Због чега се и даље дискутује о различитим приступима читању дигиталног сигнала на ЦД медију?
Због чега се озбиљни произвођачи опреме за репродукцију враћају основном стандарду уписа дигиталног сигнала од 16 бита и фреквенцијом од 44,1 кХц? И због чега избацују дигиталне филтере код процеса обраде сигнала?
Погледајте чланак у наставку. Више о овоме на вебсајту http://www.sakurasystems.com/articles/Kusunoki.html
Non-oversampling Digital filter-less DAC Concept
by Ryohei Kusunoki
|To Confirm the Original 44.1kHz/16bit Format
It is exciting to create something new. Some people just grab a soldering iron, others deliberately start a simulation. Everyone seems to have his/her own approach. In my case, it starts with going back to the basics, research the history, and re-construct the whole picture in my mind. On starting this project I did research as many resources as I could put my hands on.
As the new generation of CD format is appearing on the horizon, I thought the basic concept should be „To Confirm the Original 44.1kHz/16bit Format“. A CD in our hands has exactly the same data, every bit to bit, as to the one that left the studio. To recall this dreamy fact, the above theme would be quite appropriate. Any high-bit or high-sampling does not have its raison d’être unless it surpasses this level of accuracy.
All of the above is based on the basic sampling rate. When in 8 x oversampling and 20bit, that number would be 1.35ps (diagram 2). This is a totally impossible number to achieve for a separate type DAC which has to recover the clock by PLL. This means that under an average jitter environment, the oversampling can not operate theoretically, and lowers the accuracy within the operating field. In short, just by oversampling the original data, 16bit accuracy can not be satisfied anymore.
2) Oversampling and High-Bit
For example, in case of a high-performance digital filter SM5842, this processing is done in 32bit and the filter round them up to 20bit to the output, creating more errors in the re-quantizing process. Recently, this problem was dealt with and a filter was created which can produce 8 x sampling all at once. But even with that, as long as you can’t output the internal word length as it is, there’s no way you can prevent the errors to occur.