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Патент USA US2098370

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Nov. 9, 1937.
AUTOMATIC CONTROL
H. BARTELS
OF AMPLIFICATION
'
Filed 061;. 28, 1935
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INVENTOR.
BY
' 2M5 BARTELS
7%. WV
ATTORNEY.
Patented Nov. 9, 1937
2,098,370 ~
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"
: Signor to 'Ielefl'rnken, Gesellschafti?irfnrahh' i'r"
’
-
b.
his}?
,gof ampli?ers
.
we;
on
' phy, teIephonyQsound
tum-mem
andreprodjic
ing, radio broadcasting and the ,like,y_.and
alargeShumber of persons [used
f_for;.the
‘ pjto a switching-pin period of
approximately"50 1:660 in sec., no distortions
for ‘whatsoever,_were_, discemihle. However. it was
.its principal object the
improved
apparatus and methodlof',operationr’wherebylthe
~ampli?cation
.in
expanded
the volume
or. compressed
.ratiofjof
of the trans‘mittedlsignal.§,..
-'such:_-_.apparatus_
._ -;
z ‘
glve?od b!
.
these tests‘ over a longer
e. thesejperiodsb'ecame
essentially
..
shorter'sincej’the', observers became more atten~
"tIvetO'the’dIstui'banceS."
.
_
.
.AdditionaLtests werefcarried outwith pure
toneslwhe'nebyiéa-bumer tone of '800 cycles '10
'uuntypnereyqL-jmeym- "
1O , Such apparatus
ume of orchestral
orthe like 'tendslto‘eb “per 'secondKBOWHz)" was, supplied to the input
_ ceed the capacity of the apparatus oritheicapacity of‘the. ampli?er,‘ and during a short period of
of the record,- traci; on whichthey signal, is .re ' time a second buzaersound of 1000 Hz was added
by
of,:thej,afore-mentionedswitching ar
varies betweenlglOOO the latter
have to be _.rangement;ir_isuch a‘jmanner that the amplitude
reduced to 1:50 for makingrecordqplates. l-This . of‘ the fundamental‘ oscillation was‘ thereby not
, corded. Ii foriinstanoe the naturalmsignallevel
,. . O:
value.
‘determined by. r-thejeshblisheslémpve
.chang'ed. .
15
out with this
fjarrangement p'roy'ed’the conditions ‘to be essen
.Of
distance
the “West.
and the
{mill-‘69535;
noise Jevek‘
5115311414"?
'Weioadest
$81.18, -.t.°. ‘Put vtially,,wor'segj‘lili'eadyat a building-up period of
the ‘disturbing action
through the matrix between the 81PQVi=5n=~-;W Lapprdiimately'f2f0fm'
20 thermore, the steepness ofhtheeut-soundjgroove‘ _' of the arti?cially
non-linear distortion
‘non-linear distortions are
should not __become- too greatqat. largeyolume. _ was noticeable.
‘since in this'casetheplate
nollonger be : oftenfei‘icounteredin practice v(at ordinary excess
played without objectionable ‘Zidistortio'n. The control of. an ampli?er, pick-up, sound-recorder
conditionsv are still less“ favorable in casezof the and the like, the second harmonics often appears 25
25 talking ?lm where it isneo'essary inyiew of the ' withhigh amplitude), it is' of particular impor
tance to so dimension the control circuit that the
noise of the ?lm to reduce thera'nge of ampli?
cation to an, essentiallygreaterfextent thanfin _. buildingéup period will be less than 20 m sec.
the case of record plates.
'
.2
"
__ H Such short building-up periods as have not
It has been determined. that forjcontrolling ‘ been used hithertofor automatic volume control
30 the ampli?cation range automatically without arrangements, ‘are not only necessary for record
plate recording arrangements for physiological
disturbance or distortion‘, such transmission ar
rangements for transmitting orchestra perform Yreasons,‘ but also for purely technical reasons.
Thus if the building-up period'is assumed to be
ances, for instance, require extremely short build
,
.
_ ing up periods for ampli?cation control; The
100 m sec., and'a very loud tone of for instance
dying out periods may be 10‘to 20 times as long
as the building-up periods. For dimensioning
50 Hz should be, recorded suddenly, this signi?es
the required time constant for the control the
30
that 100 m sec. will have to pass before the con—
trol action begins. _However, during 100 :11 sec.
already 10 alternations of the tone of v50 Hz have
following points are of importance:
Upon a sudden transition from the softest to passed so thatat maximum the band oi the rec 40
40 the loudest parts, there always occurs ence'ssive ‘.ord plate between two grooves has been broken
control to a greater or less degree, especially in .through IOtimes. “Hence the record is useless.
sound recording arrangements. These and other At a building-up period of v20 m sec. only the
disturbances are avoided if the building-up pe
?rst half wave has practically been recorded ‘into
_ riod is less than twenty thousan'dths of a second the adjacent grooverwhereas the second alterna
(20 m sec). This fact has been ascertained in ' tion has been already controlled and in all prob
such manner that record plates especially selected
as to the most favorable performance have been
pli?er.‘ By means of a mechanically controlled
ability the band between the grooves of the rec
ord plate will no longer be destroyed. It will be
apparent from the foregoing that in ‘order to
eifectively ‘prevent cutting it through the band 50
placed in parallel to the loudspeaker, and in this
between the grooves at more than one point, the
volume control should respond within a time of
played through a loudspeaker and across an am
50 switching arrangement a detector ‘has "been
55
45
way very high and non-linear distortions were p the same order'of magnitude as the time of
vibration of the sound waves to be recorded, and
produced. The building-up period of this. de
tector was varied between 5 and 500 111 sec‘ It preferably should respond in a time of one~half 55
2
2,098,370
t of the time of a sound wave in order to prevent
" the other half wave from over-cutting.
In con?ict with the requirement of providing
short time constants in the control arrangements,
is the demand of noiseless performance. To
smoothen the performance it is necessary to use
?lter elements of comparatively large dimensions.
However, such ?lter elements introduce a large
time constant into the control arrangement.
10 Hence ?lter elements of smaller dimensions
should be used whereby, however, only insu?lcient
?ltering can be obtained. The appearing disturb
ing voltages are then to be eliminated in a differ
ent manner. In accordance with the present in
15 vention this is accomplished in that the control
elements are applied to the ampli?er in the form
of a bridging circuit. With this bridging circuit
the upper harmonics appearing due tolnsu?lcient
?ltering as well as other disturbing voltages are
prevented from passing into the useful circuit.
To avoid unsymmetrical conditions among the
elements forming the bridging circuit the one or
the other one of the elements is rendered adjust
able.
The invention will be better understood from
the following description when considered in con
nection with the accompanying drawing, and its
scope will be pointed out in the appended claims.
Referring to the drawing:
Fig. 1 is a wiring diagram of an apparatus
which operates on the straight part of its charac
teristic operating curve at high current to reduce
the ampli?cation ratio, and
Fig. 2 is a wiring diagram which operates simi
larly to reduce the ampli?cation ratio.
Fig. 1 illustrates one form of the invention in
which non-linear resistances in the form of dry
It is
obvious that the said recti?ers may also be re
‘ recti?ers are utilized as control devices.
40 placed by other non-linear resistances or by tubes,
in which case the circuit is to be adapted to the
changed operating conditions. The impulses
transmitted from the generator I through a re
sistance 2 are branched of! and supplied to an
45 auxiliary recti?er 3 which, in connection with the
capacity 4 and resistor 5, provides an adjusting
direct potential dependent upon the mean ampli
?cation level or signal volume for the control rec
ti?ers 6 and ‘I connected across the ampli?cation
channel. The resistor 8 forming a bridge circuit
50
together with the control recti?ers 6 and ‘l is
divided into approximately equal parts by the tap
at 9 for the purpose of forming the bridge, so that
the points l0 and I I have the same potential rela~
tive
to the potentiallat the points l2 and I3. A
55
biasing source 14 is provided so as to enable ad
justment to the proper working point of the cur
rent-voltage characteristic of the control recti
?ers which is important for the dynamic control.
The tap 9 of the resistor 8 is preferably made
60
adjustable to compensate unsymmetrical condi
tions of the individual elements of the bridge
such as unequalities of the rectifier resistances.
Obviously, the resistor 8 may be substituted by
65 two separate variable resistors.
In reducing the ampli?cation ratio, the ar
rangement of Fig. 1 has the advantage that at
high amperages it operates on the straight part
of the detector characteristic. If high potentials
70 are produced at the points l2 and i3 due to large
volume, it happens, as canbe readily seen from
the known detector characteristic, that the re
sistance of the detectors 6 and ‘I i. e. the resist
ance of the bridge between the points l0 and II
75 will be decreased.
In order to have the same advantages with an
increase of the ampli?cation ratio, the circuit 0!
Fig. 2 may be utilized. As in the embodiment of
the example according to Fig. 1, the control im
pulses are branched off from the input circuit and
are applied to the arrangement 3, 6, 5 and I4
which furnishes the displacement or control po
tential. The detected impulses are applied at
points 20 and 2| of the bridge circuit 22, the latter
consisting of detectors 23, 24 and resistor 25 with
tap 2B. In order that at large volume the ar
rangement operates on the straight part of the
detector characteristic, the ampli?cation train is
bridged by a resistor 21.
At high amplitudes of the alternating potential 15
the resistance of the detector bridge becomes low.
Consequently the voltage drop through the re
.sistor 21 ‘will be increased. As in the circuit ac
cording to Fig. 1, also at increase in dynamic at
higher amplitudes of the alternating potential, 20
the resistance of the detector bridge will be de
creased. In other words, the straight part of the
characteristic of the detectors is utilizedin both cases.
In the two examples the alternating potential
required for the production of the displacement
potential is derived ahead of the control member.
Obviously this potential can also be tapped in
back of the control device. The dimensioning oi
the individual members of the arrangement of the
auxiliary detector should then be altered corre
spondingly.
In case where the branched-off con
trol impulses should prove to be too low, suitable
amplifying means can be placed at an appropriate
place in front of or in back of, the control detector
3. In view of the control curves, the resistance
of the detector is to be high as compared with
the bridge resistance (8 and 25). Eventually, it
may be useful to place in parallel to the detectors
preferably variable resistorsthus providing means
of influencing the characteristic of the detectors.
What is claimed is:
1. An ampli?cation ratio control device in
cluding a bridge element comprising a resistor
and a pair of recti?ers, a pair of terminals 45
connected to said bridge element respectively at
a point between said recti?ers and to an inter
mediate terminal of said resistor, and means op
erable to apply to the end terminals of said
resistor a potential which varies as the volume
of the signal supplied to said terminals.
2. An ampli?cation ratio control device in
cluding a bridge element comprising a resistor
and a pair of recti?ers, a pair of terminals
connected to said bridge element respectively at 55
a point between said recti?ers and to an inter
mediate terminal of said resistor, and means
including a recti?er connected to a resistor
through a potential source for applying to the
end terminals of said resistor a potential which
varies as the volume of the signal supplied to
said terminals.
3. An ampli?cation ratio control device in
cluding a bridge element comprising a resistor
and a pair of recti?ers, a pair of terminals con
nected to said bridge element respectively at a
point between said recti?ers and to an inter
mediate terminal of said resistor, and means
including a recti?er connected to a resistor
through a potential source for applying to the T.
end terminals of said resistor a potential which
varies in a time of not more than twenty one—
thousandths of a second as the volume of the
signal supplied to said terminals.
4. An ampli?cation ratio control device in
18
3
2,098,370
cluding a bridge element comprising a resistor
and a pair‘ of recti?ers, a pair of terminals con
nected to said bridge element respectively at a
point between said recti?ers and to an inter~
mediate terminal of said resistor, and means
operable to apply to'the end terminals of said
and a pair of recti?ers, a’ pair of terminals
connected to said bri e element respectively
at a point between sai recti?ers and to an
intermediate terminal of said resistor, and means
including a recti?er connected to a resistor
through a potential source for applying to the
end terminals of said resistor a potential which
varies as the volume of the signal supplied to
said terminals and with a building up time of
not more than twenty one-thousandths of a 10
second.
8. An ampli?cation ratio control device in
cluding a bridge element comprising a resistor
and a pair of recti?ers, a pair of terminals con
resistor a potential which varies in a time of
the same order of magnitude as the time of a
sound wave as the volume of the signal supplied
10 to said terminals.
5. An ampli?cation ratio control device in
cluding a bridge element comprising a resistor
and a pair of recti?ers, a pair of terminals
connected to said bridge element respectively at
15 a point between said recti?ers and to an inter " nected to said bridge element respectively at
mediate terminal 01 said resistor, and means a point between said recti?ers and to an inter
including a recti?er _connected to a resistor mediate terminal of said resistor, and means
through a potential source for applying to the operable to apply to the end terminals of said
end terminals of said resistor a potential which resistor a potential which varies as the volume
varies in a time of the same order of magnitude
of the signal supplied to said terminals and
as the time of a sound wave as the volume of
with a building up time of the order of the time
the signal supplied to said terminals.
of a single sound vibration.
6. An ampli?cation ratio control device in
9. An ampli?cation ratib control device in
cluding a bridge element comprising a resistor cluding a bridge element comprising a resistor
and a pair of recti?ers, a pair of terminals con
and a pair of recti?ers, a pair of terminals con
nected to said bridge element respectively at a nected to said bridge elementrespectively at a
point between said recti?ers and to an inter
point between said recti?ers and to an inter
mediate terminal of said resistor, and means op
mediate terminal of said resistor, and means in
erable to apply to the end terminals of said cluding a recti?er connected to a resistor through
30 resistor a potential which varies as the volume
-a potential source for applying to the end ter
of the signal supplied to said terminals and with minals of said resistor a potential which varies
a building up time of not more than twenty as the volume of the signal supplied to said
one-thousandths of a second.
terminals and with a building up time of the
7. An ampli?cation ratio control device in
order of the time of a single sound vibration.
36
cluding a bridge element comprising a resistor
_
HANS BARTELS.
15
20
25
30
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