DVD Player Reviews
Dear Gary: Your Ultimate Widescreen Review DVD Movie Guide has reviews for many current DVD players. Comments about audio quality from the digital out ports of several of these players make no sense to me. The reviewers claim that audio quality USING THE DIGITAL OUTPUTS varies greatly among the players. How is this possible? For example, the DTS digital soundtrack on a particular DVD represents a unique stream of digital bits, which are sent down the optical (or coaxial) digital cable to the DTS processor in my AV receiver. My receiver should get the same bits from any properly-working DVD player. Why should it matter which DVD player I am using, so long as no bit errors are introduced? Even jitter arguments don’t explain it. Good DAC chipsets (as any good AV receiver should have) smooth out reasonable jitter so that it does not affect the D-A conversion process at all. And all of this happens in my AV receiver, NOT in the DVD player. So again, why should it matter which player I am using? I would like to have confidence that the people who contribute to your magazine know what they are talking about. If there is something I am not understanding here, what is it?
Dr. Paul Finlayson, Navigation and Mission Design, Section 312 Jet Propulsion Laboratory, pafinlay@mail1.jpl.nasa.gov
Audio Review Editor Richard Hardesty Comments:
Most of the digital data that your computer uses is not time sensitive. Get the bits right and everything is hunky-dory. A digital bit stream made up of discrete samples that represent the amplitude of an analog signal at a series of very specific points in time is quite different. This data stream is extremely sensitive to timing. You can have all the correct bits in the digital domain and still deliver an analog signal that is grossly distorted due to timing errors. The cause of timing errors can be electronic or mechanical. You can read about various timing error phenomena on the dCS Ltd. Web site at: www.dcsltd.co.uk/papers.htm and reams of literature on this and related subjects are available elsewhere. There is no mechanism in the DACs in your receiver that can correct for many of these timing-induced errors. There are many other potential causes for audible differences between optical digital transports such as read errors caused by vibration, etc. but regardless of the reasons, the simple facts are that properly functioning DVD players sound different, even through the digital outputs. Widescreen Review writers have had the opportunity to listen to a wide variety of optical disc players through high resolution audio systems and we have observed that there are substantial audible differences between various models. In the subjective portions of our product reviews, we report on what we hear. Subjective opinions are just that. These opinions represent our listening impressions and are based on substantial experience with a vast array of components but are not substantiated by objective data. Readers who believe that bits are bits should buy the cheapest players they can find. Readers who have come to trust our opinions can use them for what they're worth. Readers who want to hear differences for themselves should take a mass market DVD player to a high-end dealer who sells California Audio Labs or Theta or some other high quality brand and compare the sound of the mass-market player to a high-quality player.
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