Digital Disc Formats - CD, HDCD and SACD
For over the 30 years the CD and its variants have served as the primary physical digital audio format for consumers.
CD 'Compact Disc' - Developed by Philips and Sony the compact disc was the first consumer digital audio disc format, initially released in 1982. The CD digitally encodes audio using 'PCM' (Pulse Code Modulation) storing 74-80 minutes of two-channel 16-bit PCM encoding at a 44.1kHz sampling rate per channel, giving a dynamic range of 96dB and covering the 20Hz-20kHz audible range.
HDCD 'High Definition Compatible Disc' - Developed by Pacific Microsonics and now owned by Microsoft. HDCD offers an increased dynamic range, encoding the equivalent of 20 bits worth of data in a 16-bit digital audio signal via a series of custom processes. A HDCD capable player is required to take advantage of this increased range, however HDCD's are compatible with standard CD players. When played in a standard CD player the HDCD will reproduce the same output as a standard CD.
SACD 'Super Audio CD' - Once again Philips and Sony collaborated to develop the SACD, aiming to supersede the standard CD. The density of information for SACD is similar to that of DVD, capable of storing 4.7GB of data or 110 minutes of stereo audio or up to 6 channels for surround sound.
SACD audio encoding is 1-bit DSD (Direct Stream Digital) which gives more accurate sound reproduction than 16-bit PCM, the sampling rate of 2.8224 MHz, delivering a dynamic range of 120dB from 20 Hz to 20 kHz and an extended frequency response capable of up to 100 kHz.
Please note there are 3 types of SACD:
'Hybrid' - featuring the 4.7 GB DSD layer (HD layer) for SACD playback as well as a PCM layer, enabling the disc to play as a standard CD in a non-SACD player.
'Single-Layer' - DVD-5 encoded with one 4.7 GB DSD layer, suitable for SACD compatible players only
'Dual Layer' - DVD-9 encoded with two DSD layers, totaling 8.5 GB, and no PCM layer. Dual-layer SACDs can store nearly twice as much data as a single-layer SACD. Suitable for SACD compatible players only.