Measurement of Spectral Content of Record Warps
Any design to obtain improved dynamic response of the cartridge-tone-arm system must include the very-low-frequency warp variations on the record surface. It is discussed how these signals can be best quantified through power spectral density functions for analytical use in tone-arm design. Using a minicomputer-based data acquisition system, a data base representing 220 records was obtained. The average and worst case power spectral densities for both vertical and horizontal warps are specifically presented. Both warp displacement and warp velocity are given. The horizontal variations are seen to reflect simply the center hole offset and are uncorrelated with the vertical warps. The worst case envelope for vertical warps is shown to be somewhat lower than that used by previous investigators. More importantly, the average vertical warp is seen to be an order of magnitude less than the worse case.
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