Journal of the Society of Motion Picture Engineers ( Volume: 37, Issue: 12, December 1941)

[ACTIVE]

On the Playback Loss in the Reproduction of Phonograph Records

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Publisher: SMPTE — White Plains, NY, USA
Doc Type: Journal Article
Content Type: Original Research
Abbreviated Title: J SMPE
Volume: 37, No. 12, pp. 569–590
Abstract: A theory is set forth to explain the well known level losses, in particular of the upper frequency range, occurring in the reproduction of lateral-cut records. The performance of a pick-up stylus with a spherical point, riding in a laterally modulated record groove, is discussed from the point of view of the elastic properties of the record material. After introducing certain permissible simplifications, the elastic deformations of the two supporting groove walls are calculated, under the influence of the steady vertical pick-up force, the stylus inertia, and the stylus stiffness. Due to the fact that both forces and geometry are different on the two walls the respective elastic deformations are also found to be different for both walls. This fact results in a displacement of the pick-up stylus from the position which it would assume in an ideally rigid record groove and is responsible for the difference between the reproduced amplitude and the recorded one. Playback loss and translation loss are thus explained and quantitatively predicted. The discussion of the loss equation leads to a number of conclusions. It is found that in contradistinction to a theoretical pick-up with infinitely small vertical force and stylus impedance, it appears advisable to provide a practical pick-up with a definite stylus mass, in order to counteract effectively the playback loss due to the steady vertical force. The translation loss can thus be reduced to zero in systems with constant groove velocity if the pick-up constants—in particular, the stylus mass—are properly chosen. In systems with variable groove velocity (standard disk recording) the translation loss can not be made to vanish but an increase in the absolute playback level of the upper frequency range can be achieved, thus improving the signal-to-noise ratio.
Publication Date: 1941-12-01
DOI: 10.5594/J09946
ISSN: Print: 0097-5834
Link: https://doi.org/10.5594/J09946
Author(s): O. KorneiThe Brush Development Co., Cleveland, Ohio.
Copyright: © 1941 Society of Motion Picture and Television Engineers, Inc.

Bibliographic Reference(s)

1 Pierce J. A. Hunt F. V. : “Distortion in Sound Reproduction from Phonograph Records,” J. Soc. Mot. Pict. Eng. , XXXI (Aug., 1938 ), p. 157 . EXTERNAL
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13 Guttwein G. : “On the Linear and Non-Linear Distortions in Disc Recording,” Akust. Zeits ., V (Dec., 1940 ), p. 330 . EXTERNAL
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16 Timoshenko S. : “Theory of Elasticity,” McGraw-Hill Book Co. , New York ( 1934 ), p. 344 . EXTERNAL
17 Roark R. J. : “Formulas for Stress and Strain,” McGraw-Hill Book Co. , New York ( 1938 ), p. 245 . The expression for the factor k, erroneous in this book, is given correctly in this paper (see eq. 5). EXTERNAL
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2 Lewis W. D. Hunt F. V. : “A Theory of Tracing Distortion in Sound Reproduction from Phonograph Records,” J. Acoust. Soc. Amer. , XII (Jan., 1941 ), p. 348 . EXTERNAL
3 Löfgren E. : “On the Non-Linear Distortion in the Reproduction of Phonograph Records Caused by Angular Deviation of the Pick-Up Arm,” Akust. Zeits. , III ( 1938 ), p. 350 . EXTERNAL
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O. Kornei; On the Playback Loss in the Reproduction of Phonograph Records, Journal of the Society of Motion Picture Engineers ( Volume: 37, Issue: 12, December 1941); SMPTE, 1941. Available at https://doi.org/10.5594/J09946

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O. Kornei; On the Playback Loss in the Reproduction of Phonograph Records, Journal of the Society of Motion Picture Engineers ( Volume: 37, Issue: 12, December 1941); SMPTE, 1941. Available at https://doi.org/10.5594/J09946

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<span class="citation">O. Kornei; <cite>On the Playback Loss in the Reproduction of Phonograph Records</cite>, Journal of the Society of Motion Picture Engineers ( Volume: 37, Issue: 12, December 1941); SMPTE, 1941. Available at <a href="https://doi.org/10.5594/J09946" target="_blank" rel="noopener">https://doi.org/10.5594/J09946</a></span>

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<li>
O. Kornei; <cite id="bib-10-5594-j09946">On the Playback Loss in the Reproduction of Phonograph Records</cite>, Journal of the Society of Motion Picture Engineers ( Volume: 37, Issue: 12, December 1941); SMPTE, 1941
<span class="doi">10.5594/J09946</span>
</li>