SACD WINS!

SACD does not have more resolution than 24/96 material or even a CD at 16 bit/44.1k. SACD is a pulse averaging system that is IDENTICAL to a 1 bit Delta Sigma DAC at 64X oversampling (44100Hz * 64 = 2,822,400Hz.) The problem with 1 bit DACs, or SACD, is that they are capable of high resolution but only at low frequencys. A 1 bit sampling system running at 2.8 MHz reaches 24 bit resolution at .175Hz, 16 bit resolution at 43Hz, 12 bit resolution at 1Khz, and 7 bit resolution at 20Khz. As you can see there is decreasing resolution with frequency, in order to have full 16 bit resolution at 20Khz a 1 bit system would need to run at 2.8Ghz, 1000 times faster. In contrast a PCM digital system (like CDs or DVD audio) has full resolution from DC to the nyquist frequency (half the sampling rate). The ONLY advantage that SACD has over conventional PCM digital system is that almost all music now is recorded using a 64X oversampling A/D converter, converted to PCM in a DSP (a lossy step) and when it is played back it is converted to a 1 bit signal once again in a Delta Sigma DAC. SACD simply puts the raw information from the A/D converter on a disk so that there is no conversion loss. DVD audio has a much higher POTENTIAL resolution than SACD but today even CDs are not used to their fullest potential.

Dustin, Sounds like SACD puts up back to the days of 78's and AM radio. In the couple instances where there's both 24/96 and SACD versions of the same master recording, why have the reviewers preferred SACD? Why does everyone prefer SACD over CD. Why is SACD getting almost universal praise? Why does SACD sound great on my system--superior to LPs, CDs, and 24/96? Why does Sony claim that SACD is capable of 100K HZ, while CDs claim 20K, and DVD-Aduio 24K? Your 1 bit explanation is interesting, and I do not understand the engineering, but it seems difficult to believe that SACD has 7 bit resolution at 20K. It would appear to me that at higher frequencies, a detailed resolution would be much more critical.

SACD sounds better than most CDs because the technology used to record in SACD is the same as CDs today. In fact most of the SACD converters that I have seen are based on the same Delta Sigma A/Ds as are used in most PCM converter boxes. They simply grab the stream before the DSP that converts to PCM. So the media on the CD is the same BUT there are more digital conversion steps, Each one of which has some loss. This means that CDs sound worse than SACDs if you use the same equipment to record them. However this is not a problem of the format. There are other ways to "fill the bits" than a Delta Sigma A/D converter but these all cost much more money ($500 a chip or more instead of $5 for a pretty good Delta Sigma A/D). Because these chips are cheap and most people can't hear the difference on their home stereos almost all CDs are mastered on these chips. In fact many CDs are mastered on consumer DAT machines simply using the analog inputs!! (None of which contain very good A/D stages) At least SACDs are mastered on dedicated equipment that is much better designed. I have heard some carefully mastered recordable CDs converted from master tape (just recorded on a laptop computer with a digital in) using a direct conversion A/D converter (these converters directly measure an input signal instead of generating a stream of pulses that are then digital filtered) capable of filling a CDs full resolution and played back on a Direct conversion DAC that sounded almost exactly like the tape. In contrast the commercial master of the same material made on a DAT machine sounded just like any other commercial CD.

P.S. the resolution of a system is easily calculated. For PCM represented with binary numbers you can figure the resolution by raising 2 to the number of bits in a single word. An 8 bit system has 256 possible levels, a 16 bit system has 65,536 possible levels, and a 24 bit system has 16,777,216 possible levels to describe. A 1 bit system like 1 bit Delta Sigma or SACD has only 2 possible levels therefor you must average some pulses to reproduce any given level. If I want a 1 bit system with a resolution the same as an 8 bit system I would need to average 256 pulses, a 16 bit system would need 65,536 pulses to be averaged. (For 8 bit resolution, If I want a "1" I would turn on 1 pulse and turn off the 255, if I wanted a "200" I would turn on 200 pulses and turn off 56, ect...) So to calculate the resolution of a 1 bit system at any frequency just calculate how many pulses it can produce at that frequency.

SACD still has roughly 5 bits of resolution at 100Khz while conventional PCM is limited to the niquist frequency of half its sampling rate, 22.05Khz for a CD. The Nyquist frequency for SACD is also half of its sampling rate, 1.4Mhz.