audioengr;147353 Wrote: > > cliveb;146937 Wrote: > > Unfortunately, the article by Steve Nugent that you cite is utter > > hogwash. His thesis regarding the superiority of computer based > > playback over CD is founded on the completely erroneous axiom that the > > master clock in a CD player is in the transport. It isn't.> > > > Hogwash eh? > > How many DAC's and transports have you actually opened-up? > > If you had done this as I have, you would have found that ALL > Transports have a master clock that is both a PLL and part of a > spindle speed control system. This is why I have installed > Superclocks in 100's of customers Transports in order to reduce the > S/PDIF signal output jitter. Of course the clock is part of the spindle control system. That's the point: the clock determines the spindle speed, not the other way round.
The fact that you've modified hundreds of CD players with different clocks doesn't make any difference to the fact that your article is misleading in the extreme. You say that there are a number of sources of jitter, and include in that list the pits on the CD itself and the reading of those pits by the laser. Nowhere in your article can I find any mention of the fact that these jitter sources are completely irrelevant, since the data that comes off the CD is buffered and then clocked out by the master clock. The point is that in any digital source, the samples are fed into a buffer and then sent to the DAC (or SPDIF output) under the control of a free-running clock. The buffer DECOUPLES the DAC (or SPDIF transmitter) from the vagaries of the process which supplies the data. On the source side of the buffer, it doesn't matter whether the data is supplied by reading a spinning optical disc with a laser, receiving a network data stream (at the other end of which is a spinning hard disk read by magnetic heads, of course), or a talented morse-code operator with very fast fingers. Your article is clearly worded such that the reader will infer that the jitter in the CD's pits and resulting from reading them with the laser are transmitted through to the DAC (or SPDIF transmitter). This is simply not true. The fact that Empirical Audio is the vendor of a CD copying device that purports to reduce these sources of jitter, and therefore has something to gain from spreading such misinformation, makes me a little suspicious as to your motives. I may have muddied the water a little when I said the the master clock is not in the transport. In this context (a single box CD player), by "transport" I am referring to the opto/mechanical disc reading system. It occurs to me that many people understand the word "transport" to refer to a device which emits an SPDIF signal to an external DAC. In that context, then yes, the master clock is in the "transport", but it's still on the DAC side of the buffer. audioengr;147353 Wrote: > It is also the reason why rewriting a CD with a low-jitter writer such > as a Reality-Check makes such an improvement in the Transport output > jitter. The pits are more accurately located and easier for the > Transport to read, and therefore the PLL and master clock are less > effected due to less jitter as the pits are being read. The hypothesis that making CDs easier to read has an effect on the jitter of the master clock has been shown to be unfounded in the Prism/DCA paper referenced earlier in this thread. -- cliveb Performers -> dozens of mixers and effects -> clipped/hypercompressed mastering -> you think a few extra ps of jitter matters? ------------------------------------------------------------------------ cliveb's Profile: http://forums.slimdevices.com/member.php?userid=348 View this thread: http://forums.slimdevices.com/showthread.php?t=28621 _______________________________________________ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
