(China Intellectual Property Office Patent No.201520212711.5)
Generated signals from piano, percussion and guitar contain a large amount pulse
wave. Studies of the sound psychology indicate that our ears are very sensitive to
the pre-ring of impulse wave. It makes music incoherent and unnatural. The
pre-ring, brought by FIR (finite impulse response) digital filters used in traditional
digital to analog conversion, can be tested and heard very easily. The Questyle
Audio CMA800i has the most advanced IIR digital filter, which completely
eliminates the pre-ring from the impulse wave and brings the most natural sound.
dCS is an example of a company using IIR digital filter technology.
Different digital filters have different impulse responses and group delay, creating
different subjective listening experiences. On the front panel of CMA800i, there is a
DFR button providing 5 different digital filters for user to choose. Among the five
digital filters, the pulse responses of IIR and FIR are totally different. Different FIR
or IIR digital filters have different frequency responses. The digital filters are
switchable based on user’s favorite.
Vibrating objects in nature produce a sound wave which has similar features to the
IIR digital filter. There is no pre-ring before the vibration and the vibration amplitude
decreases gradually after the vibration.
PCM Version Digital Filters
08
09
CMA800i IIR digital filter pulse response
CMA800i FIR digital filter pulse response
When the sample rate is as low as in 44.1k or 48k, the 5 digital filter options of the
Questyle Audio CMA800i will be:
-
IIR Apodisting
-
IIR soft-knee
-
IIR Half-band
-
FIR Apodisting
-
FIR Half-band
When the sample rate is as high as in 88.2k, 96k or 192kHz, the 5 digital filter
options of the Questyle Audio CMA800i will be:
-
IIR Apodisting
-
IIR soft-knee
-
FIR soft-knee
-
FIR Apodisting
-
FIR Brickwall
The Questyle Audio CMA800i will divide the user’s configuration of digital filters
into high and low groups and memorize the sample rate.
