I found the following statement on "rec.audio.high-end" It was posted 12/16/2003 by a Phillips engineer. For informational purposes only> WVK "SACD is indeed fundamentally flawed. Using 1-bit as a conversion method can be a valid choice when the analog circuit does not have performance higher than the 1-bit signal. To use this as a data format, thus binding everyone to the noise and distortion limits, is quite another thing... SACD is a typically Japannish invention in that it is a solution to a nonexistent problem (decimation-interpolation), which in turn creates some very real problems left for real engineers to solve. Some examples: 1. Splicing (editing) two DSD signals together creates a "click", even if both represent silence. 2. Any processing (except delay results in a longer word length. Getting back to 1-bit requires another stage of deltasigma modulation. Sony dreamt of a new signal processing paradigm operating entirely in DSD. It was not to be - they even officially admit it now. Any quantisation mixes the signal with quantisation noise. They can no longer be separated. This is not much of a problem at 24 bits. At 1 bit however... well... 3. The accumulated noise from previous conversions reduces the deltasigma modulator's headroom. After 5 conversions (e.g. level control, eq, mixing, fader etc), the modulator already overloads at silence. 4. DSD is not distortion-free. 5. The signal bandwidth and the noise zone overlap. In a correctly designed converter, the signal occupies the "clean zone" only, thus allowing the noise to be filtered away. With DSD, the noise zone starts at 20kHz but the signal bandwidth extends -by Sony's definition- to 100kHz. The SNR over 100kHz is only 30dB. Many amplifiers produce audible distortions when presented with this noise (hence the switchable filter on many SACDs). It was "invented" when someone took a CS5390 chip, wired the 1-bit test outputs straight to a D/A converter and liked what he heard. Thus, the standard was fixed at 1-bit/64fs which happened to be the internal operating parameters of this particular chip. This chip is now long obsolete. Current ADCs operate at rates of 128fs and over, at 4 bits or more.