Outboard DACs

Already implemented in Matrix Audio's Element X [HFN Jan '21] and X-Sabre Pro [HFN Nov '17], the ES9038Pro converter offers the designer seven alternate digital filter modes - five with 'fast' (sharp) roll-off characteristics and two with 'slow' (gentler) treble roll-offs. In this instance, however, MA's menu has the filters rather jumbled up... In sequence, 'Fast Minimum' is 'Apodising'; 'Slow Minimum' is 'Slow Linear'; 'Fast Linear' is 'Brickwall'; 'Slow Linear' is 'Hybrid'; 'Brickwall is 'Fast Minimum'; 'Hybrid' is 'Slow Minimum' and 'Apodising' is 'Fast Linear'. Either way, the frequency response, stopband rejection and time-domain distortion all depend on which digital filter is chosen.

The Fast Minimum, Fast Linear [black traces, inset Graph], Apodising and Brickwall all have sharp roll-offs [the Hybrid filter, blue, has a steep but early roll-off], with Slow Minimum [red] and Slow Linear offering gentler treble roll-offs, reduced 'ringing' but poorer stopband rejection. Otherwise, those first five filters offer a similar 73-84dB rejection of digital aliasing images with 48kHz media, falling to 14-18dB with the Slow filters - these are better suited to higher sample rates. With 48kHz files the responses reach out to -0.1dB, -0.0dB, -4.0dB, -4.0dB, -12.3dB, -5.0dB and -3.5dB/20kHz, respectively. With 96kHz media, the 45kHz response limits are -0.2dB, -0.5dB, -14dB, -7.6dB, -24dB, -7.2dB and -5.1dB while, with 192kHz files, the 90kHz response limits are -0.8dB, -1.0dB, -15dB, -8.1dB, -24dB, -7.7dB and -5.6dB. PM