Esp1
2004-07-08 08:14:42 UTC
http://surroundpro.com/articles/publish/inside_surround/article_203.shtml
"for DSD this noise (ultrassonisk støy min merknad) is transferred to the
disc, and there are potential systems issues that can arise when this
high-frequency noise is converted into the analog domain and applied to an
audio amplifier and speaker.
These issues can include slew rate limiting in the amplifier stages as well
as inter-modulation distortion and damage to the high-frequency drivers in
loudspeakers. Philips Electronics and Sony Corp. recognize and address this
issue in a document titled "Super Audio CD System Description." This
document, commonly referred to in the audio industry as the Scarlet Book, is
the defining document for Super Audio CD standards and systems requirements.
Part 2, Annex E of this document recommends that, for protection of analog
loudspeakers and amplifiers, a SACD player employ an analog low-pass filter
with a cut-off frequency of 50 kHz and a minimum 30 dB per octave slope
(though this bandwidth recommendation is relaxed for wide-band audio gear).
Unfortunately, this recommended analog filter has several potential pitfalls
that include the frequency and phase response variations that result from
standard component tolerances, additional circuit complexity, potential
performance degradation, and increased cost. The systems designer must also
determine if this analog filter is to remain within the signal path when the
system is operating in a high-sample rate PCM mode, such DVD-A at 192 kHz
sample rate. If the decision is to remove the filter, an additional cost is
incurred to provide the required switching circuitry and control logic, as
well as a risk of degrading sonic quality with this additional circuitry in
the signal path.
The overwhelming majority of digital-to-analog converters that are capable
of converting DSD require an external analog filter to meet the Scarlet Book
recommendations. Fortunately there is another option. Since this noise
originates in the DSD recording process and is present in the digital
domain, it is feasible that the 50 kHz filter can be implemented digitally
to meet the goal of protecting analog amplifiers and speakers."
"for DSD this noise (ultrassonisk støy min merknad) is transferred to the
disc, and there are potential systems issues that can arise when this
high-frequency noise is converted into the analog domain and applied to an
audio amplifier and speaker.
These issues can include slew rate limiting in the amplifier stages as well
as inter-modulation distortion and damage to the high-frequency drivers in
loudspeakers. Philips Electronics and Sony Corp. recognize and address this
issue in a document titled "Super Audio CD System Description." This
document, commonly referred to in the audio industry as the Scarlet Book, is
the defining document for Super Audio CD standards and systems requirements.
Part 2, Annex E of this document recommends that, for protection of analog
loudspeakers and amplifiers, a SACD player employ an analog low-pass filter
with a cut-off frequency of 50 kHz and a minimum 30 dB per octave slope
(though this bandwidth recommendation is relaxed for wide-band audio gear).
Unfortunately, this recommended analog filter has several potential pitfalls
that include the frequency and phase response variations that result from
standard component tolerances, additional circuit complexity, potential
performance degradation, and increased cost. The systems designer must also
determine if this analog filter is to remain within the signal path when the
system is operating in a high-sample rate PCM mode, such DVD-A at 192 kHz
sample rate. If the decision is to remove the filter, an additional cost is
incurred to provide the required switching circuitry and control logic, as
well as a risk of degrading sonic quality with this additional circuitry in
the signal path.
The overwhelming majority of digital-to-analog converters that are capable
of converting DSD require an external analog filter to meet the Scarlet Book
recommendations. Fortunately there is another option. Since this noise
originates in the DSD recording process and is present in the digital
domain, it is feasible that the 50 kHz filter can be implemented digitally
to meet the goal of protecting analog amplifiers and speakers."