A Digital Audio Time-Base Corrector for Linear Magnetic Recording

Audio time-base correction is an encode/decode process designed to electronically eliminate tape-path azimuth error and the resultant mono sum losses. Flutter is reduced to inaudible levels. A 19-kHz carrier signal is 60% amplitude-modulated by a 300-Hz sinusoidal waveform. This AM pilot signal is encoded onto the left and right audio tracks at −27 dB related to 160-nW/m fluxivity. When an encoded tape is replayed through the complementary decoder, the phase difference between left and right pilot signals is detected and used to servo one of two voltage-controlled digital audio delay lines. The relative left-right delay is adjusted to eliminate phase error. FM components of the pilot signal are demodulated with a phase-locked-loop decoder. The resultant error signal is used to servo both delay lines, significantly reducing flutter. The end result is a clearly audible improvement in reproduction quality.

Print ISSN

0036-1682

Published

1985-11

Content type

Original Research

DOI

10.5594/J03347