magnetic pole pieces adjacent to the coil, an armature carried by the shaft between the pole pieces, said coil, pole pieces and armature comprising a magnetic voltage generator means, a fixed crystal voltage generator, means to connect the shaft and crystal, said magnetic and crystal generators arranged to be actuated simultaneously by movement of a needle carried by said shaft, means to limit the crystal voltage generator to transmitting frequencies not substantially higher than one thousand cycles per second comprising a condenser, output terminals, and an electric circuit connecting said magnetic and crystal generators and said output terminals in series with one another.

13. A phonograph translating device comprising a shaft arranged to carry a needle, magnetic voltage generator means to pick up treble, crystal voltage generator means to pick up bass, connections including said shaft to connect a needle carried by the shaft to both pickup means to actuate said pickup means simultaneously on operative movement of the needle carried by said shaft, means to limit the frequencies transmitted by the crystal comprising a condenser,

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Thorington Oct. 30, 1928 Number Number Number Name Date Thomas Sept. 19, 1933 Van Deventer Oct. 31, 1933 Tarkington Feb. 25, 1936 Dally Apr. 23, 1940 Dally Nov. 4, 1941 Williams Jan. 6, 1942 Bauer Aug. 14, 1945 FOREIGN PATENTS Country Date Great Britain July 5, 1938

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