JBL SA750, Руководство пользователя

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EN-19
SA750 DIGITAL FILTERS
The SA750 allows the listener to choose between
a number of digital filters for use in the audio
DAC. Digital filters are required to minimise
unwanted antialiasing distortion in the audio band
but no digital filter is perfect, all are a compromise
between various parameters. These include:
Frequency response – Audio level with respect to
frequency. Ideally this should not vary significantly
between 20Hz and 20kHz.
Phase – The time delay introduced between
reproducing different frequencies within the pass
band of the filter. Ideally this would be as low as
possible (linear phase).
Pre ringing – Additional audio artefacts that
precede the original audio impulse. These are
sometimes thought to be bad as this phenomenon
does not exist in the natural world, so ideally this
should be as low level and last for as short a time
as possible.
Post ringing – Additional audio artefacts that
follow the original audio impulse. Ideally these
should be as low in level and last for as short a
time as possible.
Aliasing – Additional audio artefacts introduced
into the audio band from high frequency signals.
We have chosen our default filter through
a combination of careful measurement and
listening tests and we believe they are the
best compromise to achieve the best listening
experience. However, all of the filters sacrifice
performance of one parameter to improve
another. Therefore, dependant on your choice of
listening material and personal preference, you
may wish to choose one of the other options. Note
that any audible differences are most likely to be
heard with sample rates of 48kHz and below.
Brick Wall (B Wall)
No phase shift, but introduces both pre and post
ringing artefacts.
Corrected Minimum Phase Fast Roll
Off (Corr MinP)
Low pre-ringing and the phase response varies
at higher frequencies. There is more post ringing
compared with linear phase and apodizing filters.
Apodizing (Default)
A compromise between phase, frequency
response and ringing. Its main advantage is that
it removes most of the ringing that has been
introduced upstream in the recording process
when the original material was recorded and
mastered.
Minimum Phase Slow Roll Off (MinP
Slow)
No pre-ringing artefacts but can introduce phase
shifts at higher frequencies. It has less post
ringing than the Minimum Phase Fast Roll Off,
but this is still higher than the linear phase filter
options. Very high frequencies in the last half
octave of the filter pass band will be slightly
attenuated.
Minimum Phase Fast Roll Off (MinP
Fast)
No pre-ringing and the phase response varies at
higher frequencies. There are significantly higher
amounts of post ringing compared with the linear
phase filter options.
Linear Phase Slow Roll Off (LinP
Slow)
Low and equal levels of pre and post ringing. No
phase shifts but can introduce high frequency
aliasing at a higher level than linear phase fast
roll off. Very high frequencies will be slightly
attenuated.
Linear Phase Fast Roll Off (LinP
Fast)
Higher and equal levels of pre and post ringing
compared with linear phase slow roll off. No
phase shifts and with minimal high frequency
aliasing compared with slow roll off.