mswlogo;198595 Wrote: > But didn't you just say 16 vs 24 wouldn't make any difference in the > actual jitter of the 32bit word. Why would it matter which bits are > being used in the test? > > So your saying each bit has it's own jitter measurement? > > Or if he toggled Bit 8 of the 24bit word he'd get the same measurement > as bit 0 of 16bit? > > That makes no sense to me.
I must admit, I don't know for sure why the test results are different - but I suspect it's much more to do with flaws in the test itself than the behaviour of the Transporter. For example, the AK4396 DAC is a 128x oversampling delta-sigma device, so there will always be data-dependent noise at frequencies outside the audio band. More than likely there is an analogue filter between the DAC and the output socket to attenuate this noise. Now suppose that, in order to allow excellent flatness up t0 22kHz, this filter has a cutoff around 100kHz. The test equipment is now trying to pick out jitter in the order of 100ps (which is the period of a clock running at 10GHz) in a signal which has been filtered to remove everything above 100kHz. Is that a sensible thing to try and do with any degree of accuracy? Or is the measurement likely to be influenced by the audio signal? I strongly suspect the latter. I'd bet that if the jitter measurement were made at the MCLK pin of the AK4396 - the correct place to measure it - that it would be completely independent of the data. -- AndyC_772 ------------------------------------------------------------------------ AndyC_772's Profile: http://forums.slimdevices.com/member.php?userid=10472 View this thread: http://forums.slimdevices.com/showthread.php?t=34892 _______________________________________________ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/audiophiles
