Physicists Here Invent Phonograph Pick-up 5 Times Lighter Than Others

Invention of a new electric phonograph pick-up that is from 5 to 15 times lighter than the types now in use has been made by two men working in the Cruft Laboratory here. The inventors are Frank V. Hunt, assistant professor of Physics and Communicating Engineering, and J. A. Pierce.

The new pick-up pressure on the record is only 0.176 ounces while that of the ordinary pick-up is from one to three ounces. It is an inductor dynamic type with a permanent sapphire needle on a single-loop, U-shaped inductor in a strong magnetic field.

Faced with the task of recording the exercises of the Tercentenary on a special long-lasting material for historical purposes, Hunt and Pierce discovered that a heavy pick-up would damage the sensitive acetate records.

Another disadvantage was in the extremely high frequencies of the records which a rigidly fixed needle would miss. In the new pick-up the needle is fixed in a rubbery substance allowing it to receive delicately modulated vibrations.

Whereas the old heavy type of pick-up had to be moved with care so as not to run radially over the surface of the record, the new one can be slid across the surface without leaving the faintest trace of its path.

This was particularly important on the comparatively soft records which were used for the Tercentenary records.

The only draw-back now is that the pick-up is now 20 to 30 decibels less sensitive than the usual type, but this can be remedied, the inventors say.