US2324781A - Arrangement for the reproduction of sound - Google Patents

Arrangement for the reproduction of sound Download PDF

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US2324781A
US2324781A US435332A US43533242A US2324781A US 2324781 A US2324781 A US 2324781A US 435332 A US435332 A US 435332A US 43533242 A US43533242 A US 43533242A US 2324781 A US2324781 A US 2324781A
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valve
control
sound
output
applying
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US435332A
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Kolb Otto Kurt
Boston David Whitehead
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BRITISH ACOUSTIC FILMS Ltd
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BRITISH ACOUSTIC FILMS Ltd
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    • GPHYSICS
    • G11INFORMATION STORAGE
    • G11BINFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor

Description

July 20, 1943. Q K, KOLB ET AL 2,324,781
ARRANGEMENT FOR THE REPRODUCTION OF SOUND Filed March 19, 1942.
Patented July 20, 1943 i d ARRANGEMENT FOR THE REPRODUCTION O'F SOUND vOtto Kurt Kolb and David Whitehead Boston, f London, England, assignors to British Acoustic Films Limited, London, England, a British company Application March 19, 1942, Serial No. 435,332 In Great Britain April 4, 1941 7 claims. (o1. 17e-100.3)
fThis invention relatesto the recording and reproduction of sound with thefuse of sound film records. Picture iilms have been provided with one or more sound tracks and witha control track adapted to control amplilication duringl reproduction,` the control `track being arranged `within or substantially within the strip of the film occupied by the sprocket perforation holes "at one edge of the iilm. Each of the two perforation strips of the lm may be provided with such a. control track.
According to the specification of British Patent No. 473,256, foriexample, the sound is recorded on the sound track under volume "compression, and the amount of compression is registered vby the amplification of the .reproducing amplifier.
Bythis arrangement an expansion of the volume of thefrecorded sound iseliected the reproductiontaking place L through on amplifier channel;
n 4Such an arrangement suffers from'one draw.-
` lback inasmuch as the maximum volume of undlstortedsound reproducible is limited `by` the output capacity of the amplifier; This does not matter for dialogue and quiet musical pieces which make up the greater part of a soundl accompaniment to a lm, but it does place a limitation on the artistic interpretation of `fully o`r chestrated musical passages and on special ef- `fects such as gunfire, running engines and the like. The principal object of the presentinvention is to overcome this drawback by making use of a control current derived from a track or tracks in the sprocket hole line of the film to expand the volume range of the recorded sound in an" improved manner by the use of one or more `additional amplifierr channels and so to ,in-
crease the maximum -volume of sound repro!- diicible and td'enhance the realism ofthe reproduced sounds. l
" A further object is to enable a control current to be'derived from a control track-or tracks located within the sprocket hole strip of iilmv and to apply this control current tocontrol a further reproducing amplier `or ampliiiers ad'- dltional to the main reproducing ampliiier.
when one additional ampliner is provided, the output from this additional amplifier may be fed to the same loudspeaker or` loudspeakers as those to which the outputfrom the mein ampliiier is fed, or, it may be fed to additional loudspeakers. vThe arrangement may also be such that the low frequency sound currents from the main and additional amplifiers are all feti to the same low frequency loudspeaker Whilst the high frequency currents are fed to separate loudspeakers.
The additional amplifier need not have the same frequency characteristics as the main `amplifier, for example, it can be designed to deal with onlya `small range of frequencies. so that it may be of simple design and inexpensive 9.0111: struction. .Moreoverl the additional amplifie! will preferably have a much greater power out.- put than the main amplier. I
One feature of the invention resides 1n the provision of a control unit which is fed 'with current derived from the sound track Proper .011 the film and also with current derived from the control track or tacks, and is so arranged as either to control all the amplifiers, including the main amplifier, or only to bring in one or more additional amplifiers as and when required` The invention will now be described, by'way of example, with reference to the accompanying drawing, wherein-- J i Figure 1 shows a diagramof one embodiment according to the invention wherein current from the sprocket hole control track controls both the main amplifier and an additional ampliiier.V
Figure 2 shows a diagram of a modification of the embodiment according to Figure 1 wherein only the additional Vampliiier is so contro11ed.`
Figure 3 illustrates an embodiment of the cir:` cuit arrangement of the control unt'shown m Figure l, and l n n Figure 4 illustrates an embodiment ,of the cir,- cuit arrangement of the control unit shownin Figure 2. i i A n Figure 5 shows a small portion of a film with the sound and .control tracks thereon. l f i Referring to Figures ,il and j2, C represents the conventional light-sensitive cell and` optical syse' tem and `HA representsv the normal head ame p'lifier such as is fitted to 'present day sound lm projectors. :This amplier is used to amplify photo-electrically produced sound l currents obthe sound track 3 adjacent the sprocket holes at the same side of the film. CI represents a light sensitive device, such as a photo-electric or selenium cell, which, together with its optical system, is used to produce a control current from the control track in the line of the sprocket holes on the film.
A further cell and optical system, C2, is also shown in dotted lines; this cell can be used to produce a control current from a second control track, if one is provided vin the line of the second set of sprocket holes 2 on the film.
The outputs from the devices HA and CI are fed to a collecting unit or fader F. Such a fader is provided for the manual adjustment of the sound film projector and also for facilitating changing over from one projector to another as is necessary at the end of each lm reel.
In Figure 1, both the currents fed to the fader F are passed on to a control unit CU which controls both the main amplifier MA and an additional amplifier AA which in turn supply current to the loud speakers LS.
In Figure 2, it Will be seen that the control current fed to the fader F is passed on to the control unit CU, as in Figure 1, whilst the sound track current is passed straight on to the main amplifier MA. A portion of this current from the head amplifier HA is, however, branched off from the connection between the fader and the main amplifier and fed to the control unit which thus only controlsrthe additional amplifier AA.
' In the arrangements shown in Figures l and 2 of the drawingv the control unit CU brings in the additional amplier AA at a certain amplitude ofthe control track and controls its amplification over a predetermined amplitude range. The outputs from the amplifiers MA and AA can be fed to the same or parallel loudspeakers LS; in fact, any Ydesired arrangement of speakers can be employed. Figure 3 illustrates an embodiment of the circuit arrangement of the control unit CU shown in Figure 1. A `light beam modulated by the sound track 3 of Figure 5 is focussed :on the light sensitive cell C, which may be ayphoto-electric cellor-selenium cell, and the output of the cell C is fed. to the head amplifier HA, the output from which is fed to the fader F. A light beam modulated by the control track I of Figure 5 is focussed on the light sensitive cell CI and the output from this cell, after amplification if de-. sired, is also fed to the fader F. From the fader it is passed. on. to the first valve Vi of the control unit.l
It will be appreciated that the light beam focussed on the cell CI consists of a modulated beam having a carrier frequency of 96 cycles per second, since at normal film feeding speed, 24 picture frames and therefore 96 sprocket holes will pass through the light beamevery second. Thetransformer TRI, fed with the output of the valve VI, is therefore tuned to this frequency. The output from the transformer TRI is rectified by a rectifier RI, smoothed by a filter circuit FCI and fed through the secondary of a transformer TR2 to bias the contro-l grid of a Variable mu valve V2. The transformer TR2 is also connected to the fader F and fed with the output from the head amplifier HA. The output from the Valve V2 is fed via a transformer TRS tothe main amplier MA, of usual design, the output of which is thus controlled in dependence upon the output of the said Valve.
The control grid of the valve V2 is biassed, as
for example by the battery BI, via a rectifier R2, the arrangement being such as to limit the maximum amplification gain of the valve. As a result, overloading of the valve with consequent distortion can be avoided and the valve can be made to handle currents only up to a desired maximum.
A portion of the control current is also fed via the rectifier RI, a second filter circuit FC2 and a further transformer TRII to the control grid of a further valve V3, which is also of the variable mu type.
The variable mu valve V3 is also fed with a portion of the signal current from the head amplifier via the fader and the transformer 'I'R4 and it is also biassed by the rectifier R3 and battery B2 in a similar manner to the valve V2 but to a different point on its working characteristic so that it only begins to function, for example, after the valve V2 has become loaded to its predetermined maximum. The output from the valve V3 is fed to` a transformer TR5 and from there it is passed on to the additional amplifier AA, the output of which is thus controlled in dependence upon the output of the valve V3. The lines designated IIT+ and HT- at their right hand ends represent the leads of the unit connected to the plus and minus terminals of a service of high tension electric current (not shown) as is usual in amplifier units.
Reference has already been made to the feature that the additional amplifier may be of simpler and less expensive construction than the main amplifier. In such a case it may occur that it gives rise to noticeable background noise during those periods when it is not reproducing sound passages, for example, when the main amplifier is reproducing only pianissimo passages. The valve V3 controlling the additional amplifier may therefore be provided with a switch or electrical relay, operated by hand or otherwise, to bring it into use only during those periods when itisunder the control of the control track. For example, an automatically operating electrical relay is indicated by the reference RL in Figure 3. This relay has a coil in series with the anode of valve V3, and is arranged to close its contact as soon as the valve V3 begins to operate but to open when the valve is not operating. As shown by way of example and in dotted lines, the relay RL may be used to open and close the output circuit of the additional amplifier AA, leading to a loudspeaker LS.
Figure 4 illustrates an embodiment'of the circuit arrangement of the control unit' CU shown in Figure 2. The arrangement so far as the head amplifierHA, control cell CI land fader F are concerned is the same as in Figure 3. However, in this embodiment, the signal currents frornthe head'amplifier HA are fed straight on to the main amplifier MA via the fader F and, consequently, the main amplifier does not come under'the control of the control unit. A part of the signal current from the head amplifier is branched off from the connection between the fader and the main amplifier and fed'to the control unit, that isgjto say, the transformer TR2. l The control current is obtained as above4 means of the valve VI, tuned transformer 'IRI, rectifier RI, iilter circuit FCI and transformer TR2 and applied to the control grid of the variable mu valve V2. This valve is also biassed by battery Bl Via aI rectifier R2 so as to limit the maximum amplification gain. The output fro-m the valve V2 is fed to the transformer TR3 and from there is passed on toy the additional amplier AA instead of to the main amplifier as in Figure 3; The circuit of valveVz may also be provided with a switching relay RL if desired, as in Figure 3. i
By the arrangement according to Figure 4, only the additional amplifier is controlled by the lcontrol track, and since this additional amplifier may have a maximum output several times that of the main amplifier, it will be appreciated that it is possible to employ it fo-r the reproduction of special effects, fully orchestrated musical pieces and the like, with great advantage.
Whilst in the foregoing specific embodiments of the invention the control of the amplifiers depends upon the amplitude of the control track I, it Will be understood that the control :can be effected by means of different frequencies carried by the control track.
We claim:
1. Apparatus for reproducing sound from film records such as are provided with at least one control track in line with the sprocket holes of the film in addition to the sound record track thereon, said apparatus comprising means for deriving aY sound current from said sound record track, means for deriving a control current from said control track, a main amplifier and an additional amplifier, a control unit including a first amplifying valve, means for applying said con-l trol current to the grid of said valve, a transformer tuned to a frequency corresponding to the rate at which ,the sprocket holes in the film which are in line with the control track pass through the apparatus means for applying the f output of said valve'to saidtransformer, a rectifier connected to the output of said transformer, `a second valve of a type adapted for variably controlled amplification, means for applying the output of said rectifier as a grid bias control to a grid circuit of said second valve, means for applying sound current to the input of said second valve, and means for applying the output of said second valve to the input of said additional amplifler.
2. Apparatus for reproducing sound from nlm records such as are provided with at least one control track in addition to the sound record track thereon, said apparatus comprising means for deriving a sound current from said sound record track,.means for deriving a control current from said control track, a main amplifier and an additional amplifier, a control unit including a first amplifying valve, means for applying said control current to the grid of said valve, a transformer and means for applying the output of said valve to said transformer, a rectifier connected to the output of said transformer, a second valve of a type adapted for variably controlled amplification, means for applying the output of said rectifier as a grid bias control to a grid circuit of said second valve, a constant vo-ltage source and means including a rectifier for applying a constant voltage therefrom to said grid circuit whereby the gain of said second valve may be limited, means for applying sound current to the input of said second valve, and means for applying the output of said second valve to the input of said additional amplifier.
3. Apparatus for reproducing sound from film records such as are provided with at least one control track in addition to the sound record track thereon, said apparatus comprising means for deriving a sound current from said record track, means for deriving a control current from said control track, a main amplifier and an additional amplifier, a control unit including a first amplifying valve, means for applying said control current to the grid of said valve, a transformer and means for applying the outputof said valve to said transformer, a rectifier connected to the output of said transformer, a second valveof a type adapted for variably controlled amplification, means for applying the output of said rectifier as a grid bias control to a grid circuit of said second valve, meansl for applying sound current to the input of said second valve, means for applying the output of said second valve to the input of said main amplifier, a third valve also of a type adapted for variably controlled amplification, means for applying grid bias control from` the output of said first valve to a grid circuit of said third valve, means for applying sound current to the inputof said third valve, and connections for applying current from `the output of said third valve to the input of said additional amplifier. l
4. Apparatus for reproducing sound from film records such as are provided with at least one control track in addition to the sound record track thereon, said apparatus means for deriving a sound current from. sai record trackfrneans for deriving a control current from lsaid control track, a main amplifier 'and an additional amplifier', a control including a first amplifying valve, means for applying said contro-l current to the grid of vaive, a transformer and means for applying the output of said valve to saidtransformer, a rectifier `connected to the output of said transformer, a second valve of a type adapted for variahly controlled amplification, means for applying the output of said rectifier as a grid bias control to a grid circuit of said second valve, inea-iis for applying sound current to the input of said second valve, means for applying the output of said second valve to the input of said main amplifier, a third valve also of a type adapted for variably controlled amplification, means for applying grid bias control from the output of said first valve to a grid circuit of said third valve, means for applying sound current to the input of said third valve, and connections for applying current from the output of said third valve to the input Vof said additional amplifier, a constant voltage source and means including a rectifier for applying a constant voltage therefrom to the grid circuit of said second valve whereby the gain of said valve may be limited, and means for applying a grid bias from such a constant voltage so-urce also to the grid circuit of said third valve.
5. Apparatus for reproducing sound from film records such. as are provided With at least one control track in addition to the sound record track thereon, said apparatus comprising means for deriving a sound current from said record track, means for deriving a control current from said control track, a main amplifier and an additional amplifier, a control unit including a first amplifying valve, means for applying said control current to the grid of said valve, a transformer and means for applying the output of said valve to said transformer, a rectier con nected to the output of said transformer, a second valve of a type adapted for variably controlled amplification, means for applying the output of said rectifier as a grid bias control to a grid circuit of said second valve, means for applying sound current to the input of said second valve, means for applying the output of said second valve to the input of said main amplier, a third valve also of a type adapted for variably controlled ampliiication, means for applying grid bias control from the output of said first valve to a grid circuit of said third valve, means for applying sound current to the input of said third valve, and connections for applying current from the output of said third Valve to theiinput of said additional amplifier, a constant voltage source and means including a rectifier for applying a constant voltage therefrom to the grid circuit of said second valve whereby the gain of said valve may be limited, and means for applying a grid bias from such a constant voltage source also to the grid circuit of said third valve, the value of the bias applied to the grid of said third valve being such that its coming into operation is delayed until after the second valve has been loaded to a substantial extent.
6. Apparatus for reproducing sound from film records such as are provided with at least one control track in addition to the sound record track thereon, said apparatus comprising means for deriving a sound current from said sound record track, means for deriving a control current from said control track, a main amplier and an additional amplier, a control unit including a first amplifying valve, means for applying said control current to the grid of said valve, a transformer and means for applying the output of said valve to said transformer, a rectier connected to the output of said transformer, a second valve of a type adapted for variably controlled amplification, means for applying the output of said rectifier as a grid bias control to a grid circuit of said second valve, means for applying sound current to the input of said second valve, means for applying the output of said second valve to the input of said additional amplier, and an electrical relay in the output circuit of said second valve adapted to bring said additional amplifier into operation only When current is flowing in the output circuit of said second valve.
7. Apparatus for reproducing sound from film records such as are provided with at least one control track in addition to the sound record track thereon, said apparatus comprising means for deriving a sound current from said record track, means for deriving a control current from said control track, a main amplier and an additional amplier, a control unit including a iirst amplifying valve, means for applying said control current to the grid of said valve, a transformer and means for applying the output of said valve to said transformer, a rectiiier connected to the output of said transformer, a second valve of a type adapted for variably controlled amplification, means for applying the output of said rectier as a grid bias control to a grid circuit of said second valve, means for applying sound current to the input of said second valve, means for applying the output of said second valve to the input of said main amplifier, a third valve also of a type adapted for variably controlled amplification, means for applying grid bias control from the output of said first valve to a grid circuit of said third valve, means for applying sound current to the input of said third valve, and connections for applying current from the output of said third valve to the input of said additional amplier, said connections including an electrical relay adapted to bring said additional amplifier into operation only when current is flowing in the output circuit of said third valve.
OTTO KURT KOLB. DAVID WHITEHEAD BOSTON.
US435332A 1941-04-04 1942-03-19 Arrangement for the reproduction of sound Expired - Lifetime US2324781A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2499587A (en) * 1947-02-14 1950-03-07 Rca Corp Control track sound distribution system and record therefor
US2557636A (en) * 1946-06-12 1951-06-19 Texas Co Amplifying and pulse selecting circuit for radiation detectors

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2557636A (en) * 1946-06-12 1951-06-19 Texas Co Amplifying and pulse selecting circuit for radiation detectors
US2499587A (en) * 1947-02-14 1950-03-07 Rca Corp Control track sound distribution system and record therefor

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