US1814849A - Amplifying system - Google Patents

Description

July 14, 1931. A. P. YOUNG ET AL 1,814,849

' AMPLIFYING SYSTEM Filed Aug. '7, 1928 Inventors;

Ar'th unPYoung, Joseph Hutt,Decea.sed,

Cecilia; Elizdbm X,

TH eh At'tbrneg.

Patented July 14, 1931 UNITED STATES PATENT OFFICE ARTHUR PRTMIROSLE YOUNG, OF KENILWORTH, ENGLAND, AND JOSEPH HUTT, DE-

CEASED, LATE OF KENIL-WORT'H,

ENGLAND, BY CECILIA ELIZABETH HUTT, EX-

ECUTRIX, OF KENILWORTH, ENGLAND, ASSIGNORS TO GENERAL ELECTRIC COM- PANY, A CORPORATION OF NEW YORK AMPLIFYING SYSTEM Application filed. August 7, 1928, Serial No. 298,057, and in Great Britain October 15, 1927.

Our invention relates to means for supplying a steady voltage for the operation of a thermionic valve amplifying or receiving system from a source, the voltage of which is subject to fluctuations. In particular, the invention is concerned with a thermionic valve amplifying system, which is adapted to supply operating currents for a sound reproducing device of the kind provided with an operating winding which is oscillated in a magnetic field, which is preferably of a steady Value.

T he object of the invention is to simplify the arrangements employed for supplying the necessary operating voltages to a thermionic valve amplifier or receiver used in conjunction with a sound reproducing device of the kind above specified.

In accordance with the invention, the steady voltages of different values which are necessary for the operation of a power amplifier, or a receiver embodying a power amplifier, are obtained from a source of variable voltage by connecting across the source reactors or choke coils shunted by condensers and connected in series with one another, any one or more of said reactors or choke coils also constituting the electromagnetic field system of a sound producing or reproducing device or devices. In order to adjust the excitation current flowing through the choke coils, a resistance is preferably connected in series'therewith, the value of which is such as to permit the desired excitation current to flow.

In order that the invention may be fully understood, reference is directed to the following description of the accompanying drawing showing diagrammatically an arrangement in accordance with the invention.

In the drawing isillustrated a power amplifier embodying two stages of valve amplification, V and V being connected in cascade with one another so that they form the first and second stages respectively. Anode current for the operation of these valves is supplied from a source S which may be a direct current supply main, or a source of rectified alternating current, either of which is subject to fluctuations in voltage, which it is gard to the operation of V choke coil 1 supplies only a part of the total voltage. Across chokes 1 and 2 are connected condensers 4 and 5 respectively, and the combination of chokes and condensers is found to absorb all undesired fluctuations in the voltage of the supply S, and, consequently the usual choke may be omitted from the lead to the supply. If desired, however, it may be included in the lead from the source to the anode of V although it is found possibleto dispense with the use of this choke coil, as the chokes and condensers 1, 4 and 2, 5 are found to provide sufficient smoothing effect.

In accordance with the invention, the

chokes 1 and 2 may constitute the electrov magnetic field system oftwo sound reproducing devices, or loud speakers, of the type having a moving coil located in a constant magnetic field, and supplied with the fluctuating currents corresponding with the sound waves to be reproduced. The chokes 1 and 2 may thus serve three purposes, viz, of providing the steady excitation current for the sound reproducers, to smooth out fluctuations in the supply voltage, and to give the necessary potentials for the operation of the anode circuits of the valves V V and are suitably designed with this .end in view. If only a single loud speaker is to be employed, the remaining choke will. of course, be constituted as an iron-cored choke of customary design. lVIore than two chokes may be employed, if necessary or desirable.

In order to adjust the excitation current to the desired value, we preferably insert a resistance 3 of a suitable value in series with the chokes 1 and 2, a milliammeter A being bodying thermionic valves,

also included for'indicating the excitation current flow.

The grid bias for the grids of the valves V V is provided by the battery 13 with the tappings as shown.

Fluctuating potentials which are to be amplified are applied through the input circuit A to the grid of valve V the output of V passing through the transformer T, and being applied to the grid of V The output of valve V is taken through the condenser 8 and the output transformer 9, whence it is applied to the moving coil of the sound reproducing device or devices, audiofrequency choke 7 being provided for preventing the audio-frequency currents from flowing back through the source S. If a large output current is desired, instead of the single valve V a plurality of valves in parallel may be employed, without otherwise affecting the design of the apparatus.

It will be noticed that in the arrangement described, the variation which is always to be expected in the plate current of the output or power valve or valves has a. negligible effect on the currents through the excitation coil of the sound reproducing device, which is consequently maintained always at approximately the correct value.

WVhat we claim as new and desire to secure by Letters Patent of the United States, is:

l. The combination with an amplifier emof current supply terminals, a series of reactors connected between said terminals, said reactors being adapted to draw a certain excitation current from said terminals and to smooth fluctuations in voltage at said terminals, and at least one of said reactors constituting an electromagnetic field system for a sound reproducer, current controlling means in series with said reactors for adjusting said excitation current, and anode circuits for said thermionic valves connected with said reactors at different points and separated electrically by at least one of said reactors whereby different operating potentials for said circuits are received from said reactors when the supply terminals are energized.

2. The combination with an amplifier em-: bodying thermionic valves, of anode circuitsfor, said valves, a capacitor connected in shunt with each of said circuits, anode "current supply terminals, a plurality of reactors connected in circuit between said terminals and said valves and arranged to provide a smoothing means for voltage fluctuations at said terminals, at least one of said reactors constituting an electromagnetic field for a sound reproducer, one of said reactors being adapted to supply a portion of the operating potentialrequired by one of said anode circuits, and all of the operating potential required by another of said anode circuits, said anode circuits being electrically separated by at least one of said reactors.

3. The combination with an amplifier embodying thermionic valves having anode circuits provided each with a shunt capacitor, and anode current supply terminals, of a plurality of reactors connected in circuit between said terminals and said valves and arranged to draw a certain excitation current from said terminals and to provide a smoothing means for voltage fluctuations at said terminals, at least one of said reactors constituting an electromagnetic field for a sound reproducer, means in circuit with said reactors for controlling the value of said excitation current and each of said reactors being adapted to supply at least a portion of the operating potential required by any one of said anode circuits and at least one of said reactors being interposed between said anode circuits, said reactors and said shunt capacitors providing the sole filter means between said terminals and said valves.

In witness whereof, we have hereunto set our hands this eleventh day of July, 1928.

ARTHUR PRIMROSE YOUNG. JOSEPH HUTT,

Deceased, By CECILIA ELIZABETTI HUTT,

Eweoutrz'w.

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