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Патент USA US2122207

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June 28, 1938.
E, w_ KELLQGG
2,122,207
RECORDING AND REPRODUCTION OF SOUND
Filed May 24, 1935
'
BY
/ .) Jury-0V
‘(2'
'
ATTORNEY
_
M22267
Patented June 28, 1938
UNE'H'EB STATES PATENT @FFEQE
2,122,207
RECORDING AND REPRODUCTION OF
I
SOUN
D
Edward W. Kellogg, Moorestown, N. J., assignor
to Radio Corporation of America, a corpora
tion of Delaware
Application May 24, 1935, Serial No. 23,167
30 Claims.
vThis invention relates to means for limiting
curvature in sound records of the groove type,
and has for its principal object the provision
of an improved apparatus and method. of opera
5 tion whereby excessive groove curvature of the
record is prevented.
As pointed out in a copending application of
Alda V. Bedford, Serial No. 8,292, ?led February
26, 1935 and assigned to the same assignee as
10 the present application, there is a Well recognized
limit to the higher frequency amplitudes that
may be satisfactorily reproduced. Among the
factors which determine this limit is the radius
of curvature of the tip of the reproducing stylus,
which must be small relative to that of the sharp
est curves in the record groove in order to pre
vent serious distortion. Recording at high gen
eral level is advantageous because it renders the
background noise due to imperfections in the sur
face of the record, less conspicuous, but it may
result in the recording of the strong high fre
quency peaks at such amplitudes that they will
not be properly reproduced.
Such peaks had
better not be recorded at full strength, because
the failure of the reproducing stylus to prop
erly follow the groove causes r-asping and chat
tering sounds and results in excessive record
wear.
'
One method of avoiding the recording of the
30 strongest passages at such levels as to cause ex
cessive groove curvature, while at the same time
maintaining a high general level, is to employ
an over-loading or saturating ampli?er which
cuts off the peaks of both high and low fre
quency signals. This, however, is not satisfac
tory for the reason that the limiting action of
the ampli?er Would act on many of the low fre
quency peaks, which do not need to be so lim
40
ited. In accordance with the aforesaid appli
cation, this difficulty is avoided by (l) segregat
ing the high and low frequency components, (2)
passing the high frequencies through an ampli
?er adjusted to saturate and cut off excessive
peaks, (3) passing the low frequencies through
45 an ampli?er which. does not cut off the peaks and
(4) utilizing the combined outputs of the two
ampli?ers to actuate the record cutter.
The present invention differs from that dis
closed by the aforesaid application in that the
curvature limiting effect is con?ned to the par
ticular waves Where the curvature would be ex
cessive. For example, if a sound wave consists
of components of several different frequencies,
there are points at which the curvature due to
.55
all the components add. If the curvature is re
duced only at such points, the unnecessary dis?
tortion resulting from uniform treatment of the
frequency group is avoided.
_
In carrying out the invention, I may employ
a wax cutter of the type at present in general
use for making phonograph recordings, namely
one in which the velocity of movement of the
cutting stylus is proportional to the instantaneous
value of the applied voltage, and I operate this '
cutter by means of an ampli?er which modi?es 19
the voltage fed to the cutter in such a way that
the rate of change of the voltage never exceeds
a certain predetermined value. When such a
cutter as I have described is used, the slope of
the groove, or the tangent of the angle which the 15
groove makes with the mean groove direction,
is proportional at a given linear record speed,
to the applied voltage, and the curvature of the
groove is proportional to the time rate of change
of this voltage. For the purpose of limiting the s
rate of change of the voltage supplied to the
cutter, the voltage e1, which would usually be
ampli?ed and applied to the record cutter is
?rst put through an ampli?er ‘stage which pro
25
duces a voltage 62 proportional to
d3,
dt
which is proportional to the ?nal curvature. The
voltage 62 is subjected to a modifying or lim
30
iting circuit. The resulting modi?ed voltage e’z
is then applied to another ampli?er stage which
integrates it with respect to time giving
35
The voltage 63 is then ampli?ed and applied to
the cutter. Voltage 63 is of the same wave shape
as voltage 61 except for the limits imposed on the
extreme rates of change as previously indicated. 40
The invention will be better understood from
the following description. when considered in
connection with the accompanying drawing, and
its scope will be pointed out in the appended
45
claims.
Referring to the drawing:
,
Fig. 1 illustrates the condition existing when
the groove curvature of a lateral cut record be
comes equal to that of the stylus. Although the
groove Was cut with a ?nite curvature, the stylus
tip must change its direction abruptly, or un
dergo in?nite acceleration as indicated by the
dotted line.
Fig. 2 illustrates the condition existing when
the record curvature of a lateral cut record ex
55
2
2,122,207
ceeds that of the stylus. Here it is quite impos~
sible for the stylus to follow the path of the
axis of the groove, and cutting away of the record
lowest frequency to be recorded. Under these
conditions, the voltage at the plate of the tube
will be proportional to the time rate of change
material occurs immediately.
Fig. 3 is a wiring diagram of a four stage am
of the voltage impressed on the input terminals
I3. At any given record velocity, the groove cur
pli?er wherein a reactor in the plate circuit of
the ?rst stage converts the input voltage e1 into
a voltage e2 which is proportional to
rig
10
d1‘
a limiting device in the plate circuit of the
second stage cuts off excessive peaks producing
a modi?ed voltage e’z, a condenser in the plate
15 circuit of the third stage integrates the voltage
e’z with respect to time, producing a voltage
vature is proportional to the rate of change of
the slope. The voltage at the plate of the ?rst
tube is proportional to the curvature of the groove
to be cut. The blocking condensers and grid
leaks shown in the various stages of the ampli 101
?er are assumed to have large enough capacities
and resistances to transfer the plate alternating
current voltages to the grids of the next stages
with negligible phase shift and without appre
ciable change in magnitude.
For limiting the peaks of the ampli?ed voltages
a limiting device is connected in the plate circuit
Of the tube l6. This limiting device includes a
transformer 20 through which potential is ap
and the fourth stage ampli?es the voltage es and
applies it to the record cutter.
Fig. 4 illustrates an alternative connection for
the plate circuit of the ?rst tube of the ampli?er
illustrated by Fig. 3, but performing a similar
di?erentiation of the voltage e1.
Fig. 5 is an explanatory diagram relating to
the operation of the current limiting device con
nected in the second stage plate circuit of the
ampli?er of Fig. 3.
30
Fig. 6 illustrates the stylus and groove rela
tion required to avoid improper action of the
stylus in the case of a hill and dale or vertical
cut record.
Fig. '7 is an explanatory diagram relating to
35 the operation of an ampli?er suitable for pro
ducing the relation indicated by Fig. 6, and
Fig. 8 illustrates how the second stage of the
ampli?er of Fig. 3 may be modi?ed to allow ad
justment of the record curvature as the distance
40 of the groove from the center of the record
changes.
Fig. 1 illustrates a sound record groove l6
which has a curvature substantially equal to that
of its cooperating stylus ll. Distortion of the
45 reproduced wave occurs with sharp groove cur
‘vatures even before the condition illustrated in
Fig. 1 is reached. When the curvature of groove
becomes equal to that of the needle, or stylus tip,
as shown in Fig. 1, there is established a limiting
50 condition beyond which the stylus can not follow
the groove and chattering and excessive record
wear are produced. This condition is illustrated
by Fig. 2 wherein the curvature of the groove l2
exceeds that of the stylus I l which fails to follow
55 the groove and damages the record. This con
dition is much more harmful than that which
would be produced by reducing the groove curva
ture sufliciently to permit the stylus to follow
the groove. An ampli?er adapted to produce this
60 result is illustrated by Fig. 3.
The ampli?er of Fig. 3 includes input terminals
I 3 to which an audio frequency voltage suitable
in wave form for operating a cutter of the type
previously mentioned is applied, and output ter
minals iii through which the modi?ed audio fre
quency voltages can be impressed on the operat
ing coil of the record cutter. Between terminals
l3 and M are interposed ampli?er stages l5, I6,
i‘! and i8. Connected in the plate circuit of the
70 stage it is a reactor iii of such value that at the
highest frequency of the sound spectrum to be
recorded, its rea-ctance will be substantially lower
than the plate resistance of the tube I5. The re
actor i? must also be so designed that its resist
ance is low compared with its reactance at the
plied to a full wave recti?er 2i of any suitable 20
type, and a bias potential source 22 which en
sures that no recti?cation takes place until the
voltage developed in either half of the secondary
of the transformer 28 exceeds the bias voltage.
Voltages higher than this cause a loading of the
plate of the tube it which prevents its swinging‘
much further. Otherwise expressed, the tube l6
loaded with the recti?er 2! has a letter S char
acteristic such as that illustrated in Fig. 5
wherein the characteristic is indicated at A, the
input wave at B and the output wave at C. A
break in the characteristic is illustrated at D
where the recti?er takes hold, and the resulting
?attening of the tops of the output wave is shown
in curve C. The fact that the recti?er tubes 2!
have a higher resistance for very small currents
than for higher currents, has the effect of round
ing off the shoulder D in the characteristic curve
A. The effect of the recti?er is to round off the
tops of the waves which have high peaks, but it 40
produces no distortion of waves whose peak volt
ages are less than the voltage of the biasing
source 22. This limiting device is adjusted so as
to operate only when the curvature of the result
ing groove would, without the limiter, be greater
than the predetermined allowable maximum.
Various modi?cations of the limiting device are
feasible. For example the tubes 25 might be re
placed by crystal or copper oxide recti?er units,
and the transformer 25! might be replaced by a
choke or resistance feed and the limiting device
operated through a blocking condenser. It would
also be possible to obtain the desired limiting
action by proper selection of the type of tube
to be used at it and operating it under suitable
conditions such as plate and. grid voltages, and
cathode temperature. ‘The arrangement shown
in Fig. 3, however, is simple in principle and
readily adjusted.
Having limited the voltage which is propor 60
tional to curvature. it is next necessary to apply
this voltage in such a way as to again obtain a
voltage suitable for operating the cutting device,
namely a voltage proportional to the slope of the
desired record groove. The conversion of voltage
proportional to curvatinie to one proportional to»
the slope is a step in the opposite direction from
that previously taken. One of the most satis
factory ways of accomplishing this is to load the
tube H’ of the next stage with a condenser 23 70
so large that its reactance is small compared
with the resistance of the plate circuit for all
frequencies to be recorded. The voltage across
this condenser is proportional to the time integral
of the voltage impressed on the grid of the tube, 75
3
2,122,207
or to the slope of the desired groove, and after
further ampli?cation may be applied to
ably designed cutter.
a suit
The action of the loading reactor I9 is such
as to cause an‘ accentuation of the high fre
circuit high as compared with the inductive re
actance of the coil, and by so designing any
intervening amplifying or other apparatus that
it introduces negligible distortion.
quency components in the same proportion that
to aiTect the current and to compensate for this
these contribute more to curvature than do low
frequency components having the same voltage
10
at the input end of the devicepbut ‘all com
ponents may contribute to produce maximum
curvature in the record groove and they also con
tribute in identical manner to the production of
maximum voltage at the limiting device. Were
the movement of the cutter stylus controlled by
inertia rather than mechanical resistance, the
by employing appropriate compensating circuits
between tube I8 and the cutter.
The advantages of the curvature limiting sys
tem herein described are not limited to a cutter
of the present mechanical resistance controlled
type, but may be realized in connection with an
inertia controlled cutter. Were it possible practi
cutter coil could be supplied with current propor
cally, to employ a cutter whose movements were
controlled by inertia only, throughout the entire 15
range of frequency to be recorded, the integrat
tional to the voltage applied to the grid of tube
IT. The limiting device could then operate to
limit the extreme acceleration to which the cutter
20 stylus is subjected. Since the cutters customarily
used at the present time have their movements
controlled by mechanical resistance rather than
ing operation performed by condenser 23 of Fig. 3
inertia reactance, this characteristic is taken
care of by loading the‘ third tube I’! with a
capacity 23. The reactance of this capacity is so
small in comparison with the plate resistance of
the tube that it does not appreciably influence
the magnitude or wave shape of the alternating
currents in the anode circuit, but these currents,
which are identical in wave form with the voltage
impressed on the grid of tube ll,‘ result in a volt
age across the terminal of the condenser 23, whose
waveform is the integral of that of the'current.
The action of the capacity accentuates the low
frequencies and exactly neutralizesthe effect of
the reactance l9 except insofar as the limiting
device may have operated.
_
On the other
hand, it is also permissible to permit coil reactance
'
Assuming for illustration that a 2000and a 4000
cycle wave, one volt each, are impressed at the
40 terminals l3, the 4000 cycle wave would produce
on the grid of the third tube ll, twice the volt
age produced by the 2000 cycle wave, If the 2000
cycle wave produces one volt at‘ the grid of the
tube H, the4000 cycle wave produces vtwo7volts
and the two waves together would produce three
volts if they happen to add in phase. ‘If the bias
device 2i is set for less than 3 volts the'limiter
would act on this combined peak. The con
denser 23 which has twice the impedance at 2000
would not be required.
With inertia control of
cutter movements, the acceleration of the stylus
will be proportional to the electromagnetic force 20
developed, and since stylus acceleration is pro
portional to groove curvature, the force for op
erating the cutter (which I am assuming to be
proportional to current) should be of the same
waveshape as the voltage applied to the grid of 25
tube IB. If, as would in general be the case, the
inertia control .of the cutter holds over only a
part of the required frequency range, compensa
tion as for example by a loading condenser as
shown in Fig. 3 would be needed, the compensa 30
tion being effective over that part of the fre
quency range in which the stylus movements are
controlled by mechanical resistance or factors
other than inertia.
If a cutter is employed having resistance con 35
trol through part of the frequency range and
inertia control through some of the higher fre
quency range, the correct relation for proper op
eration of the cutter is maintained by employing
a resistance 24 in series with a capacity 23. This
resistance should be of‘ such value that the
capacity reactance and the resistance become
equal at the same frequency that the mechanical
resistance of the cutter becomes equal to its
inertia reactance. Practically all cutters have 45
of necessity a certain amount of elastic sti?ness
in the mounting of the movable parts. There
will be a range of frequencies in the low fre
.It should be understood that stylus accelera
quency end of the sound spectrum, within which
this stiffness will predominate over the mechani
cal resistance. When cutter movement is con
trolled by elasticity of the armature and stylus
mounting (rather than by mechanical resistance
or by inertia) the amplitude (instead of the slope
or curvature) of the groove wave is proportional
to the current supplied. The relation between
tion is a measure of groove curvature. However,
amplitude and curvature corresponds to integrat
cycles that it has at 4.000 cycles functions to re
store the original ratio of voltages of the high
and low frequency components so that a wave
shape suitable for operating a standard cutter is
obtained.
1
since the cutter is designed so that the stylus
velocity (rather than acceleration) is propor
tional to current supplied, and velocity is the in
(50 tegral of acceleration, the correct relation is
maintained by impressing the voltage which is
proportional to acceleration on the grid of the
tube ll, the capacity load on the plate circuit of
this tube being utilized to provide an integration
and thereby produce a voltage proportional to
velocity, which is the integral of acceleration.
This voltage is impressed on the grid of tube [8
and a current of identical wave form sent
through the cutter coil. In practically all elec
tromagnetic systems the force developed is pro
portional to the current. Therefore, the current
through the actuating coil should be proportional
to and in phase with the voltage applied to the
grid of tube It, a condition which can in general
be met by making the resistance of the cutter
ing twice. In order therefore to drive a sti?ness
controlled cutter, an additional stage of correc
tion or integration of the same type employed
between tubes ll and i8 of Fig. 3 would be re
quired.
Since the elastic control however, pre
dominates over resistance through only a frac
tion of the frequency scale, in this extra stage
the loading capacity (corresponding in circuit
location to condenser 23) should have such a
value that its reactance becomes equal to the
resistance in series with it (corresponding to re
sistance 24) at the same frequency that the
elastic reactance in the cutter becomes equal to 70
its mechanical resistance. Since .the extra in
tegration stage would have the e?ect of raising
the voltage of the low frequency components as
compared with those of higher frequency, it may
be desirable to offset this e?ect by reducing the
2,122,207
relative amount of low frequency voltage applied
to the input terminals I3. Such relative reduc
tion of low frequency components is at present
obtained by allowing cutter elastic reactance to
predominate over mechanical resistance in the
low-frequency range, and is useful in preventing
excessive amplitudes of cut which might other
through condenser 25 and resistance 26 is equal
to the voltage at the plate of tube I5 divided by
the capacity reactance. The drop across the re
sistance which is proportional to this condenser
charging current, which is proportional to the
rate of change of the impressed voltage.
This
resistance drop may be impressed on the grid of
wise cause cutting over between adjacent grooves, the following tube I6.
since the low frequency components while con
The ampli?er tubes I5, I6, I‘! and I8are not
10 tributing little to groove curvature, contribute
strictly essential to carrying out the differentia 10
very largely to amplitude. If the cutter elastic tion, limiting and integration functions of the
reactance exceeds the mechanical resistance only circuits of Figs. 3 and 4, but serve in a valuable
at the very lowest frequenci.es,-the compensation way to isolate the several special circuits, so they
or extra integration stage mentioned above may will not react on each other, and also to make up
15 prove unnecessary.
for the losses of voltage which would otherwise 15
It will be evident from the foregoing discussion occur.
that the application of my invention does not
In the case of hill and dale records, there are
require that any particular design of cutter be also limits to the curvatures which the reproduc
employed, but a cutter of given characteristics ing stylus can follow, but here the problem as
20 having been chosen, electrical compensating cir
sumes somewhat different aspects. Fig. 6 shows 20
cuits can be designed and applied between the the shape that would have to be given the groove
tube I8 and the cutter, to give the desired over-‘ bottom in order to cause the center of the stylus
all characteristic. The desired over-all char
tip to follow a sinusoidal path, indicated by the
acteristic, for the purpose of invention, is such dotted line. As will be seen from Fig. 6, it is de
25 that the curvatures in the groove as cut will be
sirable to cut the groove of a hill and dale type
proportional to the limited or modi?ed voltage of record with sharp hills and long Valleys to
6'2. Methods of compensating to obtain desired facilitate tracking of the stylus. In order to limit
over-all characteristics are well known in the the curvature only in one direction or in valleys
sound recording art, and examples have already of the record, the ampli?er should have a char
30 been described herein, covering the cases which
acteristic similar to that illustrated in Fig. '7 30
are most likely to arise. It is not even necessary wherein E represents the tube characteristic, F
that the record be of the present almost univer
the input voltage wave, and G the output voltage
sally used type in which the slope of the groove wave. Such a characteristic may be obtained
is approximately proportional to the instan
with the ampli?er of Fig. 3 by omitting the limit~
35 taneous pressures in the sound at the micro
ing device and biasing the grid of tube I‘! so that phone. Were the reproducing devices to be em
it operates on a strongly curved characteristic.
ployed of a different type, responding for example An alternative arrangement for producing the
to de?ection rather than velocity of the needle, a same result is to employ a single anode recti?er
different form of record groove would be called with suitable bias potential in place of the double
for, but it would be desirable to limit extreme acting recti?er of Fig. 3. Such a recti?er may for
40
curvatures in exactly the same manner. The
example be utilized to impose a heavy load on
application of a curvature limiting device is how
the positive swings and a smaller load for the
ever appropriate only in View of the ?nite mass
of the reproducing stylus and the ?nite curvature
45 of the stylus tip, which is an unavoidable feature
in all mechanical reproduction.
A cutter of the design at present in wide use,
in which several compliances and masses inter
vene between the armature and stylus constitutes
50 a mechanical low pass ?lter. Such a cutter pro
duces large phase shifts near the upper end of the
frequency range and these phase shifts are very
dif?cult to compensate. In order to avoid such
dii?culties, it is desirable to limit the maximum
frequency supplied to the input terminals I 3 to a
value well below that at which the mechanical
?lter properties of the cutter take effect. This
can be accomplished by suitable ?lters interposed
between the sound pick-up device and input ter
60
minals I3.
'
Fig. 4 shows a type of circuit which may be
employed in place of the reactor IS between the
?rst two stages of the ampli?er of Fig. 3. In this
circuit use is made or" the fact that the current
65 through a condenser is proportional to the rate
of change of the voltage impressed across the
condenser.
A condenser 25 is employed, having
such small capacity that at no time does it, nor
the resistance it, constitute an appreciable load
70 on the plate of the tube I5. The voltage at the
plate of tube i5 is then equal to a constant times
the voltage impressed on the grid of tube I 5.
The resistance 26 is also low in comparison with
reactance of condenser 25, so that throughout
the essential frequency range the current ?owing
negative swings.
Since the linear speed of the record becomes
less as the center is approached, the recorded 45
waves are shorter and consequently the curva
tures are increased. It is therefore desirable to
change the curvature controlling or limiting
characteristic as the record progresses. This can
be readily accomplished in the case of the limit
ing device of Fig. 3 by continuously decreasing
the Voltage of the biasing device 22, but I prefer
toaccomplish the same result by modifying the
50
connections of stages I6 and IT as indicated by
Fig. 8 which shows two gain controls 2'! and 28, 55
one preceding and the other following the tube
I6 and both operated by single control member
3|, so that there is a ?xed relation between the
positions of the two. As the center of the record
is approached, the ?rst control is turned up and 60
the second control turned down to exactly equal
ize the over-all gain, but to increase the voltage
applied to the limiter or curvature controlling
device, thereby causing it to operate at continu
ously lower cutting tool amplitudes. The type of
apparatus illustrated in Fig. 8 can'be applied
to the curvature controlling system for either
lateral or hill and dale records.
Having thus described my invention, I claim:
1. A sound recorder including a multi-stage
ampli?er, means connected in the plate circuit
of a leading stage of said ampli?er for converting
acoustically modulated voltage to a voltage pro
portional to the rate of change of said acoustical
ly modulated voltage, and means connected in a 75
5
2,122,207
following stage of said ampli?er for suppressing
excessive peaks in said converted voltage.
2..In combination with a sound recorder, a
multi-stage ampli?er, means connected in the
plate circuit of a leading stage of said ampli?er
for converting acoustically modulated voltage to
a voltage proportional to the record groove cur
vature, and a biased recti?er connected in the
plate circuit of a following stage for suppressing
excessive peaks of said converted voltage.
, 3. A sound recording system including a multi
stage ampli?er, means connected in the plate
circuit of a leading stage of said ampli?er for
converting acoustically modulated voltage to a
voltage substantially proportional to the record
15
groove curvature, means connected in an inter
mediate stage of said ampli?er for suppressing
excessive peaks of said converted voltage, and
means connected in a following stage of said am
20
pli?er for integrating said peak-suppressed volt
age to a wave form similar to that of said acousti
cally modulated voltage except for the suppres
sion of said peaks.
4. A sound recording system including a se
25 quence of electrical circuits, means connected in
a leading stage or" said system for converting
acoustically modulated voltage to a voltage pro
portional to the rate of change of said acoustical
ly modulated voltage, means connected in an in
30 termediate stage of said system for modifying
peaks of said converted voltage, and means con—
nected in a following stage of said system for
integrating said modi?ed voltage to a wave form
similar to that of said acoustically modulated
35 voltage except for the modi?cation of said peaks.
5. A sound recording system including a multi
stage ampli?er, means connected in the plate cir
cuit of a leading stage of said ampli?er for con
verting acoustically modulated voltage to a volt
age proportional to the rate of change of said
acoustically modulated voltage, means connected
in an intermediate stage of said ampli?er for
asymmetrically modifying said converted volt
age, and means connected in a following stage of
.45 said ampli?er for integrating said modi?ed volt
age to a wave form similar to that of said acousti
cally modulated voltage except for the action of
the said modifying means.
6. A sound recording system including a multi~
.stage
ampli?er, means connected in the plate cir
50
cuit of a leading stage of said ampli?er for
converting acoustically modulated voltage to a
voltage proportional to the record groove curva
ture, means for suppressing peaks in said con
.55 verted voltage, and means operable to vary the
effect of said peak suppressing means without
changing the gain of said ampli?er.
'l. A sound recording system including a multi
stage ampli?er, means connected in the plate
circuit of a leading stage of said ampli?er for
converting acoustically modulated voltage to a
voltage proportional to the rate of change of
said acoustically modulated voltage, means for
modifying the wave form of said converted volt
65 age, and means operable to vary the effect of said
wave form modifying means: without changing
the gain of said ampli?er.
8. The method of recording an acoustic-ally
modulated voltage which includes converting said
70 voltage to a voltage proportional to the curvature
of the record groove, modifying excessive peaks
of said converted voltage, integrating said peak
modi?ed voltage whereby a voltage is obtained
similar to that of said acoustically modulated
75 voltage except for the modi?cation of said peaks,
and varying the degree of modi?cation, of said
peaks.
9. The method of recording an acoustically
modulated voltage by means of an electrically
actuated record cutter, which includes convert
ing said voltage to a voltage substantially pro
portional to the curvature of the desired record
groove, asymmetrically modifying peaks of said
converted voltage, integrating said modi?ed volt
age whereby a voltage is obtained suitable for 10
operating said record cutter, and varying the‘ de
gree of asymmetrical modi?cation of said peaks.
10. The method of recording an acoustically
modulated voltage by means of an electrically
actuated record cutter, which includes convert 15
ing said voltage to a voltage substantially pro
portional to the curvature of the desired record
groove, suppressing excessive peaks of said con
verted voltage, integrating said peak suppressed
voltage whereby a voltage is obtained suitable for
operating said record cutter, and varying the sup
pression of said peaks.
11. A sound recording system including means
for converting acoustically modulated voltage to
a voltage proportional to the rate of change of 25
said acoustically modulated voltage, and means
having non-linear characteristics for modifying
said converted voltage.
12. A sound recorder including means for con
verting acoustically modulated voltage to a volt 30
age proportional to the record groove curvature,
means for modifying the peaks of said converted
voltage, and means for integrating said modi?ed
voltage to a wave form similar to that of said
acoustically modulated voltage except for the 35
modi?cation of said peaks.
13. A sound recorder including means for con-
verting acoustically modulated voltage to a volt
age proportional to the record groove curvature,
means for suppressing the peaks of said converted 40
voltage, and means for integrating said peak sup
pressed voltage to a wave form similar to that
of said acoustically modulated voltage except for
the suppression of said peaks.
14. The method of amplifying an alternating
voltage to be recorded which includes converting
said voltage to a voltage proportional to the rec
0rd groove curvature, suppressing excessive peaks
of said converted voltage, and integrating said ‘
peak suppressed voltage to a wave shape which 50
is similar to that of said alternating current volt
age except for the suppression of said peaks.
15. The method of recording acoustically
modulated voltage which includes converting said
voltage to» a voltage proportional to the record 55
groove curvature, suppressing excessive peaks of
said converted voltage, integrating said peak sup
pressed voltage to a wave form which is similar
to that of said acoustically modulated voltage ex
cept. for the suppression of said peaks.
60
16. In an impulse recorder, a multi-stage am
pli?er, reactance means connected with a lead
ing stage of said ampli?er for converting the
impulses to be recorded to impulses substantially 65
proportional to the record curvature, and a non
linear circuit connected with an intermediate
stage of said ampli?er for modifying the wave
shape of said converted impulses.
17. In an impulse recorder, a multi-stage am
pli?er, reactance means connected with a leading
stage of said ampli?er for converting the im
pulses to be recorded to impulses substantially
proportional to the record curvature, and a biased
recti?er connected with an intermediate stage of 75
6
2,122,207
said ampli?er for suppressing excessive peaks of
said converted impulses.
18. An impulse recorder including a multi
stage ampli?er and a record cutting device, a
reactance connected with a leading stage of said
ampli?er for converting the impulses to be re
corded to impulses substantially proportional to
the record groove curvature, a. biased recti?er
connected with an intermediate stage of said’am
pli?er for suppressing peaks of said converted
impulses, and reactance means connected with
.a following stage of said ampli?er for integrating
said peak suppressed impulses to a wave form
suitable for operating said record cutting device.
19. An impulse recorder including a multi-stage
ampli?er, and a record cutting device, reactance
means connected with a leading stage of said am
pli?er for converting the impulses to be recorded
to impulses substantially proportional to the rec
ord groove curvature, a biased recti?er connected
with an intermediate stage of said ampli?er for
suppressing peaks of said converted impulses, and
means operable independently of the gain of said
ampli?er for adjusting the effect of said recti?er
on said peaks.
20. In a sound recording system means for pro
ducing a voltage proportional to the curvature
of the desired record groove, means for modifying
the wave form of said voltage, and means includ
ing an electrical compensating circuit for caus
ing a recording stylus to undergo acceleration
proportional to said modi?ed voltage.
21. In a sound recording system means for pro
ducing a voltage proportional to the curvature of
r the desired record groove, means for modifying
the wave form of said voltage, means including
an electrical compensating circuit for causing a
recording stylus to undergo acceleration propor
tional to said modi?ed voltage, and means related
40 to the position of the cutting device relative to the
center of the record, for altering the degree of
action of said Wave form modifying means.
22. A sound recording system including means
for converting acoustically modulated voltage to
45 a voltage substantially proportional to the record
groove curvature, means having non-linear char
acteristics for suppressing peaks of said converted
voltage, and means responsive to said peak
suppressed voltage for cutting a record groove
50 whose slope is proportional to the integral of said
peak suppressed voltage.
23. A sound recording system including means
for converting acoustically modulated voltage to
a voltage substantially proportional to the record
groove ‘curvature, means having non-linear char
acteristics for modifying said converted voltage,
and means responsive to said modi?ed voltage for
cutting a record groove whose slope is propor
tional to the integral of said modi?ed voltage.
24. In a sound recording system for hill and
dale records, means for producing a voltage sub
stantially proportional to the curvature of the
desired record groove, means including an elec
trical circuit having non-linear characteristics
for modifying said voltage whereby the peaks of
one polarity are increased relative to those of
the opposite polarity, and groove cutting means
responsive to said modi?ed voltage having such
characteristics that the vibratory velocity of the
cutting stylus is proportional to the time inte
gral of said modi?ed voltage.
25. In a sound recording system for hill and
dale records, means for producing a voltage sub
stantially proportional to the curvature of the
desired record groove, means including an elec
trical circuit having non-linear characteristics
for modifying said voltage whereby the peaks of 10
one polarity are reduced relative to those of the
opposite polarity, and groove cutting means re~
sponsive to said modi?ed voltage having such
characteristics that the vibratory velocity of the
cutting stylus is proportional to the time integral
of said modi?ed voltage, and means for changing
the effect of said modifying circuit whereby it
produces greater wave shape alterations when
the cutting device is operating near the center of
the record.
26. In a sound recording system for hill and
dale records, means for producing a voltage sub
stantially proportional to the curvature of the
desired record groove, means including an elec
trical circuit having non-linear characteristics
for modifying said voltage whereby the peaks of
one polarity are reduced relative to those of the
opposite polarity, groove cutting means respon
sive to said modi?ed voltage having such char
acteristics that the vibratory velocity of the cut 30
ting stylus is proportional to the time integral
of said modi?ed voltage, and means for changing
the effect of said modifying circuit whereby the
smaller the radius of the groove being cut the ,
greater is the effect of said non-linear circuit in
modifying the wave shape.
27. The method of modifying an alternating
voltage to be recorded which includes production
of a second voltage proportional to the rate of
change of said original voltage and suppressing 40
in said second voltage peaks of one polarity rela
tive to the peaks of the opposite polarity.
28. A vertically out sound record in which the
curvature at the bottoms of the valleys have
been decreased independently of the record mate 45
rial resistance and relative to the curvatures at
the tops of the hills.
29. The method of recording sound which
comprises producing a voltage substantially pro
portional to the rate of change of pressure in the 50
sound waves to be recorded, causing a non-linear
distortion of said voltage, and cutting a record
groove having a slope proportional to the instan
taneous value of the time integral of said dis
torted voltage.
,
U! in
30. The method of cutting a sound record
groove which comprises the production of a volt
age substantially proportional to the rate of
change of pressure in the sound to be recorded,
causing a non-linear distortion of said voltage
wave, causing the degree of said distortion to vary
in accordance with the radius of the groove being
cut, and causing the cutting stylus to undergo
accelerations proportional to the instantaneous__
values of said distorted ‘voltage.
EDWARD W. KELLOGG.
65
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