Triode Wrote: > So perhaps there is potential to futher improve with expensive after > market clocks, but we are already getting low jitter in comparison to > lots of digital gear.
That's an understatement:) In the >10Gb/s equipment we build, we use (for meeting SONET requirements), very high accuracy, very low jitter oscillators, and then apply digital jitter attenuation techniques; the components for which easily exceed the (probable) COGS of a Squeezebox2. The result is a reference clock with jitter at sub-6ps rms. That also is with excruciating detail paid to layout of the board and routing. Sean, if your jitter distributions are not Gaussian, i.e. if there is enough deterministic jitter (from power supplies, for example) present, it makes sense that you could see the same sigma but different pk-pk values. This is consistent with making changes to the power supply, since one would expect that you would be changing the Dj component of the the jitter. If the jitter is not Gaussian, the sigma value is not very useful. The first jpeg in the links you posted definitely looks to have a "leftward" skew. Actually both of them do. Also, of course, you would have to have the same number of samples in each measurement to see the same pk-pk values, since random jitter is unbounded. You probably know all this, but here's a link for others reading the thread: http://www.mtron.com/pdf/contentmgmt/oscillator_jitter_basics-2.pdf Additionally, I have seen large (percentage-wise) differences in jitter given by different instruments, when pushing the limits of those instruments (comparing results from Agilent and Tek scopes, for example). Rj/Dj separation results are always different since the companies use different techniques for calculating the numbers. Finally, you are to be commended for achieving such a low rms jitter in a low-cost box like this. The numbers you measured are extremely low! -- Dave D _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/lists/listinfo/audiophiles
