The Application of Negative Feedback to Electromechanical Devices
C. F. Wiebusch, L. Vieth · The Journal of the Acoustical Society of America · 1938
The elementary theory of feedback as applied to electromechanical transducers is discussed. Provided the conditions for stability are met, the feedback will produce a flat velocity vs. frequency characteristic; reduce the phase shift, noise, and nonlinear distortion normally introduced in the amplifier and the transducer; and will increase the output mechanical impedance of the transducer. A disk recorder embodying this principle is described. The new recorder is capable of recording on wax or direct recording material without appreciable effect on its characteristics which include a uniform response from 30 to 12,000 cycles and exceptional freedom from distortion products.