AndyC_772;198601 Wrote: > 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.
Ok, thanks Andy, I think we are closer to the same page now. I figured it wouldn't hurt to play with. I'm also not sure how my processor handles 16 vs 24 bit and may do some odd things to be backward compatible with different devices. So I figured it wouldn't hurt to play with. The first thing my processor does is shift the data down to make headroom for some processing and calibration. I don't know if it does that in 16bit on 16bit data or converts first. It is capabable of outputing 16bit data to older active speakers and that data is just lost. With newer active speakers I can't tell what it does because SPDIF data is encrypted. So far I hear no difference. But I need to try it on a wider range of music. Also just a thought wouldn't replay gain (done digitally) or any normalization now have lot headroom in 24bit? -- mswlogo ------------------------------------------------------------------------ mswlogo's Profile: http://forums.slimdevices.com/member.php?userid=9090 View this thread: http://forums.slimdevices.com/showthread.php?t=34892 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/lists/listinfo/audiophiles
