Andrew L.Weekes said the following on 02/01/2006 00:16: >>Interesting. What is the equations that describe this? >>If it is too long to post, got an URL? > > > SNR (DBC)=–20 LOG10(2π.FIN.TJITTER), WHERE FIN IS THE > ANALOG-INPUT FREQUENCY, TJITTER IS THE TOTAL SYSTEM JITTER IN SECONDS. > > Immediately it should be clear that the fIN factor gives result > dependant upon the sampled frequency, using the figures mentioned, > 20,000ps gives, assuming no other system errors, 98dB dynamic range > (non-dithered CD spec) at 20Hz, but only 51dB at 20kHz. > > 100pS would meet the 20kHz non-dithered spec, but what about dithered > input signals? > > Factor in a 15dB additional dynamic range from a properly dithered > input signal, or a 24bit system (or worse still, a wide-bandwidth > system) and you can see things rapidly becoming much harder. > > It's one reason why the newer, hi-res formats fail to live up to my > expectations, they make the engineering, which is already bloody > difficult, MUCH harder. > > It really isn't as easy as many so called 'experts' make out, jitter > isn't that easy to measure (to the man in the street) and even when one > can, it's not as simple as a headline figure. > > The recent volume rounding error problem of the Squeezebox gave rise to > an error at the 16bit of the audio data - so many experts would tell you > this is inaudible, yet people here (without knowledge of any change) > found it wasn't. > > The human ear / brain interface is a really astonishingly complex > thing, that can at one and the same time be both amazingly sensitive, > yet easily fooled. What it isn't is measurable, in any quantitative > manner. No-one, anywhere, with any experiment or test, can 'prove' the > absolute audibility or inaudibility of anything when it comes to music. > Realising that is crucial to avoiding the often prolonged debates that > happen around these subject areas. Whilst the maths above, for example, > explains a mechanism for audibility, it tells you nothing at all about > an individual's ability to hear the effects, there are few absolutes of > 'audiblity'.
Amen. Andy has articulated my thoughts on this matter much more clearly than I could ever be bothered to write down! R. _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/lists/listinfo/audiophiles
