Meridian America Meridian 518 manual Appendix 2 Hints on Mastering

Appendix 2 – Hints on Mastering 47

dynamic range is extended. Implicit in this theory is the fact that the digital channel has near-infinite differential linearity, i.e. each bit has a magnitude precisely twice or half the magnitude of the next.

When this signal is applied to a D/A converter some problems may arise. First the D/A process may be associated with an oversampling digital filter. Commonly these parts take no precautions with regard to dither and introduce a quantisation noise-floor themselves at the approximate level of the LSB in the filter, thereby obliterating lower-level information in the signal. Secondly the D/A converter will not have perfect differential linearity – there is no longer any reason why successive bits will maintain a precise 2:1 ratio. The effect of this is also equivalent to quantisation at the linearity level of the converter.

In summary therefore, the wide subjective dynamic range inherent in the recording cannot be reproduced unless the replay D/A system has both a word-size (in terms of associated oversampling filters) and a differential linearity equivalent to the original material, which in this example was 20 bit. The result would be further improved by the correct use of dither and noise-shaping in the digital filter.

That a subjective channel dynamic range of approaching 20 bit can be conveyed on a 16 bit channel is quite remarkable. On reflection, it should not be surprising that to realise this benefit, both the A/D and D/A sub- systems must have the required 20-bit precision.

518 User Guide