PCM 録音装置の試作(第 2 報) : 再生系回路と総合特性

概要

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A PCM audio recording adapter which can be used in conjunction with the herical scanning type VTR has been constructed. This report describes the design of its playback part and the estimated overall characteristics throughout the recording and playback system. The digital code reproduced from the VTR is composed of the 12 bits PCM code and the 4 check bits for each sampled data. After serial to parallel conversion of each data and code error checking, the net 12 PCM bits are stored to the FI/FO register having a capacity of 12 bits×64 stages for each channel. The stored PCM bits are read out successively in the constant PCM sampling rate of 44.1kHz and converted to the analoge signal by a usual current ladder type D/A converter. The final playback signal is obtained pathing through the following output low path filter. The overall audio record-playback characteristics were estimated with respect to, for example, the frequency response, dynamic range, wave distortion, and impulsive noise caused by the code error. Nearly flat playback response ranging from zero to 19kHz and the dynamic range of about 70dB were obtained. The impulsive noise in the playback signal, however, was not sufficiently eliminated and the necessity of more complicated counterplan was confirmed to overcome the burst code error.
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