DSD (Direct Stream Digital)


DSD (Direct Stream Digital) is Sony's proprietary audio sampling technique intended to improve on the Compact Disc. This places DSD squarely in competition with PCM (Pulse Code Modulation) used in DVD-Audio.

DSD takes sampling analogue voltages in a different direction. Where DVD-Audio (using PCM) takes 24bit samples at 96Khz, DSD samples 1bit words at a rate of 2.8442Mhz. The main limitation proponents of DSD believe it has overcome is the need for filters inherent in PCM. DVD-Audio samples using relatively large 24bit pulse codes and filters anything above its specified frequency response of 20Khz. DSD simply takes on the entire frequency range, assigning everything a 1bit code.
Proponents of DSD say DVD-Audio may offer highly detailed sound but filtering with a brick wall set to any frequency can also makes music sound sterile and cold. SACD using DSD is known for a warm sound that is close as a digital source can be to an analogue master recording.

Are there dramatic differences between DSD and PCM? No. The differences are going to be subtle at best and only audible on a high-end system. Don't expect any high-resolution audio format to jump out at you and don't expect to even hear subtle differences between SACD and CD on speakers that aren't priced at about $1,000 per pair.

But if you're really looking to push the limits of high fidelity and want to test the differences between DSD and PCM with your own ears, make sure you have a DVD player capable of decoding true SACD. DSD technology using 1bit words lends itself to easy down-conversion.

Budget Universal DVD players will read SACD information and convert it PCM. Sony conveniently makes many SACD recordings with dual layers so it can be read as either SACD or a CD. There is no extra resolution from SACD being read on a CD player.