Recorder, Mechanical

a device for converting electrical signals into the mechanical vibrations of a stylus that cuts a groove in a recording medium during mechanical sound recording, particularly for the purpose of manufacturing phonograph records. Dynamic recorders are the most common type.

Figure 1. Diagram of a dynamic recorder for lateral monophonic sound recording: (1) permanent magnet, (2) magnet system poles, (3) connecting cone with a slot (7) cut out (flat spring of the recorder’s vibrating system), (4) ring of magnetically soft material, (5) rod on which the recorder is mounted, (6) driving coil, to which the recording signal is fed, (8) copper ring that serves as a shield to reduce inductive coupling between the driving coil and the electromagnetic feedback coil (9), which corrects the frequency response of the recorder’s vibrating system, (10) sapphire cutter, (11) lightweight shell of the vibrating system, (12) support ring

The structure of a dynamic recorder for monophonic sound recording is shown in Figure 1. A dynamic recorder for stereophonic sound recording is basically a duplex monophonic recorder in which both parts of the moving system are balanced by means of a transverse beam (Figure 2). The principal technical parameters of a mechanical recorder are an operating fre-

Figure 2. Diagram of the vibrating system of a stereophonic recorder: (1) sapphire cutter, (2) transverse beam (the cutter vibrates relative to point A when the right-hand part of the vibrating system is being driven, and relative to point B when the left-hand part of the vibrating system is being driven), (3) and (4) left-hand and right-hand parts of the vibrating system, (L) distance between the left-hand and right-hand parts of the vibrating system, (C) cutter point

quency range of 50 to 30,000 hertz, a nominal power up to several tens of watts, a nonlinear distortion rating (at nominal power) of < 1 percent, and a minimum crosstalk attenuation between channels (for stereophonic recording) of 35 decibels.