After four years in the wilderness, Sony is back with an incredible new flagship CD/SACD player, the SCDXA5400ES.

It bristles with technology, much of which is new, or new at least, to Sony. At first glance, it's a dead ringer for Sony's previous SACD player, the SCD-XA9000ES. From the front they look practically identical, although the control functions have been shuffled around.

The display is broadly similar, however, and the loading drawer and physical construction are closely related. The new model shares the 9000's superbly engineered smooth-running drawer mechanism, a headphone volume control and Sony's usual ratcheted track change rotary control that makes day to day operation so quick and so responsive. Viewed from the back the difference is more obvious.

The biggest obvious difference from the 9000 is that the new model is stereo-only in its baseline standard trim. The ability to run a multichannel set-up has been retained, but is only accessible via HDMI.

This typically means using an HDMI-equipped multichannel amplifier such as the new Sony STR-DA2400ES, which has four HDMI inputs (a sample of which was supplied by Sony for this test).

This is also a moderately affordable AV receiver and, for that reason, a less than optimal choice than the more high-end SCDXA5400 in this application. More on this a bit later, which will also include something on what Sony's HDMI has to do with HATS (High-quality digital Audio Transfer System) . In the meantime, optical and coaxial outputs have been retained, but only for CD.

Improved sonic purity

This is not the first Sony SACD player to boast a digital output, but the optical and coaxial output on previous models, including the 9000, were limited to 16-bit CD resolution and Sony's iLink did not deal directly with DSD, but a PCM (and inevitably degraded) representation of it. DSD is the native file format of SACD, though some SACD's take their DSD from PCM files.

This is also the first Sony player with an uncompressed digital output from DSD and the first Sony player to include HATS technology on its HDMI output.

One of the claimed benefits in this application is that the HDMI interface doesn't mutilate the signal in pass-through mode, so the number of D/A and A/D conversions is reduced, the simpler circuit path translating into upgraded sound quality.

Sony talk of enhancements to sonic purity and staging, better focus and atmosphere and improved bass and power.

HATS technology

HATS addresses the problems of simultaneously communicating six channels of digital data at 2.8224MHz, which would otherwise result in timing (jitter) errors.

HATS uses an algorithm that rejoices under the title of 'command-based rate control of isochronous data flow' and includes variable speed transmission from the player and a buffer memory in the receiver, an arrangement mediated by a command signal which controls transmission speed, so that jitter performance defaults to the inherent accuracy of the receiver and player master clocks.

No separate clock connection is required and HATS is unresponsive to the marginally different clock rates you can expect to find in the player and the receiver, which are typically a few tens of ppm (parts per million). An earlier version of HATS was available on the 9000, but using iLink rather than HDMI.

Even with HATS, the HDMI output is still compatible with the HDMI inputs on other equipment. But full-on DSD with HATS requires a compatible receiver/decoder, such as is fitted to the Sony STR-DA5400ES. The lower-end Sony STR-DA2400 decimates DSD to linear PCM which, if Sony's word is to be taken as read, must be at the cost of ultimate fidelity.