The freedom from humidity and temperature limitations have made ferroelectric ceramics a valuable type of transducer for phonograph pickups (originally designed for 78 rpm records). Two groove sizes now indicate the use of dual styli. A pickup structure is described in which dual styli are used back-to-back on one lever. A mechanism is provided on the bottom of the pickup whereby the stylus assembly can be turned over to present the proper stylus to the record. This structure imposes no dynamical limitations on the performance of the pickup, as the additional mass required for the second stylus i.s only a small percentage of the total mass, and no additional stiffness constraints are imposed on the system.Reasonably flat characteristics have been obtained. In one commercial model a sensitivity of over one-half volt is achieved on microgroove records, with a frequency range to 10 000 cps with a tracking force of 6 grams for microgroove and 9 grams for standard-groove records.
RCA-Victor "Orthophonic" (microgroove) recording'characteristic, which is substantially identical to the proposed National Association of Radio and Television Broadcasters curve. Recording velocity and amplitude curves are shown. The solid branch A is the response for a 5 megohm value of R and the dashed branch B is Redistribution subject to ASA license or copyright; see http://acousticalsociety.org/content/terms. Download to IP: 141.
An instrument is described by which the velocity versus frequency characteristics of a conducting filament or similar vibratile member may be detected, regardless of the inaccessibility of the member. The assembly to be studied is submerged in a known magnetic field and subjected to vibration over the audio range. The voltage generated in the vibratile member is amplified and this indicates the integrated vibration velocity of the member.
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