High Definition Audio Formats for Music Listening - SACD (3)
Playback Setup and Content Protection

To make the very best out of SACD music, you need to have the right gear that can deliver the same subtitle detail and dynamic range as supported by this high definition audio format. At the same time, you need to be aware that because of content protection issues, there are some restrictions on interconnectivity. More in this guide.

Connectivity Requirements
for High-Resolution SACD Playback

In order to enjoy the high resolution sound found on Super Audio CD discs, you need a compatible DVD player that can handle SACD discs.

You also need a preamplifier or AV receiver, with either six analogue inputs or an encrypted digital interconnect.

Basically, the situation here is similar to DVD-A requirements in that while DVD-Video audio formats such as Dolby Digital and DTS, can be sent via a player's unprotected digital o/p to a receiver for conversion to analogue form, this is not the case with DVD-A and SACD content.

Like their DVD-A counterpart, SACD compatible players are not permitted to send DSD digital content over an unencrypted digital audio link; if you do, the content protection mechanism will force the SACD player or compatible DVD-player to downgrade to ordinary CD audio quality due to concerns about digital copying.

At present there are two main standard digital connection methods capable of carrying DSD in encrypted form: i.Link and HDMI (version 1.2 or later).

i.Link is generally found on high-end equipment. HDMI is more common in consumer applications, being the standard digital connection method for high-definition video and audio over the same digital interconnect. Still, at the time of this write-up, there are only a few compatible players and A/V receivers capable of carrying raw DSD over their HDMI connection. Instead, some would simply convert DSD to PCM and then carry the PCM encoded signal.

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It should be noted that when working with an encrypted digital interconnect like HDMI with HDCP, all devices in the playback chain will have to be equipped with a valid decryption key, otherwise, it would not be possible to play the high resolution audio. More on HDMI and HDCP can be found under the respective sections of the site.

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Copy Protection

Many have argued that DVD-Audio and SACD are more of an attempt to add copy-protection rather than anything else.  We believe this is not the case, and with the appropriate playback setup, once you hear the high definition multi-channel sound supported by these high resolution audio standards, you will never want to turn back!

SACD employs several copy prevention features at the physical layer, which - up to now - have succeeded in making it impossible to copy SACD content without resorting to the analog hole. It makes use of an active copyright management system (ACMS), a copyright identification system, and both visible and invisible digital watermarking of the audio content itself.

In particular, interesting is the use of physical pit modulation, which is extremely effective against mass illegal copying. It makes use of a new technology called Pit Signal Processing (PSP) in order to modulate the width of the pits on the disc.

This is actually a form of 'Digital Watermarking' that is different in concept to the digital watermarking used in DVD-Audio to prevent copying along the analog path.

The Digital Watermarking technology as used in SACD discs stores the required copyright data as a modulation of the width of the injection molded 'pits' on the disc substrate itself. Hence, copyright data cannot be replicated without the glass mastering equipment used to make the original disc stampers.

Furthermore, the modulation of the pit's width can be synchronized on consecutive turns of the disc in order to form visible patterns on the recorded side of the disc itself in the form of faint text or graphics; hence the name 'Watermarking'.

Beside the visible Watermark on the playing surface of the disc, PSP can also be used to store additional information like the country of origin, mastering house, and other identification codes.

If a disc with no or altered copyright information is inserted in a SACD player, play-back will start for a few seconds, and then the disc is simply ejected from the player. For this purpose, all hybrid players have to be equipped with suitable PSP detection circuitry.

In addition, audio data blocks are also encrypted using an 80-bit encryption algorithm with a key encoded on a special area of the disk that is only readable by a licensed SACD device.

This renders the high definition (HD) layer of an SACD disc unplayable on standard computer CD/DVD drives, or in that case on any non-compatible licensed player, nor can SACD discs be created except by the licensed disc replication facilities.

It is thus clear that SACD seems to have managed to come with an efficient copyright protection system that is most appropriate for use with high-definition audio, since it does not alter the high definition sound in any way. Therefore, the Super Audio CD disc can be used to reproduce the original high definition music in all its subtle detail.

Audio Playback Setup for Super Audio CD

As with all high definition audio, having an SACD player or compatible universal DVD player and an AV receiver, is only part of the game. If you want to get the very best out of your SACD listening, then there is the need for more.

As indicated earlier on in our discussion, SACD supports a much wider dynamic range than CD sound. In other words, if you want to get the very best in music quality when listening to SACD, you need to have the appropriate setup, In particular, if you really want to appreciate this format's potential, a good quality preamplifier/surround sound processor with a signal-to-noise ratio of at least -110dB/-120dB is desirable.

Further more, as with DVD-Audio, if you plan to take your SACD seriously, you will also need to consider investing in five identical full-range speakers. The problem is that from a practical perspective, it is difficult to make use of a floor-standing speaker for the center channel if your audio system also serves as part of your home theater setup. This in view that in a home theater implementation, the center speaker is usually placed horizontally orientated just under or above the TV. This problem would not arise when making use of a front projection setup and an acoustically transparent projection screen, in which case a floor standing center speaker placed centrally just behind the screen would do a nice job for both music listening and movie viewing.

However, more important than the center speaker is having four identical speakers for the left/right front speakers and the left/right surround speakers.

We are not saying that making use of the same audio setup used for a home theater implementation would not suffice; it is just that it is not ideal speaker setup for high resolution multi-channel SACD playback. At the same time, one has to keep in mind that there is also a financial implication to invest in four or five identical full range speakers.

Another issue is speaker placement. As pointed out in our article on speaker placement in the home theater, speaker placement for music listening differs from that for movie viewing. We suggest going through our speaker placement article for the relevant details. If your audio playback setup is intended to serve for both music listening and movie viewing - as is the case with most home entertainment setups, the best approach would be to opt for a flexible speaker mounting solution that would enable you to easily adjust your speaker placement to suit either purpose when needed.

More on SACD Playback Requirements will follow soon.	Last updated on: 4th March 2007
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  ...Part 4: Super Audio CD Music

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