Digitalized Audio Recording Adapter Utilizing Delta Modulation Method (2nd Report) : On the Playback System and Overall Characteristics

A digitalized audio recording adapter utilizing adaptive delta modulator for A/D conversion was trially manufactured. This report describes the design of its playback part and estimated overall record-playback characteristics. The digital code reproduced from recording VTR includes 150 serial data bits for each horizontal scanning period. After serial to parallel conversion, the data bits are written to the buffer memory in intermittent mode, and read out from it in continuous mode. Read out data are then added to adaptive delta demodulator. Adaptive delta demodulator performs parallel to serial conversion in 1.1025 Mbit/s serial rate and D/A conversion. Measured overall frequency response gave flat curve under the designed demodulator cut off frequency of 8kHz at the critical overload input level, and 6 dB/oct. dropping characteristics under the cut off frequency. Signal to noise ratio was about 62dB in low frequency range.