Thanks.
And yet, dCS are willing to implement technical compromises.
From their measurement link:
Filter Performance
Digital audio is full of trade-offs. Which trade-off is best in terms of filter choice? Unfortunately, there is no “perfect” filter that will be optimum for all recordings. In essence the DAC filter you use affects amplitude response, phase response (transient performance) and image rejection.
For example, recordings made with poor filtering and lots of HF noise are likely to be improved with an asymmetrical filter, whereas those with good filtering will not cause the reconstruction filter to ring, and so the phase shift is unnecessary. At dCS we believe that it is therefore important to offer a choice of filters, so that the user can choose a solution to suit their music and tastes.
This variety of filter options means it is important to measure the flat signal bandwidth, the cut-off frequency and the image (or alias) rejection. It is also worth noting that filter characteristics become less of a factor at higher sample rates.
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In their manuals, they recommend different filters for different kinds of music. From the dCS Vivaldi v 2 manual, p. 37:
The first 4 PCM filters give different trade-offs between the Nyquist image rejection and the phase response. Filter 1 has the best rejection of (unwanted) Nyquist images and the sharpest roll-off, resulting in the poorest transient response of the four. Filters 2, 3 and 4 have progressively more relaxed image rejection and progressively better transient response. Filter 2 is often preferred for orchestral music, while Filter 3 and Filter 4 are often used for rock music.
Mike Moffat on the other hand offers a single time- and frequency-domain optimized digital filter in the Yggdrasil. No technical compromises deemed necessary.