Chapter 3 of Analog Device's "Data Conversion Handbook" (by Walt Kester) discusses this:
Kester Wrote: > > The basic concept of an oversampling/interpolating DAC is shown in > Figure 3.30. The Nbits > of input data are received at a rate of fs. The digital interpolation > filter is clocked at > an oversampling frequency of Kfs, and inserts the extra data points. > The effects on the > output frequency spectrum are shown in Figure 3.30. In the Nyquist case > (A), the > requirements on the analog anti-imaging filter can be quite severe. By > oversampling and > interpolating, the requirements on the filter are greatly relaxed as > shown in (B). Also, > since the quantization noise is spread over a wider region with respect > to the original > signal bandwidth, an improvement in the signal-to-noise ratio is also > achieved. By > doubling the original sampling rate (K = 2), an improvement of 3 dB is > obtained, and by > making K = 4, an improvement of 6 dB is obtained. Early CD players took > advantage of > this, and generally carried the arithmetic in the digital filter to > more than N-bits. Today, > most DACs in CD players are sigma-delta types. > The take-home message is that you want to separate the "images" or artifacts from the Nyquist-limited bandwidth. That way, you're anti-imaging filter doesn't mess with the real data (as much). I have a hardcopy version of this book, but it is also available online (for free) as a series of "lecture" notes in PDF format. Very good reading if you're interested in how modern (and ancient) DACs really work. -- ezkcdude SB3->Derek Shek TDA1543/CS8412 NOS DAC->MIT Terminator 2 interconnects->Endler Audio 24-step Attenuators (RCA-direct)->Parasound Halo A23 125W/ch amplifier->Speltz anti-cables->DIY 2-ways + Dayton Titanic 10" subwoofer He's not hi-fi, he's my stereo. ------------------------------------------------------------------------ ezkcdude's Profile: http://forums.slimdevices.com/member.php?userid=2545 View this thread: http://forums.slimdevices.com/showthread.php?t=26685 _______________________________________________ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
