DFs with skills (wonderboys...)

[210]

What digital filters do you know
that can do not just what they have to
but special sound enhancements with digital data.

I know the SM5845 that "alpha-processes" 16bits to 20bits
and the KAN06 that "d.r.i.v.e.s" 16bits to 24bits.

I guess, they are easier to use for diy'ers than DSPs.

[Ken Newton]

As far as external DF chips are concerned, there was the PMD100 from Pacific Microsonics which featured a HDCD decoder, along with a number of dithering options. Unfortunately, the PMD100 is long since out of production. You may be able to salvage one from one of the older DACs featuring it. The Burr-Brown DF1704 and DF1706 feature a selectable slow-roll off filter corner option. This feature trades maximum freaquency response extension for improved transient response.

Of course, most digital filters are now integrated within the DAC chips. Among those you'll find that nearly all feature at least two selectable corner roll-off slopes. The Wolfson DACs, probably feature the greatest number of DF options which include some minimum-phase filter responses.

[Ken Newton]

By the way, the example of apparently increasing the sample word size you mention is merely an side effect of the mathematical process by which interpolating DFs work. The extra bits allow the filter to provide improved stop-band attenuation, but that is not a significant problem in digital audio playback.

[210]

Thanks Ken!

The "Alpha" has probably to do with the mathmatics of the data process,
maybe they had called it "Delta" if it minimizes someting,
so it maybe 'spreads the entropie of information' or stuff like that.

"D.R.I.V.E." is maybe a more practical startup (Ansatz).
As far as I remember it splits the data with a 3 kHz and 8kHz digital filter (function)
and then recombine it with the original data (additional or by multiplying)
to get the wanted coefficients. It's desribed somewhere in my data backups...

The PCM1794 also offers two different roll offs,
but with Denons DC710AE cdp they are not selectable.

Even the new DACs have integrated DFs,
it's maybe possible to use these old proprietary 'wonderboys'
to feed modern DACs. The usage of the filter ic's can
be seen in the service manuals. Jitter is maybe a problem.

Regards,