5.5.1 Introduction

5.5.1.1 Under optimum conditions digital tapes can produce an unaltered copy of the recorded signal, however any uncorrected errors in the replay process will be permanently recorded in the new copy or sometimes, unnecessary interpolations will be incorporated into the archived data, neither of which is desirable. Optimisation of the transfer process will ensure that the data transferred most closely equates to the information on the original carrier. As a general principle, the originals should always be kept for possible future re-consultation however, for two simple practical reasons any transfer should extract the optimal signal from the best source copy. Firstly, the original carrier may deteriorate, and future replay may not achieve the same quality, or may in fact become impossible, and secondly, signal extraction is such a time consuming effort that financial considerations call for an optimisation at the first attempt.

5.5.1.2 Magnetic tape carriers of digital information have been used in the data industry since the 1960s, however, their use as an audio carrier did not become common until the early 1980s. Systems reliant on encoding audio data and recording onto video tapes were first used for two track recording or as master tapes in the production of Compact Discs (CD). Many of these carriers are old in technical terms and in critical need of being transferred to more stable storage systems.

5.5.1.3 A crucial recommendation of all transfers of digital audio data is to carry out the entire process in the digital domain without recourse to conversion to analogue. This is relatively straightforward with later technologies which incorporate standardised interfaces for exchanging audio data, such as AES/ EBU or S/PDIF standards. Earlier technologies may require modification to achieve this ideal.