has anyone tried PS Audio perfect wave duo

AL,

Yes, it would make little sense to output time sensitive data directly from an optical read device. I've always assumed that most or all devices do not do this but was not sure.

Usually if a cache is not big enough, a clear audible dropout will occur I believe and not a subtle change in sound.

I would expect the same to occur but much more frequently if bits were read direct from a relatively slow and more error prone optical device and that seldom seems to occur with most properly operating readers.

Does that sound right?

Hi Mapman,

Yes, if the cache were not large enough to support the timing variations of the read mechanism, clear audible dropouts would occur.

If the optically-read data were conveyed to a dac, or to the internal dac of a cdp (transport plus dac in one unit) without any memory cache in between, I would expect the result to be a total mess combining dropouts with various distortions associated with the timing variations.

Best regards,
-- Al

Al and Mapman,

What the Perfect Wave Disc player does is read data off the disk like a computer - not a CD player. That is, will re-read sectors if there is an error until it gets it right rather than a one-pass stream that a CD player does. It essentially achieves the benefit of a file based transport with a disc based one and assures that the data is always perfect. Also, it can do pretty much any format including file based formats on DVD (which is how many of the new high res formats are being distributed).

Combined, the main benefit of the two pieces is all about avoiding the hallmark problem areas of typical disc players and DACs. By "ripping" the data like a computer, the disc player gets the data correct to begin with. By keeping it in I2S format all the way to the DAC chip, it keeps it perfect. No error correction, no jitter, no re-clocking of digital stream data, no latency problems. Basically, what we have been spending thousands on for Pace Cars and re-clocker mods and such is no longer necessary.

Everything I've seen and heard thus far tells me it's pretty much the best "technology" out there. The real question I think is whether you like the sonic quality of the DAC or not. It would be nice if a standardized I2S interface could emerge for transport devices and DACs so we can replace the error prone SPDif, Toslink, and USB ones. The clever use of the HDMI hardware might just be the ticket.

Shazam,

I was under the impression that most optical drives, audio or computer, do rereads of data normally when errors are detected? I didn't think most modern CD players were one pass only because frankly there would seem to be no reason for them to suffer with that limitation.

Thanks for the good explanations, Shazam. You should replace whoever writes their literature!

I do agree that the file-based read, and the I2S interface (which avoids multiplexing the data and clocks together) sound like excellent approaches. Hopefully, as you say, the I2S approach, or something similar, will be adopted by others.

What I was taking exception to as misleading, though, is exemplified by this paragraph at their site, in the description of the transport:

In a standard CD player or Transport, the master clock is synchronized to the optical disc reading mechanism. This means you are basically relying on a mechanical spinning mechanism and all of its correction systems to give you a perfectly stable, fixed clock to feed the DAC. It does not work and it is not stable.

Here's the problem. Optical disc readers are constantly changing the rate at which the data is coming from the disc. Sometimes it comes faster and sometimes it comes slower than the fixed speed of an asynchronous clock. If that data is coming in faster than the clock, you get a traffic pileup and the system crashes. Too slow and nothing comes out.

The Digital Lens has a large and smart memory storage buffer. It's big enough to handle any speed variation of the optical disc reader.

That would appear to indicate that in other transports and players the timing of data to the dac is subject to fluctuation identical to the fluctuating timing of the data coming off of the disk. It was sufficiently misleading, in fact, to have apparently misled one of our most intelligent and experienced members, with whom I was having the discussion above. :)

Best regards,
-- Al