bluegaspode;694522 Wrote: > Well sorry to be playing devils advocate here. > But right now I read the argument as follows > > a) there is a theorem which proves that under ideal (in the realworld > not achievable) conditions a sampling frequency of x will be good > enough > b) we use some totally different process to do the reconstruction but > still refer to the theorem and claim that it still applies. > > For me this sounds like comparing Apples with Bananas. > > Or to put it differently: > > Mr. Dan Lavry begins his document with the statement: > > (sorry I didn't have time yet to read the paper to the end, will do it > later). > > And quite opposite to this statement a quote from Wikipedia about > Nyquist: > > > > So as the preconditions of the theorem cannot be met (according to > Wikipedia, sorry I don't have better source nor knowledge) I think it > is a valid question if we can overcome the (possible) deficiencies with > higher sample rates (or other means). > > So for me this part of the argument has its flaws (while of course I'm > very happy to believe all the other proofs which include double blind > tests) It is trivial to show that the error inherent in the process is below the range of detection. A computer-generated sine wave dataset (I.e. not recorded via an ADC) can be passed through a DAC and null-compared. I've done this and the result should be no surprise to anyone. PS don't try this with a nos DAC!
The human ear/brain also operates on a sampling basis (there's nothing "analogue" about the ear by the way) and uses a reconstruction filter just like a DAC to integrate the discrete samples into something we can understand. What some people are misunderstanding here is that it is the reconstruction filter that recovers the analogue signal, not the DAC. The DAC simply presents the filter with a set of voltages over time. It is within the filter that the sinc function becomes manifest and this is indeed an infinite series - the mathematical definition of a filter is a continuous function over time. A filter is not a step function! To be clear on this, what comes out of the filter IS a mathematically perfect sine wave... All the way up to the Nyquist frequency. This is both predicted by the theorem and demonstrable in practice. There is no known way to differentiate between a 1khz sine wave sampled at 44.1 or 192. In every conceivable way of " measuring" or analysing that sine wave it they will be indistinguishable. What is true for one sine wave is also of course true for any combination of sine wAves (or as we usually refer to it... Music). Or do we need to have a conversation about Fourier transforms and the practical implications of mathematical infinite series as well? Now there IS a way to break this model. Try a perfect square wave!. This has to be done using a mathetmatically generated waveform/data set because it is impossible to generate or record a perfect square wave with infinite rise/fall times. The filter will introduce non-linear ringing. This is all predict by the theorem because an infinitely fast slope requires an infinite number of samples... I'm sure you get the idea. Bottom line is this; for real world sound distribution 44.1 is fine ... Which is why there are many many fine sounding red book CD's... And why there is no published evidence that stands scrutiny to support the idea that anyone can tell the difference between the same master distributed and played back at 192 or down sampled to 44.1. -- Phil Leigh You want to see the signal path BEFORE it gets onto a CD/vinyl...it ain't what you'd call minimal... Touch(wired/W7)+Teddy Pardo PSU - Audiolense 3.3/2.0+INGUZ DRC - MF M1 DAC - Linn 5103 - full Aktiv 5.1 system (6x LK140's, ESPEK/TRIKAN/KATAN/SEIZMIK 10.5), Pekin Tuner, Townsend Supertweeters,VdH Toslink,Kimber 8TC Speaker & Chord Signature Plus Interconnect cables Stax4070+SRM7/II phones Kitchen Boom, Outdoors: SB Radio, Harmony One remote for everything. ------------------------------------------------------------------------ Phil Leigh's Profile: http://forums.slimdevices.com/member.php?userid=85 View this thread: http://forums.slimdevices.com/showthread.php?t=93990 _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/mailman/listinfo/audiophiles
