Audio DAC choice in CD players: Is a sigma-delta (ΔΣ) D/A converter the most likely DAC architecture used in a consumer CD player?

Difficulty: Easy

Correct Answer: Correct

Explanation:


Introduction / Context:
Consumer audio playback emphasizes high resolution, excellent linearity, and low noise at moderate bandwidths. Sigma-delta (ΔΣ) DACs excel here by oversampling and noise-shaping quantization noise out of the audible band, followed by digital filtering and simple analog reconstruction filters. The question checks whether this common industry practice is recognized.


Given Data / Assumptions:

  • Audio sample rates around 44.1 kHz and multiples (oversampling).
  • Emphasis on dynamic range and low distortion over extreme speed.
  • Mass-market integration and cost sensitivity.


Concept / Approach:
ΔΣ DACs convert a high-rate, low-bit-depth bitstream into analog using a simple analog filter, achieving high effective resolution through oversampling and noise-shaping. Their architecture suits audio CD playback (16-bit/44.1 kHz) and modern high-resolution formats, enabling excellent performance with economical analog filtering compared to multibit R-2R ladders that demand precise trimming and steep analog filters.


Step-by-Step Solution:

Optical pickup reads pits → digital PCM stream.Digital filtering/oversampling shapes noise out of band.ΔΣ DAC reconstructs analog with a gentle analog filter stage.


Verification / Alternative check:
Audio DAC datasheets for consumer CD and DVD players over the past decades predominantly feature sigma-delta architectures due to their cost-performance advantage.


Why Other Options Are Wrong:

“Incorrect”: Contradicts widespread industry usage.“Only for 24-bit” / “only portable”: Architecture applies broadly across bit-depths and product types.Optical pickup details do not determine DAC architecture choice.


Common Pitfalls:
Assuming R-2R ladders dominate audio; while used in high-end niches, ΔΣ is the mainstream choice.


Final Answer:
Correct

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