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SACD-logoSuper audio cd was a wonderful medium but never made it to the masses. Since economy of scale is imminent for mass media, this successor of the cd failed for what is was set out to be. Sacd might not be dead completely, it’s surely on intensive care. Investing in a new sacd player is advisable only when you own a large collection of sacd’s. Ripping sacd’s has been impossible for a long time due to the perfect copy protection. This has changed recently, although the conditions are rather strict: it can only be done using certain versions of the first edition of the Playstation 3 and only with certain versions of firmware. More details here. Luckily the world wide web offers an alternative. Sacd rips are available through newsgroups and torrents, although in many countries downloading copyright protected material is illegal and fines can be extremely high. In The Netherlands we pay a home copy levy on storage media to compensate for those downloads, meaning that we are allowed to download copyright protected material for private use. Luckily there are also legal DSD downloads, I will list them further on. DSD, or Direct Stream Digital is the sampling method used for sacd. It is a 1 bit system at 64 fold sampling frequency. It works quite simple: a comparator compares the current sample agains the previous and when the current sample is higher in amplitude it generates a 1 and when it is lower it generates a 0. Many a/d-converters in PCM gear work this way after which the 1 bit signal is decimated to a PCM signal in 16 or 24 bits and the accompanying sample rate. In the nineties almost all d/a-converters worked that way too so the signal had to be converted back to a 1 bit signal again. The idea behind sacd was to omit the conversion to and back from PCM and just register the 1 bit signal. If a different d/a-converter was used - especially 2 to 4 bit converters became popular later on - the signal could always be decimated to the needed format. The sample frequency used for DSD is 2.8224 MHz which calculates down to and PCM equivalent of 382,8 kHz at 32 bit floating. The latter format is used in studios when they are unable to process  DSD and is called DXD. In studios DSD and DXD are considered equal in quality and the conversion from one to the other and back is often considered lossless.

PCM versus DSD sampling

 
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