Audio Aero To ‘Improve’ DSD by Converting it to PCM

October 25, in SACD News

Audio Aero’s high-end SACD player takes the unusual step of deliberately converting DSD to PCM in order to improve the standard of playback.

The Prestige A/V player, available in late 2002, is a combination DVD-Video and SACD machine which implements Audio Aero’s S.T.A.R.S.® process, a proprietary 32/192 re-sampling technology. It is used to enhance the playback of DVD-Video, CD, CD-R and CD-RW, and can also be applied to signals routed via the player’s own digital inputs (front left and right channels only).

Uniquely, for SACD playback, the Prestige A/V player uses 24bit 192kHz PCM digital to analogue conversion with what Audio Aero describe as a “DSD/PCM bridge”.

Intrigued by this, I asked Jean-Paul Combelles, technical and commercial manager for Audio Aero just what is meant by “DSD/PCM bridge”?

The DSD to PCM bridge is a DSD to PCM converter that affords a 9dB improvement to the SACD signal-to-noise ratio by reducing the high frequency noise present due to the 2.82MHz sampling frequency. This will also allow enhanced functionality from the analogue stages,” explained Jean-Paul.

This statement actually confirms what many DSD sceptics have been citing as a negative aspect of SACD for some time, so I wanted to clarify just what Jean-Paul meant. I asked him to confirm that all DSD (SACD) sources are converted to PCM in the player, where a filter removes some of the ultrasonic noise present and thereby improves the signal-to-noise ratio by 9dB. I also asked that if this really were the case, whether he thought that SACD proponents would object to DSD being converted to PCM prior to D/A conversion? A pure DSD signal path appears to be the panacea of many SACD listeners.

Jean-Paul reiterated his earlier response: “…suppressing the ultrasonic noise will allow better functioning of the following stages (DAC and analogue stage). By reducing this noise, the residual signal we create will be boosted by 9dB using our enhancement techniques.” Unfortunately any more technical detail is considered confidential.

We do know however, that the DSD to PCM conversion takes place within the S.T.A.R.S. 2 circuitry, which was exclusively developped for Audio Aero by Anagram Technologies.

My follow-up questions touched on the subjects of bass management and time alignment, both of which are important to the role of any SACD player. Bass management is another thorny issue as most people believe the filters within SACD players operate by converting the DSD data to PCM, although at the recent AES convention directors of the SACD Project explained to HFR reporters that this is untrue, SACD bass management actually takes place within the DSD domain.

That in turn begs the question why folks believe the performance of their SACD player suffers when bass management is engaged, a view also shared by Audio Aero, although they don’t blame PCM. In fact, Jean-Paul objects to all bass management, which is why the Prestige A/V player doesn’t have any…

There is no bass management (as it would corrupt the signal). We will not use current elliptic filters as it would create some distortion in the output signal. We prefer to keep the whole bandwidth intact; building a high end product, you can expect the speaker system also to be high end. So, all the speakers should be able to handle the complete signal with all its dynamics.” An idealistic view certainly, but one that matches the Audio Aero philosophy.

Time alignment is critically important to any multi-channel system, but unfortunately the Audio Aero doesn’t offer any. “There is no time alignment for SACD, except to compensate the delay due to the re-sampling induced by the S.T.A.R.S. processor,” explained Jean-Paul. “This is managed in the digital domain. We don’t manage time delay ourselves as it’s already made in our OEM SACD/DVD base.

Additional prominent features of the Prestige A/V player include a tube (valve) output stage for the two main channels with it’s own volume control and integral DTS, Dolby Digital and DSD decoders.

The philosophy of the player is the same as that for the Capitole, one machine with lots of features and only the amp to connect (and the video for the Prestige). We want to minimise the number of interconnects and, at the same time, improve the sound by reducing connections. So, except for the separate power supply, everything is integrated into the player.

Progressive scan is standard and will be available with a 12-bit output; a 14-bit video DAC is an upgrade option. Both NTSC and PAL progressive scan are supported.

Audio Aero, founded in 1997, is the high-end audio division of the Mazиres Aviation Group, the company is based in Toulouse (south-west of France), the ‘silicon valley’ of French aeronautics, located near the Airbus office and Aйrospatiale plant. The group incorporates five high-tech companies with interests in aeronautics, racing and audio, the French equivalent of TAG McLaren?

More preliminary information:

  • Supported formats: SACD (two- and six-channel), DVD-Video (sample rates up to 24-bit 96kHz), CD, CD-R, CD-RW and CD-Video
  • Separate power supply (switching pre-regulation PSU for digital)
  • Exclusive S.T.A.R.S. 2® 32-bit 192kHz Re-Sampler with DSD to PCM conversion (to improve SACD performance) with sub-miniature tube output stage (for SACD, DVD-Video, CD, CD-R, CD-RW and all digital inputs for right and left channel only)
  • DTS and Dolby Digital 5.1 decoders
  • 1 Ч DAC 24-bit 192-kHz Multibit Delta/Sigma for front left and right channels
  • 2 Ч DACs 24-bit 192kHz for the surround channels
  • Built-in volume control (six-channel selectable + master control)
  • Progressive scan with 12-bit DACs (optional 14-bit DACs)
  • Integrated switching between sub and height channel configuration
  • Digital inputs: BNC, RCA, AT&T, Toslink and AES/EBU (upgradable to PCM 24-bit 192kHz inputs/outputs)
  • Digital output formats: MPEG2, DTS, Dolby Digital and PCM
  • Analogue outputs: Balanced (with professional line driver) and unbalanced for the six-channel array
  • Analog inputs: One balanced (with professional line receiver) and two unbalanced
  • Video outputs: S-Video, CVBS, YCbCr/YPbPr and RGB/RGB progressive

Audio Aero Prestige A/V DVD-Video and SACD playerAudio Aero Prestige A/V DVD-Video and SACD player

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