User's Manual

User’s Guide ADI-2 DAC v2.2 © RME
57
SD LD (Short Delay Low Dispersion)
In theory, a filter should have as little phase deviation as possible over the frequency range,
have as short a settling time as possible, an acceptable decay time, and provide the maximum
possible frequency range without deviation. The stopband attenuation should be high to prevent
aliasing. A latency as low as possible would extend the application possibilities to more than
just listening to music.
The filter with the bulky name Short Delay
Low Dispersion approaches this ideal quite
well. It does not have the early treble
attenuation of the slow filters (see chapter
31.4), has a shorter settling time than Slow,
an average decay time like Sharp, a phase
maximum of only 9° at late 18 kHz (basically
phase-linear in the audible range), and a
latency of only 10 samples, so that it is also
well suited for professional real-time
monitoring. This makes it much more than
just a successful compromise.
31.5 DA Filter Curves 44.1 kHz
Note
: Sharp/SD Sharp and Slow/SD Slow are practically congruent. NOS shows a very early
drop. SD Low Dispersion is almost as linear as Sharp/SD Sharp.