The first SACD players, and the first SACD recordings, were 2-channel only. But SACD was always capable of supporting high-resolution multichannel audio. Now that multichannel discs and players are available, it's important to clarify the distinction between the two different types of operation, and explain the various ways in which audiophiles may set up and use the format.

Two-Channel SACD Material Playback
Mode 1: A 2-channel system with a 2-channel preamplifier or integrated amp. No restrictions. If the player lacks bass management for SACD material, the left and right speakers can be used full-range or with the highpass/lowpass filters built into most powered subwoofers.

Mode 2: A multichannel system with an A/V receiver or surround processor using all digital processing. That is, the surround processor or receiver has no analog bypass in any mode; rather, any analog signal present at one of the L/R analog inputs is immediately converted to digital using the processor's internal analog-to-digital (A/D) converters. All internal processing is then performed in the digital domain and the signal is reconverted to analog at the output of the processor or receiver, using the surround processor or receiver's digital-to-analog (D/A) converters.

This system will play back 2-channel SACD material from its L/R analog inputs. But because of the extra A/D and D/A conversion steps, the playback resolution will depend not only on the quality of the converters, but will be limited as well by their sampling rate and bit depth. The sound may still be very good, but it will no longer be true SACD. It is likely that something will be lost in the conversion process. In the worst case, the sound could well be marginally inferior to CD. The bass management of the surround processor or receiver will be fully functional. Multichannel SACDs cannot be played back through this system except in 2-channel form.

Mode 3: A multichannel system using an A/V receiver or surround processor with 2-channel (L/R) analog inputs. Sources connected to those inputs are processed entirely in the analog domain and are never converted to digital as they pass from input to output. For SACD, this situation is identical to that in Mode 1, above. The sound will pass through the electronics limited only by the quality of the processor or receiver's analog circuits. If analog bass management is provided, that, too, will be fully functional. But the system will not play back multichannel SACDs except in 2-channel form.

Multichannel SACD Material Playback
A multichannel system using an A/V receiver or surround processor having a full 6-channel (five main plus subwoofer) analog bypass input. This system will play back either 2-channel or multichannel SACDs within the quality limitations of the surround processor or receiver's analog circuits. In general, these processors and receivers do not provide bass management for the multichannel analog bypass input. This means you must either use five full-range speakers for SACD playback, employ a separate subwoofer for each channel, ensure that the SACD player itself provides bass management compatible with your system, or use an outboard bass management box.—Thomas J. Norton