The Cine Technician (1935-1937)

120 The Journal of the Association of Cine-Technicians Dec, iq36-Jan., 1037 Sound Recording News from Western Electric The new type "OB" Portable Sound Film Recording System will be used at many of the new studios, including Denham, Pinewood and Amalgamated. Embodying numerous features of its predecessors, the type "F" and "FB" systems, the "QB" system represents the latest trend in film recording apparatus. The entire amplifier system has been re-designed electrically, the units modernised and many new features added to facilitate operation and maintenance. Refinements previously available only in studio operation are also incorporated. The mixer operator is given the choice of direct or photo-electric monitoring using a high quality moving coil headset, and provision is also made for an extension headset to the boom man to assist him in locating the . correct microphone position during takes. A novel order wire feature is also included in that the mixer operator, through his subset, may speak to the boom-man on the extension headphones by pressing the appropriate key on the mixer panel. Similarly, the mixer operator and recordist may converse with each other whilst wearing the monitoring headsets, thus obviating the necessity of removing the headsets to operate the order wire telephone. A reduction in the number of units employed is obtained by incorporating in the mixer unit three single stage preamplifiers rendering unnecessary the use of external microphone amplifiers. Provision is made, however, for the use of one external amplifer when desirable on long distance operation. Either the Western Electric 618-A Microphone or a new type non-directional 630-A Microphone may be used. Both are high quality moving coil microphones, the latter providing great freedom of movement on the part of actors relative to microphone position without affecting sound quality. Variable dialogue equalisation, high pass filter for elimination of set resonance effects, and low pass filter to offset light valve resonance are included. Ample facilities are available for checking light valve operation, which include a multifrequency oscillator with a fixed 1000 cycle output for making overload tests and setting noise reduction, and a variable frequency output for checking light valve tuning. An overload bridge, which may be inserted in the photoelectric monitoring circuit, provides a more sure determination of the clash or overload point by making quite audible the harmonics generated by the light valve when overloaded. The comparator feature has, however, been retained in the photo-electric unit, providing a second means of performing the foregoing tests, and a further stage of push-pull amplification additional to the one in the unit permits split beam monitoring at a higher volume tlian has been hitherto available in portable recording systems. New type high-speed power level indicators supply the visual means of checking transmission volume, these meters operating with remarkable rapidity, and practically no ballistic overswing. Plate currents and filament and power supply voltages are read on "percentage" calibrated meters, with rotary switches to select the desired circuits. A meter shunt in each circuit is so arranged that the normal meter reading is 100 per cent., irrespective of the magnitude of current or voltage undergoing test. Improved type carrier operated noise reduction is employed. This unit utilises new types of valves, pentodes, and duplex diode triode, replacing the straight triodes and copper oxide rectifier formerly used. Four units are used to accommodate the apparatus so far described, these being the Pick-Up Unit, Main Amplifier, Recorder Control and Noise Reduction. All units are contained in sturdy duralumin cases provided with either carrying handles or removable straps. Front panels are finished anodized grey and a judicious use of chromium on the fittings and for indicator bars inserted in the black control knobs adds a very pleasing finish. All valves are of the heater type and may be operated either from light weight portable 12volt batteries and banks of 180-volt dry batteries mounted in suitable carrying WESTERN ELECTRIC "QB." PORTABLE RECORDING CHANNEL. cases, or from 110volt A.C. power supply when this is available. Portable power units are provided to supply the necessary rectification and filtering for A.C. operation. The recorder is the standard studio type machine, modified for portable operation and provided with a duralumin carrying case. Permanent magnet light valves are used and the split beam photo-electric cell monitoring unit is an integral part of the recorder. Twelve volt D.C. interlocking motors are supplied for driving the recorder and cameras and also an alternative type of recorder motor which operates from the studio motor interlock system. A portable distri]:)utor motor and speed regulating cabinet ensures extremely accurate speed regulation and synchronisation of the twelve volt motors. Contracts have been obtained for the installation of the H" type transportable equipments aboard four ships {Continued at foot of next page).