Projection engineering (Sept 1929-Nov 1930)

Page 50 Projection Engineering, September, 1929 BURT REPRODUCER FOR TALKING MOTION PICTURES The Burt Synchronous Reproducer illustrated is one of the simplest reproducers of talking motion pictures both film and disk which has appeared on the market. Synchronous Motor Drive (110 or 220 volts, 50 or 60 cycles). Prevents variation in speed from variation in line voltage, or projection load. The Super Cells used require only two stages in head amplifier, hence less distortion. Ease of Threading. When running disk or silent, the Sound-on-Pilm unit is not threaded. Sound-on-Film threads as easily as through a Powers gate. Turn Table is Accessible, being up high at the side of the machine. Easy to Install. Installation can be made by the ordinary operator, and wire man. Projector Head is driven by its main drive gear and is not required to drive any part of the sound equipment. Only Three Shafts: (1) Motor Drive, (2) Sound Film Shaft, (3) Disk Table Shaft. Variable Speed can be used for making schedule by driving the head off the Powers Motor, when running silent. Change from synchronous drive to variable speed drive requires about ten seconds. No Vniversals — No flexible couplings, flexible shafts, or long unsupported shafts are used, as these produce tremolo. Fire Hazard is Decreased by use of this equipment. Failure of take-up does not cause film to pile up in light. The photoelectric cells used have such a high output that only two stages of amplification are required in the head amplifier which feeds through the Fader directly into the power amplifier which may be any standard make of three-stage power amplifier. Two photoelectric cells are supplied with each head in one case, and in the event that one cell ceases to function the other may be put into operation by simply rotating the cell case one-half turn. No amplifier tubes are used in the cell case or on the machine itself. The wires from the photoelectric cells are brought out to a jack which plugs into the head amplifier. Another jack on the disk pickup arm plugs into the same head amplifier and thereafter control is had by means of the switch on top of the head amplifier. When this switch is in a vertical position everything is "off" ; when switched to the left the disk is connected to the Fader ; when switched to the right the head amplifier filaments are lighted and ^he Sound-on-Film pick-up is connected to the Fader. Manufactured by R. C. Burt Scientific Laboratories. 900-904 E. California Street, Pasadena, Calif. NEW JENSEN 10-INCH CONE DYNAMIC SPEAKER The new Jensen Concert Dynamic is to be built in four types for operation from 110 volt a-c. 110 volt d-c, 220 volt d-c. and 6 volt d-c. Jensen "Concert" Dynamic Speaker. The top price is $35 for the unit for operation from 110 volt a-c. This unit is equipped with a dry rectifier system and operates without perceptible hum from the alternating current. The models for operation from d-c will carry a list of $27.50. The new Concert speaker is to be offered also in the Jensen Imperial Cabinet which was announced earlier in the year. Equipped with the Concert Dynamic unit, the list prices have been set at $80 with the a-c. unit, and $72.50 with any one of the three d-c. units. ELLIS TWO-BUTTON MICROPHONE The Ellis Electrical Laboratory, 333 West Madison St., Chicago, have introduced a new two-button stretched diaphragm carbon granule microphone, known as Model No. 29. The carbon hiss which is characteristic of so many microphones is at an exceptionally low level. This microphone has no harmonics of its own and will give no distortion. It is of a rigid three-pillar construction and will therefore withstand rough handling, without losing its fine adjustment. A feature of this microphone is that sufficient sensitivity is obtainable for all practical purposes with a consumption of only 5 ma. at 3 volts. A factor of safety is provided by allowing 10 ma. to be used on each button without danger of burnout. This sensitivity is obtained without minimizing the carbon content or creating diaphragm resonance. Sufficient carbon is used to insure durability. Finished in either nickel or statuary bronze. Diameter, 3.4 inches ; overall thickness, 1.5 inches. Can be mounted in any standard stand. The list price of the Ellis Model No. 29 microphone is $70. NEW AMERICAN SILVERSHEET SOUND SCREEN The American Silversheet Co., of 800 Beaumont St., St. Louis, Mo., have perfected a new sound screen which is constructed of a specially jelled pyroxylin process which impregnates the surface into the material in such manner that in addition to the fact that this screen can be washed it also becomes scuff-proof. The screen is constructed with specially designed even-staggered perforations, for the passage of sound, but the perforations in no way interfere with the projected picture. The Burt Reproducer for Talking Motion Pictures NEW MELLAPHONE SPEEDOMETER The Mellaphone Corp. of Rochester, N. Y., makers of the Mellaphone sound picture apparatus, is now offering a speedometer for motion picture projection work. This new speedometer is guaranteed as to workmanship, durability and accuracy and is warranted to give complete satisfaction. The price of this new speedometer is $20 complete. Mellaphone is ready to make immediate quantity deliveries of the speedometer. NEW AMPLION DYNAMIC UNIT A giant dynamic loudspeaker unit of radically new design and very high efficiency has just been announced by the Amplion Corporation of America. The new unit is known as "type AA-102 — Improved Giant Dynamic" and displaces the older "AC-100" model. The magnetic field of the AA-102 has been reduced to two-thirds the size of the AC-100, although the flux density has been increased by 7 per cent. The weight of the unit has been decreased from twenty pounds to only fifteen pounds. The use of a special magnetic metal alloy makes possible this lighter weight and stronger magnetic field. An important new feature of the "Improved Amplion Giant Dynamic" unit is the composite diaphragm. The composite construction provides a double sound chamber above the diaphragm, which produces remarkable tone separation. The center of the diaphragm is convex, giving greater strength. Vanes radiate outward towards the periphery of the diaphragm. These furnish additional re-enforcement, preventing ripples which might create extraneous noises. The diaphragm is made of duraluminum, for extreme lightness. The voice coil is wound with fine copper wire and has an impedance of 8% ohms. Specially prepared flexible leads are used to bring connections to the binding posts, thus avoiding the possibility of coil breakage. The over-all dimensions of the unit are 5% inches in height by 6 inches in diameter. The lower portion of the unit is only 4% inches in diameter. The new Amplion "Giant Dynamic" unit, for theatre work. lUllllllllllllllllllllllllllllllllllllllllllllllf The type AA-102 Amplion unit has been developed especially for talking motion picture use, although it can be used to great advantage for all high volume public address work. It requires a field supply of 1.6 amperes at 6 volts d-c. For theatre work the unit is generally used with an Amplion M-10 exponential horn, having an air column ten feet in length. The new unit, in combination with the air-column horn has a wide response range and enormous volume with super-fine tone quality. SUPER-POWER CLAROSTAT The Super-Power Clarostat is a heavyduty adjustable resistor intended for all manner of applications calling for a precise resistance value. This device is based on the well-known Clarostat compression principle of obtaining stepless and noiseless resistance that remains set at any value desired. Thus the Super-Power Clarostat is at once a variable resistance when it is necessary to try different values, and a fixed resistance when the proper value has been found by actual test. For the various applications in radio as well as in electrical work, the SuperPower Clarostat is furnished in three resistance ranges, namely : Filament Range % — 10 ohms Low Range 25 — 50 ohms Universal Range . . . 100 — 100,000 ohms This device is built for heavy-duty service. It is capable of withstanding high temperatures when dissipating up to its Super-Power Clarostat.