Sony STR-DE845 Training Manual page 54

13. Super Audio Cd
Additionally, the effects of noise in the upper range can be eliminated by passing the signals through an analogue
low-pass filter at the time of playback. By incorporating ∆Σ modulation, the DSD format can achieve expanded
frequency characteristics and a greater audible dynamic range.
The ∆Σ modulator, as used in a real DSD system, has many high order feedback stages. Depending upon the
modulator's degree and circuit structure, the noise-shaping floor is determined. The ∆Σ modulator is an essential
technology for Super Audio CD. With the continuous improvements being made in this field, the playback sound
quality of the Super Audio CD format will enjoy even higher quality sound. With future advances of this specific
technology alone, the broad dynamic range that so characterizes the Super Audio CD format will be even more
of a reality.
Figure 13-8 shows a theoretical simulation of a very simplified ∆Σ modulation system. In principle, it is possible
to achieve an audio range and a dynamic range exceeding 120dB. With DSB, playback frequency characteristics
for the high frequency range can be extended up to approximately 1.4MHz. However, in the real world, in order
to reduce quantization noise, the characteristics are most commonly determined by a low-pass filter on the
player side at the time of playback, allowing for an optimum playback frequency range.
The playback frequency range of Super Audio CD features a smooth curve that accurately expresses the analogue
signal, allowing playback of signals that exceed 100kHz. On the other hand, the PCM frequency curve for CD
has severe drops, completely cutting off the playback signal. The difference in playback frequency for both
formats is therefore very noticeable.
10kHz SQUARE WAVE INPUT 10kHz SQUARE WAVE INPUT
44.1kHz/20-BIT OUTPUT (PCM)
DIRECT STREAM DIGITAL (DSD) OUTPUT
FIGURE 13-9 - REPRODUCTION OUTPUT DIFFERENCE FOR
A 10kHz SQUARE WAVEFORM
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