Operation Manual

Appendix 4 –Resolution Enhancement 51
518 User Guide
Figure 3. Showing the audibility of noise in the LP system for
comparison with digital channels.
Dynamic-range optimisation with Gain
The noise-floor of a digital system is determined absolutely by the lowest
preceding wordsize. For nearly all commercial material this is 16 bits.
518 allows you to get the best out of whatever comes next, by making
sure that the full output capability is used. Gain can be used in Resolution
Enhancement and Mastering to boost the level of the signal to fill the
available capacity.
For some reason, many CDs are recorded well below maximum level. By
boosting these we are able to reduce the audible effect of noise in
subsequent processing, or digital filters in DACs, or in the analogue
electronics.
Getting this right is easy – 518 immediately tells you if had to 'clip' the
output because you asked for too much. See page 18.
Dynamic-range optimisation with Pre-emphasis
Real-world music and speech signals do not have equal energy at all
frequencies. Typically the loudest sounds happen in the mid-range and
peak levels are much reduced above 5kHz.
This fact has been exploited extensively in audio systems over the years,
with a system known as pre-emphasis.
Pre-emphasis Channel De-emphasisInput
Using Pre-emphasis and de-emphasis to improve channel performance
The diagram above shows the general pre-emphasis method. To take
best advantage of the channel – which could be an AM or FM radio link,
an LP record, a tape recording, a CD or a DAC – high-frequency signals