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Filter 1
(
Standard FIR
filter
)
The long FIR filter is the standard oversampling process
in digital technology, offering extremely linear frequency
response,
very
high
damping,
linear
phase
characteristics and constant group delays.
The
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 the frequency
range
and
damping
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
Filter 4
(pure
Bezier
interpolator)
This process delivers a perfect reconstruction of the
original music signal. It exhibits no pre- or post-echoes of
any kind, and does not add coloration or timing errors to
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
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