As one who has worked in the pro digital audio field for years, I can tell you that sub-100 ps jitter very definitely can be heard, depending on its spectrum. Modern sigma-delta ADCs and DACs use oversampling clocks of 12 to 50 MHz for sample rates of 44.1 kHz to 192 kHz at 24-bit resolution and achieve SNR and DNR of 120 dB or better, integrated over the audio range. The noise floor can be -144 dB or better and a 1-bit signal can be discerned. Higher-end consumer gear do use these as well as pro equipment.
David McGaw At 12:48 PM 10/6/2007, you wrote: >I have paid my dues in the HiFi world, but I have always insisted that >there be a solid scientific basis for any product I bought. > >When faced with claims that picosecond jitter can be perceived by >the human ear, my flim-flam-o-meter blows a fuse. > >A 1 nsec phasemodulation of a 44100 kHz clock signal will, worst >case, come out to an noise component 87 dB below the intended signal: > > 1/44100 [Hz] = 22.675 [uS] > 22.675 [uS] / 1 [nS] = 22675 [ratio] > 20 log(22675) = 87 dB > >And that is even assuming that the two relevant samples have >opposite signs, an impossible situation according to the Nyquist >criteria. > >I find such hifi-nut claims particularly ridiculous, considering >that every single loudspeaker on the market is designed in defiance >of how electromagnetism works. > >All amplifiers and loudspeakers on the market are designed assuming >that the task is to hold the voltage across the speaker terminals >proportional to the desired sound signal, despite the fact that >the magnetic field induced in the speakers coil is proportional >to the current, not the voltage. > >Who in their right mind will claim that they can hear a distortion >of -87dB, on speakers designed contrary to Maxwells equations ? > >And do I need to mention that very few rooms sport a S/N better >than about 50 dB these days, and that requires you to turn the music >up so loud that you are waaaay out of your ears most sensitive >range ? > >I'm totally with Randi.org on this one. > >Poul-Henning > >-- >Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 >[EMAIL PROTECTED] | TCP/IP since RFC 956 >FreeBSD committer | BSD since 4.3-tahoe >Never attribute to malice what can adequately be explained by incompetence. > >_______________________________________________ >time-nuts mailing list -- [email protected] >To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
