速度帰還をかけたトーンアーム

概要

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The mechanical resonance of a tone-arm system, arising in a frequency range between 5Hz and 10Hz, causes deterioration of sound quality. The peak level of the reasonance reachs to 10dB. The tone-arm, furnished with velocity sensors and linear motors, is developed in order to damp the resonance. Perpendicular and horizontal movement of the tone-arm is detected independently by corresponding velocity sensors. Detected signals of each sensor are amplified and fed back to each linear motor. Motion of the tone-arm is controled by these linear motors. As the result, the sound quality is improved greatly because the peak level of the resonance is suppressed by negative feedback (velocity feedback) gain. Moving speed of the tone-arm is controled to be uniform and stable. The transfer function of the tone-arm motion and its equivalent circuits. The damping factor ζ , which is related to equivalent viscosity resistance, and the corner angular frequency ω_0, on first order lead elements involved in the equation, are calculated with an aid of the negative feedback gain R_2/R_1. If R_2/R_1 increases, gain level rises at very low frequencies bacause ω_0 moves to high frequencies. In this system, the best sound quality is obtained when R_2/R_1=100〜400. Peak level of the resonance and f^`_0(ω^`_0/2π) are 6. 5〜2dB and 1. 08〜4. 32Hz respectively, for this case.
社団法人日本音響学会の論文
1981-03-01