CDs are often claimed to perfectly reproduce music. But in an editorial on August 22 about the dangers of "Digitalized History," the New York Times asserted "even in the best digital recordings of live performances, there is a loss of grain, of substance."

Is the Times correct?

Answer: Yes, the New York Times is correct in the case of all digital sound, including CDS, DVDs, DVD-Audio, Theatrical movies which use digital equalizers, digital tape decks, TV and MP3s, which use Pulse Code Modulation (PCM). In recording sound, the PCM operating system uses a brick-wall filter to cut out all information above 20 kHz. This truncation has two deleterious effects on music: First, it destroys the harmonics by removing the information above 20 kHz, which, though inaudible to the human ear, provide part of the chain reaction that give music its sound. Second, the filter itself, in vibrating introducing some spurious information in the audible range. The remaining information, after being converted to a digital bit stream, is then "quanticized" into 16-bit words. Such quanticization requires further filtering and rounding off. If there are even minute fluctuations in the current, it results in conversion errors. On playback, the PCM process is reversed, but the missing information --including information above 20khz— can not be restored, no matter how sophisticated (or expensive) the digital to analog electronics. It is not "lossless" compression. In a PCM replication, a truncated part must stand for the whole music. The only exception in digital sound is SuperAudio (SACD), which uses a different operating system, called Direct stream Digital. Direct stream Digital, unlike PCM, does not chop out the bandwidth above 20 kHz or filter the digit information into multi-bit words. Even this exception applies only if there is no PCM equipment, such as digital equalizers, used in the recording and playback process.

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