ralphpnj wrote: > Thank you Clive for that very clear and thorough answer and also for > reminding Arny that I was, indeed, only joking about the audible effects > of tagging. > > Based on what I've observing it would appear that jitter is now > replacing "clean power" along with several other audiophile bogeymen as > the newest in the ongoing line of audiophile bogeymen. I guess even fake > cures need fake illnesses for hem to be effective (where "effective" > means the ability to make people part with their money).
Excellent discussion guys! Jitter has been a bogeyman for years... As far as I recall, it was always the "digital sucks" poster boy from the 80's. For example, here's Stereophile from 1992: http://www.stereophile.com/reference/193jitter/#LLFxUQ3vMHFGhd4t.97 As others have noted, it began with the SPDIF interface which embeds clock data within the serial data stream, thus the "transport" device's clock accuracy could be questioned and clock recovery and timing reconstitution whether by PLL, ASRC, buffering were utilized to smooth things out for the receiving DAC. So we could say that in the SPDIF days, the transport and DAC both have roles in maintaining clock accuracy. With the advent of true asynchronicity with async USB and ethernet these days where it's just data transfer with bidirectional flow control, the onus is on the DAC itself if we see any kind of timing/jitter issue. Here's Ethan Winer and discussion of jitter manifesting in the analogue output as FM modulated sidebands: http://ethanwiner.com/audibility.html And those sidebands are of course what the Dunn J-test is about. In testing, it's not difficult to find them in most all SPDIF transport-DAC combinations but they really are -imperceptibly tiny- in the vast majority of cases with sidebands <100dB below the primary signal and in real music would easily be masked by the sound or buried deep in a typical recording's noise floor! With an ethernet streamer like the Squeezebox systems (Touch, Transporter) there's no issue at all... Likewise async USB remains clean unless the DAC itself is clocked poorly. BOTTOM LINE: 1. Jitter is by and far an inaudible phenomenon in today's systems. Only the foulest of "audiophile" designs raise eyebrows like this Zanden 5000 Mk.IV: http://www.stereophile.com/content/zanden-5000-mkivsignature-da-converter-2000-premium-cd-transport-measurements#QVhaxZEDAmVy7kBc.97 2. Sure, SPDIF digital interfaces and obsolete adaptive isochronous USB interfaces can show higher jitter-related anomalies with measurements than asynchronous ethernet/USB. Again, measurable anomalies do not mean audible. 3. Anyone who cares so much about timing and jitter should have a good look at vinyl wow & flutter - orders of magnitude worse! Yet somehow audiophiles turn a blind eye on this but pick on jitter as being something terrible! [Here's 'my fun look at using the vinyl PlatterSpeed app with digital' (http://archimago.blogspot.ca/2014/09/measurements-digital-audio-and.html), compare it with 'this link of the Technics SL-1200 turntable' (http://archimago.blogspot.ca/2014/08/measurements-technics-sl-1200-m3d-wow.html)...] 4. The recent advent of the JitterBug and UpTone's USB Regen is more on the same theme... Neither have released any useful technical information to show they work. In fact, measurements for the JitterBug in 'Stereophile has suggested no effect' (http://www.stereophile.com/content/audioquest-jitterbug-usb-noise-filter-measurements) and the eye pattern published suggests 'worsening rise time' (http://www.whatsbestforum.com/showthread.php?18311-AQ-Jitterbug-Measurements/page20). All reported benefits seem to be either from company representatives or testimony (like John Atkinson's). And of course 'lots of talk about Regen' (http://uptoneaudio.com/pages/j-swenson-tech-corner) with still no objective evidence. Oh, BTW, 'here's Mark Waldrep's testing with the Regen' (http://www.realhd-audio.com/?p=5150). Predictably, -nada -according to him but there were some other followups with folks who thought they did hear something... Alas no actual controlled ABX'ing I think. The arguments rage one... Fun times :o. Archimago's Musings: (archimago.blogspot.com) A 'more objective' audiophile blog. ------------------------------------------------------------------------ Archimago's Profile: http://forums.slimdevices.com/member.php?userid=2207 View this thread: http://forums.slimdevices.com/showthread.php?t=104340 _______________________________________________ audiophiles mailing list audiophiles@lists.slimdevices.com http://lists.slimdevices.com/mailman/listinfo/audiophiles
