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Memory Players

Hi Folks.

Well, the upgrade itch has got me and it may be time to once again dip my toe into the technology pool. It's actually been a while since the last "itch", so I'm O.K. with it.

I am still using a Denon DVD500 as my digital reference source. This unit was a giant killer in it's day with it's heavily constructed chassis, extensive shielding, and those wonderful Burr Brown 1704 24/96 dacs.

Unfortunately, CD quality has worsened. The discs seem thinner, the discs sometime vibrate, then vibrating the dacs, blah, blah, blah.

Who has experience with either the Nova or PS Audio Memory Players (or others like it) and what could you tell me?

I extracted the information below from what I believe to be the old Nova website. It's very interesting.

"“Read-until-Right” is the principle that lies at the heart of the Nova Physics Group Memory Player and that enables it to achieve its stunning sonic effects. When a CD is placed in the Memory Player, the laser will first read the disc like any other CD player, but what distinguishes the Memory Player is what happens when the laser encounters a hard to read spot on the disc (and this happens hundreds or even thousands of times per disc, either from dirt, scratches, surface imperfections or eccentricity). A standard CD player at this point will introduce Error Code Correction or Error Concealment Correction (ECC) and Parity Bits. The Memory Player disables ECC and Parity Bits and engages its Read-Until-Right (RUR) and Dynamic Laser Positioning (DLP) software. RUR attempts to retrieve the original information on the disc by engaging its DLP that repeatedly shifts the laser angle. Only when the information can’t be extracted after hundreds of attempts do Error Code Correction and Parity Bits kick in, creating as perfect a theoretical facsimile of the missing information as possible, as in standard CD players."
128x128buscis2

Showing 3 responses by almarg

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almarg
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Does the MP utilize a ROM drive. If so, I was actually unaware of ROM drives incorporating error correction.
I believe that all or nearly all CD-ROM and DVD-ROM drives will not perform error CONCEALMENT (i.e., interpolation), but I'm pretty certain that they do perform bit-perfect error CORRECTION when reading an audio CD (to the extent that it is possible to do so for the errors that occur), utilizing the error correcting codes that are on the CD. I'm not 100% certain, but I presume they do that to the same extent that a standalone player or transport would.

BTW, although the CIRC error correcting codes that are used on audio CD's are extremely powerful, as indicated in the thread I linked to in my previous post, those used for data CD's (as opposed to music CD's) are even more so, as might be expected.

Following is an excerpt from this old (1988!) writeup on CD-ROM drives:
This first level error correction (the only type used for CD Audio data) is extremely powerful. The CD specification allows for discs to have up to 220 raw errors per second. Every one of these errors is (almost always) perfectly corrected by the CIRC scheme for a net error rate of zero. For example, our tests using Apple's CD-ROM drive (which also plays audio) show that raw error rates are around 50-100 per second these days. Of course, these are perfectly corrected, meaning that the original data is perfectly recovered. We have tested flawed discs with raw rates up to 300 per second. Net errors on all of these discs? Zero! I would expect a typical audio CD player to perform similarly. Thus I expect this raw error rate to have no audible consequences.

So why did I say "almost always" corrected above? Because a sufficiently bad flaw may produce uncorrectable errors. These very unusual errors are "concealed" by the player rather than corrected. Note that this concealment is likely to be less noticeable than even a single scratch on an LP. Such a flaw might be a really opaque finger smudge; CDs do merit careful handling. On the two (and only two) occasions I have found these, I simply sprayed on a little Windex glass cleaner and wiped it off using radial strokes. This restored the CDs to zero net errors.
Regards,
-- Al
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almarg
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Thanks very much, Ed (Buscis2).

Here is an excellent paper from Linn, which is essentially consistent with what I had said about CD-ROM drives, but provides some good elaboration.

Best regards,
-- Al
almarg's avatar
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almarg
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The statement about the Nova player that is quoted in the OP is misleading. What occurs "hundreds or even thousands of times per disk," which in conventional players and transports is subjected to what it refers to as "Error Code Correction," results, at least in reasonably contemporary implementations, in bit-perfect recreation of the original data on the CD. What it refers to as "Error Concealment Correction," which results in less than bit-perfect recreation of the original data, only comes into play rarely (not at all on many CD's), in extreme situations such as severe scratches, or disks that are otherwise in poor condition.

See my post here, and the Wikipedia links provided in my previous post in that thread. Also see two posts in that thread in which Steve provides added confirmation, one of them stating that "with a clean CD, there are virtually no read errors with modern read heads. There will be some differences in jitter with each play however, based on lots of things, such as AC power, ground loops in the system etc."

The quoted statement about the Nova player appears to indicate that it disables BOTH error correction and error concealment until such time as its RUR process has been unsuccessful. If true, that would say essentially that their approach creates a problem which it then solves.

Regards,
-- Al
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