Filter 1 (Standard Fir Filter); Filter 2 (Short Fir Filter); Filter 3 (Bezier Interpolator Plus Iir Filter); Filter 4 (Poor Bezier Interpolator) - T+A CD 820 M Betriebsanleitung

Standard FIR filter)
Filter 1 (
The long FIR filter is the standard oversampling process
in digital technology, offering extremely linear frequency
response, very
characteristics
disadvantage is the pre- and post-echoes which are
added to the signal. These „time range errors" tend to
affect the music signal's dynamics, precision and
naturalness, and reduce spatial orientation.
Frequency response and transient characteristics of
the long FIR filter

Filter 2 (short FIR filter)

Shortening the filter (lower coefficient) reduces the time
range errors, albeit combined with a slight loss of
linearity in
performance.
Frequency response and transient characteristics of
the short FIR filter

Filter 3 (Bezier interpolator plus IIR filter)

In this process an ideal Bezier interpolator is combined
with what is known as an IIR filter. This eliminates the
problematic pre-echo of the FIR method. This process
produces highly „analogue" system characteristics, with
a sound quality and measured performance similar to
those of good analogue disc players.
Frequency response and transient characteristics of
the Bezier interpolator plus IIR filter
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high damping, linear
and constant group delays.
the frequency range and
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Filter 4 (pure Bezier interpolator)
This process delivers a perfect reconstruction of the
original music signal. It exhibits no pre- or post-echoes of
phase any kind, and does not add coloration or timing errors to
The the original signal. In sonic terms this method offers an
impressive blend of naturalness, good dynamics and
accuracy. This is our preferred process due to its
advantages in respect of sound, and is the basic
(default) setting of the CD 820 M.
Frequency response and transient characteristics of the
Bezier interpolator

Filter 5 (Bezier interpolator plus Noise-Shaping)

In this variant what is known as „noise-shaping" is added
after the ideal Bezier algorithm. This supplementary
damping stage further reduces the basic hiss in the audible range.
With certain types of material (e.g. classical music with a
very wide dynamic range) this can be an additional
advantage, but does result in a slight loss in precision
compared with the „pure" Bezier process.
Frequency response and transient characteristics of
the Bezier interpolator plus noise-shaping
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