20
DSD D/A Converter this low pass filter has to be implemented in the analog
domain which can be problematic because the non-linear phase characteristics of
such a filter. Alternatively this filter can be implemented in the digital domain
where the DSD signal is converted to PCM (at e.g. 176.4 kHz/24 bit) and at the
same time gets properly low pass filtered, e.g. with a linear phase filter which is
easily achievable in the digital domain.
A.3
DSD uses
The DSD format initially was conceived for distribution and archiving. Later on
it became more and more popular in music recording with its own set of problems
as described below. DSD shows the state of the art of the 90ies. The 1 bit
sigma-delta A/D and D/A converters were very popular at that time. Converter
techniques have progressed though. Today the modern sigma-delta converters
are multi-bit designs with e.g. 6 bits instead of 1 bit. This for good reasons of
course, the 1 bit technique has some inherent problems with dithering and idle
tones. If the SACD was conceived today, it would use a 6 bit format.
A.4
Processing
If a recording made in DSD has to be processed, e.g. the loudness has to be
adjusted or some equalizing is required, then the DSD signal has to be converted
to PCM in order to be able to do the processing. In the PCM format the signal
can be processed, i.e.
”
produced“ as required in order to get a final version. In
such a case it does not make sense to do a recording in DSD to start with. A
PCM recording at e.g. 88.2 kHz/24 bit would make much more sense. After the
production process the file can always be converted to DSD if required.
A.5
What is better?
The discussion whether DSD is better than PCM is moot. DSD is another
variant to store music, like PCM, MP3, magnetic tape, vinyl etc. All formats
are fine as long as there are people preferring one over the other for whatever
reasons. A matter of taste or practical reasons as with MP3 for instance.
A.6
The future
Technically speaking, PCM from like 88.2 kHz/24 bit up, is definitively better
than DSD. There are attempts to enhance DSD by rising the sampling rate from
2.8824 MHz to 5.6448 MHz or even 11.2896 MHz. Some problems of DSD may
be reduced with such measures, but the 1 bit quantization problem cannot be
eliminated. With the DSD downloads becoming more and more popular the
DSD format is going to stay with us. A niche, but a growing one.
Summary of Contents for INT204
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