Патент USA US2071739код для вставки
Feb. 23, 1937. ’ _ F. A. FISCHER 2,071,739 AMPLIFIER ARRANGEMENT FOR LISTENING DEVICES Filed Sept. 26, 1935 £.g8isw Féw lhmw g MN Mm. / . v23 . INVENTQ'R #1. aka. JA'JA o RNEY> Patented Feb, 23, 193? ‘ it, 2,071,739 A -, it ARRANGEMENT non LISTENING navrcss Fritz Alexander Fischer, Kiel, Germany, assignor to 'Electroacustic Gesellschaft mit beschrank ter Hattung, Kiel, Germany, a ?rm Application September 26, 1935, Serial No. 42,261 in Germany (letober 29, 193d “3 Claims. (01. 177-386) still use an individual ampli?er tube or tubes for My invention relates to an ‘ampli?er arrange ment for listening devices for air and submarine sound reception, in which groups of electro mechanical receivers for the sound are provided, 5 and by which the sound is converted into .elec tric energy, and in which further electric com pensators are provided to compensate for the time each sound receiver, while the amplifying device which is located between the compensator and the telephone may be common to all sound re ceivers. Any disadvantage which the individual 5 provision of a small ampli?er for each sound re ceiver may have is compensated by a considerable lowering of the noise level in the telephone due to the compensator noises, and is further com pensated by the advantage that the preliminary m ampli?ers between the individual sound receivers , lag which occurs through the different instances of time at which each of the individual receivers 10 encounters the sound wave. In such arrangements usually the receivers are and the compensator constitute non-reactive couplings if ampli?er tubes with negatively biased connected in series with the compensator and in series with the latter is connected an ampli?er which ampli?es the combined energy of all re 15 ceivers which is delivered by the compensator, and to the output of this ampli?er is connected the sound indicator which has usually the form of a telephone. With such an arrangement of the ampli?er the noises produced by the contact slides 20 of the compensator are ampli?ed to the same extent to which the received sound is ampli?ed. grid are used. My invention is illustrated in the accompany- 15 ing drawing in which-— This disadvantage might be avoided by placing the ampli?er between the compensator and the sound receivers, instead of placing it between the electro-mechanical impulse translators, shortly 25 25 compensator and the sound indicator. Such an arrangement is shown for instance in Figs. 4 and called hereinafter electro-mechanical receivers which are suitably electrically connected in a manner shown for instance in the aforemen 6 of the United States patent to Fritz Lange No. 1,971,688. The disadvantage of this arrangement , tioned Lange patent. Each of these receivers is is, however, that a complete ampli?er arrange connected to the compensator K by means of a so 35’ ment must be provided between each sound re ceiver and the compensator. preliminary ampli?er indicated in Fig. 1 by d, e, 2’, respectively. The compensator is connected by Since usually for each‘ receiver a number of thermionic tubes are used, and since usually in such a receiving ar way of the main ampli?er g to the sound indicator h, which may for instance be a telephone. It will be noted that the main ampli?er g ampli?es the 35 entire energy delivered by the compensator k, and rangement quite a'number of sound receivers are 35 employed, the a number of amplifying devices would have to be increased to such an extent that 'the- entire receiving arrangement is considerably complicated and rendered impractical. a Fig. 1 shows schematically the relative loca tions of the electro-mechanical impulse trans: lators or sound receivers, the preliminary amplie ?ers, the compensator, the main ampli?er and go the aural receiver; and Fig. 2 shows in detail the wiring arrangement of a preliminary ampli?er for one sound receiver. Referring ?rst to Fig. 1, a, b, c constitute the ‘ It is the object of my invention to provide a which constitutes the compensated combined‘en ergy of all receivers a, b, d. In single chain compensators such as are shown in the Lange patent aforementioned all 40 sound receivers are connected to a single chainv 40 compromise between the two above-mentioned which chain is closed at one of its ends by means methods of amplifying by which it becomes pos sible to have the bene?t of the advantages of the of a non-inductive resistance which is equal to the preliminary ampli?cation of the sound energy‘ wave resistance of the chain, while the other ' before it reaches the compensator without having chain end is connected to the ampli?er, whose 45 input impedance must likewise be made equal 45 the disadvantages of an ampli?cation which oc curs entirely between the compensator and the sound indicator. This compromise resides in di viding the ampli?cation so that one or several 50 steps vof a preliminary ampli?er are placed be tween the sound receivers and the compensator and the remainder of the amplifying ‘devices is, disposed betweenthe compensator and the sound indicator, such as a telephone. It is, of course, 55 necessary for the preliminary ampli?cation to to the wave resistance of the chain. Now-in» order that none of the sound receivers may form a point of re?ection for the energy of the other receivers, which-travels on the chain, each re- 50 ceiver must be balanced with respect to the chain so that its impedance, viewed from the com pensator chain is large with respect to the wave resistance of the chain; Experiments have shown that it is suillcient to make the receiver imped- 55 2 2,071,739 ~ance when measured with respect to the chain, six times the wave resistance of the chain, , If we consider this value, however, from the view ’ point of the receivers, it means that each re ceiver is closed'by the chain with one-sixth of its inner resistance. It-is, of course, entirely im material in such a case whether the receiver itself, ‘for instance by suitably dimensioning its winding, is provided with such a resistance value, 10 or ‘whether the above required balancing ratio is accomplished by interposing a suitable trans former. With such an arrangement the re ceivers viewed from the standpoint of e?iciency always operate with a considerable short-cir 15 cuit. Only one-seventh of the electro-motive force of the receiver is supplied to the chain as the chain voltage. This loss in voltage through lack of proper balance may be avoided, however, arrangements and for a receiver resistance of the order of 100 ohms, transformers with a step-up ratio of about 1:75. On this possibility 'above all rests the great importance of the preliminary ampli?cation. _ ‘. It is unfortunately not possible to utilize to the fullest extent the ampli?cation of the preliminary ampli?er tubes, because with such ‘an arrange ment the tubes are here short-circuited to a certain degree in a manner similar in which in 10 the arrangement without preliminary ampli?ers the receivers operate with a partial short-circuit, as described hereinabove. Since the anode load resistance is equal to one-sixth of the inner tube resistance, the voltage ampli?cation of the tube 15 equals D.7 by interposing between each electro-mechanical 20 receiver and the compensator chain a coupling element which is free from reaction, and which connects the receiver through a resistance, which is large compared with the inner resistance of the receiver. An ampli?er tube with negatively 25 biased grid constitutes such a ‘coupling element. Since such a tube constitutes a practically in?nite resistance, the entire electro-motive force of the receiver may be brought into effect. If desired this electro-motive ,force may be considerably 30 increased by the inter-position of a transformer. The ratio of the transformer is limited solely by the capacity of its secondary winding which eventually would short-circuit the highest fre quencies of the frequency range to be transmitted. 35 Such an arrangement in which negatively biased ampli?ers areused is shown in Fig. 2. In this ?gure the general arrangement, so far as the principle of preliminary ampli?cation and - main ampli?cation is concerned is the same as 40 that schematically shown in Fig. 1.. In Fig. 2, a, b, c again represent the electro-mechanical impulse translators, or electro-mechanical re ceivers. Each of these receivers is provided with a preliminary amplifying device through which the energy delivered by it is transmitted to the compensator K. In this ?gure the details of this preliminary ampli?cation are shown only with respect to the receiver 17. “The receiver is con nected by Way of a step-up transformer tr, to a 50 thermionic ampli?er tube e, the output side of which is connected to the compensator chain. The input side of this tube is connected to the secondary winding of transformer tr, a biasing voltage source i being provided in this circuit 55 by which the grid of the tube is negatively biased. The‘ output of the compensator which represents the'combined energy of all receivers, a, b, c is connected to the main ampli?er g‘, the output side of which latter is connected to the tele 60 phonevh. ‘ ' In case of low-ohmic electro-mechanical re~ ceivers, for instance in case of electro-magnetlc or magneto-strictiVe receivers, it is not necessary to place these preliminary ampli?ers into the 65 immediate vicinity of the receivers, such as must be done in case of crystal receivers, which can be built only with a high-ohmic resistance. It is, therefore, of advantage to build these receivers with an inherently low-ohmic resistance and to 70 connect these receivers directly into the lines which lead to the compensator and to locate the preliminary ampli?ers in the vicinity of the com pensator. It is still possible to construct for submarine sound receiving devices and at a fre quency of from 500 to 3,000 employed in such wherein D represents the effective anode reac 20 tion. It is, therefore, necessary to select an am pli?er tube which has the smallest possible effec tive anode reaction. The limit in the selection of the anode reaction is determined by the require ment that the inner resistance which is in 25 versely proportional to the effective anode re action must not become too great, since it is not possible to make the no-load impedance of the transformer in?nitely high. Therefore, tubes having too great an inner resistance are alone 30 for this reason ill-?tted for this purpose. I claim:-— ' 1. In a sound listening device having a plu rality of electro-mechanical receivers for receiv-' ing the sound energy and for translating it into 35 electric energy, an electric compensator and a sound indicator, all connected in series, the method of amplifying the received sound energy, consisting of preliminarily individually ampli fying the sound energy delivered by each receiver 40 before it reaches the compensator and ?nally amplifying the combined energy of all receivers delivered by the compensator before it reaches the sound indicator, the total amount of ampli? cation being divided between the preliminary and 45 the ?nal ampli?cation in such proportion that the noise level in the indicator, due to the ampli ?cation of the compensator noises, remains be low a disturbing magnitude. 2. In a sound listening device having a plu 50 rality of electro-mechanical receivers for receiv ing the sound energy and for translating it into electric energy, an electric compensator and a sound indicator, both connected in series, a pre 55 liminary thermionic tube ampli?er for each sound receiver, having a negative grid bias, and being connected between the receiver andsaid compen sator, and a main ampli?er, connected between the compensator and the indicator, for ?nally amplifying the combined energy of all receivers 60 before it reaches the sound indicator, the total amount of ampli?cation being divided between the preliminary and the ?nal ampli?cation in such proportion that the noise level/in the in dicator, due to the ampli?cation of the compen 65 sator noises, remains below a disturbing magni tude. 3. In a sound listening device having a plu rality of electro-mechanical receivers for receiv ing the sound energy and for translating it into 70 electric energy, an electric compensator and a sound indicator, both connected in series, a pre liminary thermionic tube ampli?er for each sound receiver, having a negative grid bias, and being 75 2,071,739 connected between the receiver and said compen , sator, and a step-up transformer between each receiver and its preliminary ampli?er, and a main ampli?er, connected between the compensator and the indicator, for ?nally amplifying the com bined energy ofv all receivers before it reaches the sound indicator, the total amount of ampli?ca 3 tion being divided between_the preliminary and the ?nal ampli?cation in such proportion that the noise level in the indicator, due to the ampli ?cation of the compensator noises, remains be low a disturbing magnitude. FRITZ ALEXANDER FISCHER.