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Патент USA US2071739

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Feb. 23, 1937.
’
_ F. A. FISCHER
2,071,739
AMPLIFIER ARRANGEMENT FOR LISTENING DEVICES
Filed Sept. 26, 1935
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Patented Feb, 23, 193?
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2,071,739
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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.
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