本帖最後由 bennetng 於 2018-8-28 22:26 編輯
2005年既 soundcard 已經用緊 multibit delta sigma 架喇, 包括 Soomal 自己用來做 review 的 emu 1616m
所以 DSD 標榜 1-bit 根本係搵笨
http://ixbtlabs.com/articles2/multimedia/creative-x-fi.html
The card is equipped with Cirrus Logic CS4398 DAC, advanced multi-bit Delta-Sigma architecture, 120 dB DR and -107 dB THD+N. The same DAC is used in E-MU 1212M/1820M, Creative Audigy4 cards.
Its ADC is the well known top AKM converter, advanced multi-bit architecture, 123 dB DR, THD+N -110 dB.
Many readers are scared by unknown words in the "converter architecture" line. There is an opinion that all high-quality converters (= "parallel", "multibit") are things of the past. Unfortunately, this opinion is supported by many competent and respected experts.
When appeared the first inexpensive converters with oversampling as well as 1-bit delta-sigma modulators, the quality of converters indeed left much to be desired, they were good only for low-end devices. That was their initial destination. However, drawbacks of these solutions were thoroughly analyzed later on. New research was conducted, technologies evolved, new designs were applied. These days modern delta-sigma multibit DACs have little to do with 1-bit delta-sigma modulators 15 years ago. Moreover, all DACs have different circuitry and implementation (quality of the elements). That's what governs the price and quality of a DAC.
Here is an architecture of a typical MULTIBIT DS DAC: 24-bit digital signal is 128x oversampled and then is applied to the digital DS modulator (DSM) operating at 6.144 MHz. In comparison with a 1-bit model, 5-bit DSM of the 3rd order generates insignificant quantization noise in the total noise level. The 5-bit DSM output is converted into a 31-level code and then into DEM, where the problem of nonlinear quantization and temperature dependence is solved. DEM data goes to the analog reconstruction unit, including the DAC on switched capacitors (SC) and the post filter on IIR and FIR filters, increasing the jitter resiliency. |
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發表於 2018-8-28 22:07
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