USB Digital Microscope: How to use it to set 92 Degree Stylus Rake Angle (SRA)

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The stylus rake angle is the angle the stylus’s “contact patch” makes to the record surface. If you have a relatively inexpensive cartridge with a spherical stylus you don’t have to worry about SRA because the contact area remains the same regardless of arm height. On the other hand, elliptical styli along with the more severe “line contact,” Shibata, Geiger, Ortofon and other long, narrow contact patch “cutting edge” (poor metaphor!) stylus profiles require careful SRA setting to perform as designed.These “severe” stylus profiles have the ability to more accurately trace the vertical modulations made by the sickle-like lacquer cutting stylus that is offset from true vertical and thus produces an angled cut, but if they are not properly aligned they bang into the vertical modulations rather than track them.

The more accurately the playback stylus replicates the cutter stylus angle, the less IM (Intermodulation Distortion) is produced, resulting in smoother yet far more detailed sound. Setting SRA by “ear” usually meant going from brighter, harder sound when set too high, to duller, thicker and less focused sound when set too low.

Once we began examining styli under the microscope it became obvious that .....

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