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Патент USA US2408244

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H, TOOMIM " ' . -
Filéd Dec. 30, 1944
2 Sheets-Sheet 1"
Attorney 5.
Sept; 24, 1946.
H_ mom
Filed Dec. 30, 1944
2 Sheets-Sheet 2
' FIG. 2,.
H5515"HfL TOO/‘#07
5; $2M”? I
' Patented Sept‘. 24, 1946 '
_ Hershel Toomim, Douglaston,‘ N.- Y., assignor, by
mesneassignments, to. Remco Electronicylne, '
lflewYork, Haida corporation of New York A
regenerating-December so, 1944, Serial No. 570,716 ,
(01.,179-1) I
Regenerative bass compensation. circuitsflsuch
as shown, for example in Shepard Patent No.
2,313,098, have been found to be practical and
efficient circuits for use inorder to drive a small
' of 3a, regenerative‘ and degenerative feed a back
between the‘screen grid and cathode of an audio
ampli?er, to produce a desirable bass boost char
acteristic, by the use of only, a minimum of addi
loudspeaker to. reproduce lowerfaudio frequen
tional elements.
cies. , Such a regenerative compensation circuit
' Another feature of my invention is the ‘combi
has the advantage that a volume compression ac
tion as well as almost any-desired degree of com
nation ,of a suitable humbucking or ?ltering
T .
It has heretofore been suggested that such re
means in such a circuit.
pensation may be readily securedby regeneration
over two stages of ampli?cation.
In the drawings, ,
, ,
_, g,
j Q
Figure 1 is a circuit diagramillustrating a pre
ferred embodiment of my invention;
7 ;
Figure _2 is‘ a series of curvesillustrating the
generative circuit be used in combination with
operation of the circuits of my invention; and -
degeneration derived from the voltage across the
Figure 3 is a circuit diagram illustrating possi
load impedance. This type of regeneration effec- '
tively reduces the impedance from which the ‘load ~15 ble modi?cations of my invention.
' :In Figure 1, an incoming radio frequency sig
works and therefore has va bene?cial damping
nal, which-maybe the intermediate frequency
Small radio receivers, of which the largestrvole _
. output of a heterodyne stage of a’ radio receiver,
is indicated, asrbeingr appliedto the terminals I‘, ,2
ume is sold, generally use two audio frequency
tubes, the ?rst of which :is a combination diode 20 at the left of’ the ?gure.‘ ,It will be understood
that this will be the'output of the last inter;
mediate frequency stage of a‘ superheterodyne
radio receiver which embodies my invention.
detector and triode ampli?er, and the other a
power output tube. , The combination of the re
generative anddegenerative feed backs. referred
to above has heretofore beenproposed in circuits , The incoming intermediate frequency signal is
adapted for use in such-sets.
such-use,-a pen 25 recti?ed in tube 3 in the diode recti?er which
comprises the anode 4 and cathode 5.- This is a
tode has been proposed for use as the ?rst audio
usuallrecti?er ‘circuit in accordance with stand
tube, following the detector; In such arcircuit,
ard practice. I 'An' A. V. ‘C. ‘voltage may be pro
aswshown in Figurev 5, of the Shepard: patent
duced [for use-linearly desired manner in accord-4
mentioned above, itis necessary. toiujse a sepa
rate stage of detection prior'torthe audio pentode 30 ancegwith usual practice. Also in accordance
withusual practice, the audio‘ frequency signal
stage in order to be able to use the grids of the
is applied through lead 8 and condenser ‘I to
pentode for the various feed back voltages. ' '
‘the ?rstjgridl? of thetube 3. This signal‘will
It has also been suggested to use a duplex'di
be ampli?ed in the tube sand supplied to the
ode pentode tube as the ?rst audio tube, as shown
in Figure 6, for example, of said Shepard patent. 35 power outputv tube 9 where it will be further am
pli?ed andtranslated in the loudspeaker.
This has, however, in circuits‘heretofore pro
' 'In-m‘y circuit I employa condenser C1 between
posed, involved the sacri?ce 'of a; considerable
the anode l3 ofthe .tube 3 and the grid I5 of the
. amount of power, actually in Figure 6 of said
.tube 9' which, as shown,'may have a preferred
Shepard patent,asacri?ce1of 501% of the power.
An object of'this invention is ;to'-provide a re
40 value of .004 microfarads in order to discrimi
generative bass compensation 'circuit'which com-.
bines the advantages of a degenerative feed back
as mentioned above, but‘ eliminates the vdisad
vantages of such combination.v By the use of my
invention I am able to employ a combination di 45
ode pentode tube as the ?rst audio tube of ,a radio
set having a power output tube, and ,avoid the
disadvantages referred to above. ‘ Iam also?able
to do this while providing excellent ‘?ltering, or
nate in favor of the higher frequencies. The _volt
ageapplied to the grid l5 will therefore have a
characteristic of amplitude with respect to fre
quency‘which is illustrated in curve A of Figure 2.
This voltage will, of course, vary the plate cur- ,
rentandydue to the resistances l8 and L9 in the
cathode leadof tube 9, the potential of the oath
ode will vary accordingly. ,A portion of the volt
ageacross the resistances I8 and I9 will be fed
some other means of hum reduction, which is 50 back, through the lead 20 to the cathode of tube
necessary, or at least highly desirable,,in ‘all bass
boost ,ampli?ers _-as the regenerative bastsiboost
makes the ‘ampli?er, highly susceptible topower
4; x
;g_ A feature of :myinventionisthe combination
3 in regenerative phase. Accordingly, these volt
ages; will be further ampli?ed in the tube 3, as
will beunderstood.
A dynamic loudspeaker 'of approximately 6
inches diameter‘willhave a resonance peak at
cessity of designing an intermediate frequency
ampli?er, around combination diode-pentode low
low audio frequencies and a second but lower
resonance peak at high audio frequencies. I con
nect the voice coil 2| of such a, loudspeaker
through leads 22 and 23 and condenser H in
gain tubes. It effects an increase in gain on the
order of 2 to 1 with tubes now available, as well
the circuit between screen grid 10 and ground to
as being more economical.
The use of the inverse speaker characteristic
to select a regeneration frequency may be accom
plished in other circuits, in which a triode or
other type tube is used in either or both cir
recognized as the resonance curve of such ‘a 10 cuits. One such circuit is shown in Figure 3 in
produce an effective voltage between the grid in
and cathode 5 in degenerative phase. The ef-.
fective voltage fed back from the loudspeaker
is indicated in Figure 2 by curve B, which will be
, V which both the regenerative and degenerative-feed
speaker turned upside down.
The ‘curves have been shown’ in this form for‘; backs are applied between the grid and cathode
of the tube 21. The operation of Figure 3 is
convenience of explanation. It will be understood
that the feedback represented ;by the-curve B is _ " otherwise substantially the same as that of Figure
actually a negative feedback and',‘therefore, might 1.5., 1, and will" be understood therefrom.
" iwhentriodesiare used, as shown in Figure 3,
be shown below the zero line. If it were so shown
the._sensitivity-to,power supply ripple is great
then the total effective feedback atiany _fre->
enough to require excellent ?ltering or some other
quency could be determined by simply adding
curves A and B.
Such an addition would show '
that, a maximum positive feedback occurs at fre
type of hum reduction.
Since neutralization is
20 difficult when the triode is used, I have shown,
in Figure 3, the use of a ?lter circuit which, by
quency F1 and again at frequency F5. It will be
employinga condenser 29, may be made resonant
understood that in thus transposing curve B to be
to the principal ripple frequency, and therefore,
below ‘the zero line, the left end of curve B as it
?lters this, frequency out to the. necessary extent
appears in the ?gure will coincide with zero and
the right end of curve B as it appears in the fig 25 at‘only a slight increase in cost.
'In'Figures l and 3 I have illustrated a portion
ure will also coincide with zero.
of the circuit in heavy black lines, which portion
Curve C of Figure 2 indicates the voltage at the
includes leads 22' and 23. from the voice coils
control grid 15 of the output tube 9 ‘due to .the
of the loudspeaker. It will be understood that in
combination of curves A and B. It will be noted
from Figure 2 that curves A and B cross at fre 30 feeding back a voltage from the voice coil inde
generative phase, this voltage may befedback by
quency f1 which will be a frequency of approx
applying it at any point in the circuits de?ned
imately 100 cycles. At or near this frequency
by these heavy black lines. Wherever it is ap
the effective voltage, due .to the combination of
plied in this circuit its effect will be the same
regeneration and degeneration, will have its max—
imum as indicated by'curve C. Therefore, the 35 qualitatively. Its quantitative effect will be dif
ferent, depending upon the impedance of the par
loudspeaker output will be given an effective bass
ticular speaker used. As a practical matter there
boost at approximately this frequency‘.
It may also be seen from Figure 2 that curves
, fore the point at which this voltage will be in
Band C again crosslat frequency is, which will
be approximately 4000 cycles. There will accord
ingly also be an accentuation of this frequency,
serted will be chosen in accordance with the im
pedance of a particular speaker it ‘is desired to
which is desirable as it gives the loudspeaker
characteristic the effect of crispness in repro
In. Figure 3 I have indicated, in broken lines,
a resistance 30 connected between the anodes of
ducing speech.
use with my circuit.
the .two tubes.
It will beunderstood that the regenerative
voltage will be smaller than the degenerative
voltage at all frequencies between the two speaker
resonance points. The overall effect will there
_ .
Such a resistance so connected
may beused to supply the degenerative feed back
voltage re?ected from the voice coil, in which
event the leads 22 and 23 will be .removed and
the ‘resistances I8 and [9 connected.
The im
pedance ofithe loudspeaker will bereflected back
in the pass band of the loudspeakerat which the 50 into the primarycoil connected to‘ the anode. of
the output tube and thus modify the voltage ap
overall effect will be degenerative.
pearing at this anode. This volt-age will be fed
In order to compensate for anode supply po
back through the resistance 30 to the anode of
tentials I provide condensers II and 25 and re
tube 21 and thereby be introduced into the re
sistance 26. 'Any hum potentials present will di
generative loop indicated by the heavy lines. The
vide between the condensers 24 and 25. These
voltage thus introduced will be introduced in
will be supplied to the grid 10 in phase to neu
degenerative phase so that the operation of the
tralize any potentials from the same sourc'eewhich
fore be regenerative except for frequencies with
circuit will be the same as before.
may be applied to the anode l3. By a suitable
It will be understood that while I have illus
choice of values for the condensers 24 and 25
the hum may be minimized to the extent neces 60 trated specific circuits and particular values, my
invention is capable of various modi?cations
which will be understood by those skilled in the
It will benoted that in my circuit I am using
art. I do not desire, therefore, to be restricted
the inverse speaker characteristic .to de?ne or
to the particular details shown and described, but
select a desired regeneration frequency, thereby
eliminating the necessity for using special fre 65 only within the scope ofthe appended claims.
It will, of course, be understood that conven
quency selective networks for such a purpose, and
tional systems of tone compensation, such as
therefore eliminating the necessity for circuit
elements that have previously been used in such
tapped volume controls, etc., may be used in com
bination with the circuits disclosed herein with
circuits, while improving the characteristics of
the circuits themselves. By applying all’ feed 70 the usual benefits.
back voltages to the screen of the pentode I also
What is claimed is:
make it possible to combine in such a tube a
1. An audio ampli?er circuit comprising an in
diode detector operating in the usual fashion.
put circuit, an audio ampli?er tube, and an out
This is highly desirable as it permits the. use of
put circuit, a transducer connected in said out
standard tubes now available, and. avoids the ne 75 put circuit, means for regeneratively feeding
back to said ampli?er a voltage having a char
acteristic which discriminates against fre
quencies lower than thelow frequency resonance
quencies higher than the low frequency resonance
point of said transducer, means for degenerative
recti?er circuit connected to the diode elements
of said ?rst tube whereby said radio frequency
voltage is recti?ed, means for applying said rec
ti?ed audio frequency voltage to the control grid
~ of said ?rst tube whereby it is ampli?ed there
in, a condenser connected between the anode of
ly feeding back to said ampli?er a voltage hav
said ?rst tube and the control grid of said sec
point of said transducer and in favor of fre
ing a characteristic which discriminates in favor ' ' ond tube, a pair of resistances connected in the I
of frequencies higher than the low frequency
cathode lead of said second tube, a connection
resonance point of said transducer, and means 10 from the midpoint of said resistances to the cath
ode of said ?rst tube, an output circuit connected
for deriving said second voltage from said trans
2. An audio ampli?er circuit comprising a pair
of ‘audio ampli?er tubes, a circuit which discrim
inates in favor of high frequencies connecting
the output of the ?rst tube .to the input of the
> to said second tube, a loudspeaker connected in
said output circuit, said loudspeaker having a
voice coil, a condenser connected .to the screen
grid of said ?rst tube, and a circuit connecting
said voice coil between said condenser and said
second tube, an output circuit for said second
8. An audio ampli?er circuit as de?ned in
tube, a transducer connected in said output cir
claim 7, in combination with means for compen
cuit, means for regeneratively applying a portion
of the current from the output of said second 20 sating anode supply potential variations.
9. An audio ampli?er circuit comprising a pair
tube to the input of said ?rst tube, and means
of ampli?er tubes, the ?rst of said tubes being a
for degeneratively applying a voltage derived
triode, a circuit which discriminates against low
from said transducer to the input of said ?rst
frequencies connecting the output of said ?rst '
tube, whereby the overall frequency, response
characteristic of said ampli?er circuit is a?ected 25 tube to the input of said second tube, means for
regeneratively supplying current from the out
by said transducer to produce a boost of low fre
quency response.
3. An audio ampli?er circuit as de?ned in
claim 2, in which the ?rst tube is a combination
diode pentode tube, and a detector circuit con
nected between the diode anode and the cathode
of said tube.
~ .
4. An audio ampli?er circuit as de?ned in
put of said second tube to the input of said ?rst 7
tube, an output circuit connected to said second
vtube, a. transducer connected in said output cir
cuit, and means for deriving a voltage from said
transducer and applying said voltage degenera
~ tively to the input circuit of said ?rst tube, where
.by the overall frequency response characteristic
claim 2, in which the ?rst tube has a plurality
of said audio ampli?er is affected by the imped
of grids including a screen grid and a cathode,v
and in which the feed back voltages are applied
ance characteristic of said transducer.
10. An audio ampli?er circuit as de?ned in
claim 2, in which the degenerative feed back volt
between said screen grid and cathode.
5. An audio ampli?er circuit as de?ned in
claim 2, in which the ?rst tube has a plurality
of grids including a screen grid and a control
grid, and in which the feed back voltages are
applied between the screen grid and ‘cathode and
no feed back is applied between the control grid
and cathode.
6. An audio ampli?er circuit as de?ned in
‘claim 2, in which the transducer. voltage is intro
duced into the circuit of the regenerated voltage.
age is derived from said transducer and supplied '
to said ?rst tube by means of a resistance con
nected between the anodes of said tubes.
11. An audio ampli?er circuit as de?ned in
claim 7, .in which said degenerative voltage isv
derived from said transducer and supplied to said
?rst tube by means of a resistance connected be
tween the anodes of said tubes.
12. An audio ampli?er circuit as de?ned in
claim 7, in combination with arecti?er and a
power recti?er circuit having a ?lter section res
7. An audio ampli?er circuit comprising a com
onant to the principal ripple frequency in the
bination diode-pentode ‘?rst ampli?er tube and a
power output tube, means for applying a radio 50 output of said recti?er.
frequency voltage to the diode of said ?rst tube, a
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