Quote:
Originally Posted by nas  I plan on upgrading my front end with a Mytek Stereo192 AD and will have a MOTU 828 mkI slaved to it through the SPDIF. I'm bypassing the 828 converters and just using it as a FW audio interface. My question is will clocking the 828 to the Mytek improve the sound quality of the 828's DA because it is locked to a more stable clock? is this something that is quite noticeable? |
There is an
extraordinary amount of outright misinformation and pervasive misunderstanding of this issue.
Slaving a given converter to an external clock source virtually always tends to
increase jitter (irregularity of sample timing).
Slaving to an external clock source
does not remove a supposedly 'inferior' clock circuit from the process -- indeed, the converter's internal clock circuit is STILL the source of internal timing -- but NOW it must do the much
more difficult job of continually trying to maintain sync with the external clock by a phase locked loop.
This is
more difficult than simply keeping good internal time. And --
crucially -- it tends to
increase jitter, which means
decreased sample accuracy (the samples are measured at the wrong point in time).
So, why do so many people have this strange notion that trying to sync to an external clock can
improve sound?
Good question. Much of the problem relates to a marketing campaign by a certain mid-high level maker of converters and external clocks (external master clocks
can be helpful in big rigs, since even thought he
best option is often to use the clock in the 'lead' converter for the master, it
can be more convenient to have a central clock with multiple i/o options).
This campaign featured a number of celebrity endorsers who claimed their rigs "sounded better" simply from being slaved to Brand X (or should I say
Brand A?) master clocks. The company says that THEY never claimed that but that they have many endorsements for people who say it's so.
But that company has since backed away from some of the more outrageous claims and now says that those who want to buy one of their master clocks simply looking to improve the sound of a converter should simply buy one of their converters instead. (Which makes considerably more sense, at least if one thinks their [quite well-liked] converters are worth the moderately substantial buy-in.)
Anyhow, if you want to read a LOT about the issue, there's a mammoth thread that involves many heated exchanges between digital design legend Dan Lavry and some other heavyweights arguing againt a number of "true believers" and even some representatives from the unnamed manufacturer above:
PSW Recording Forums: Dan Lavry => Proper word clock implementation But... why do so many people
think their converters "sound better" if the jitter is almost certainly greater?
Both Dan Lavry and Digidesign's tech staff (in a white paper they wrote on the issue) have suggested that these folks are either
fooling themselves (precious few seem to have pursued double blind ABX testing) or that these folks may simply
like the distortions produced by jitter.
Digidesign white paper on external clocking and jitter:
http://akmedia.digidesign.com/suppor...er_J_33269.pdf