Archimago wrote: > Just thought this spectral frequency plot looked interesting for the > PonoPlayer! > > Lots of high-frequency gets through of course but not the usual Nyquist > ringing. Linear with no phase shift in the higher frequencies. An > interesting low frequency "afterimage" in the plot. (Not sure how else > to call this... Any thoughts?) > > 18569
Reading between the lines, the Pono DAC may have an Apodizing reconstruction filter. An Apodizing filter is based on the DAC's filter which is usually linear phase, or that has the same phase/amplitude response as a simple time delay. Based on sighted evaluations and questionable other listening tests, a sonic phobia about linear phase filters has developed in some people's minds. The focus of the phobia is ringing that comes before the impulse with a linear phase filter. The Apodizing filter adds additional phase shift to transform the filter response so that its phase response is more like that of a Minimum Phase filter which has all of its ringing following the impulse. Since actual evidence that linear phase filters > 20 KHz have any audible effects, the likelihood that an Apodizing Filter having any audible benefits is slim and none. One key concept that must be true, that many are in denial about, is that in order to have improved sound, there has to a sonic difference. Hence, testing for audible differences should precede testing for preferences. The ringing of reconstruction filters is often best measured with conventional time versus amplitude measurements. Impulse response of linear phase brick wall low pass filter: 18572 Impulse response of minimum phase brick wall low pass filter: 18573 It is well known that when the filter has a corner frequency that is well within in the audible range, difference between pre-ringing and post-ringing can be audible. With digital audio reconstruction or brick wall filters the challenge to audibility is the fact that ringing takes place above the normal range of hearing. +-------------------------------------------------------------------+ |Filename: 409Merfig02.jpg | |Download: http://forums.slimdevices.com/attachment.php?attachmentid=18573| +-------------------------------------------------------------------+ ------------------------------------------------------------------------ arnyk's Profile: http://forums.slimdevices.com/member.php?userid=64365 View this thread: http://forums.slimdevices.com/showthread.php?t=104094 _______________________________________________ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
