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Delta-sigma (ΔΣ; or sigma-delta, ΣΔ) modulation is an oversampling method for encoding signals into low bit depth digital signals at a very high sample-frequency as part of the process of delta-sigma analog-to-digital converters (ADCs) and digital-to-analog converters (DACs).
A 1-bit DAC (sometimes called Bitstream converter by Philips) is a consumer electronics marketing term describing an oversampling digital-to-analog converter (DAC) that uses a digital noise shaping delta-sigma modulator operating at many multiples of the sampling frequency that outputs to an actual 1-bit DAC (which could be fully differential to minimize crosstalk). [1]
A delta-sigma ADC (also known as a sigma-delta ADC) is based on a negative feedback loop with an analog filter and low resolution (often 1 bit) but high sampling rate ADC and DAC. The feedback loop continuously corrects accumulated quantization errors and performs noise shaping : quantization noise is reduced in the low frequencies of interest ...
Oversampling DACs or interpolating DACs such as those employing delta-sigma modulation, use a pulse density conversion technique with oversampling. Audio delta-sigma DACs are sold with 384 kHz sampling rate and quoted 24-bit resolution, though quality is lower due to inherent noise (see § Figures of merit).
The Nintendo Entertainment System's audio processing unit (the Ricoh 2A03 chip) includes a Delta Modulation Channel (DMC) to demodulate percussion and sound effects. The DMC reads delta-encoded audio data via direct memory access into a shift register, which gets shifted out serially into an up/down counter acting as the demodulator's ...
By running these converters at some multiple of the target sampling rate, and low-pass filtering the oversampled signal down to half the target sampling rate, a final result with less noise (over the entire band of the converter) can be obtained. Delta-sigma converters use a technique called noise shaping to move the quantization noise to the ...
This results in a broadband dynamic range of only 7.78 dB, but it is not consistent among frequency bands, and in the lowest frequencies (the audible range) the dynamic range is much greater — over 100 dB. Noise shaping is inherently built into the delta-sigma modulators. The 1-bit converter is the basis of the DSD format by Sony.
The successive-approximation analog-to-digital converter circuit typically contains four chief subcircuits: . A sample-and-hold circuit that acquires the input voltage V in.; An analog voltage comparator that compares V in to the output of a digital-to-analog converter (DAC).