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In Reply to: Lynx and RME cards. posted by Presto on April 16, 2007 at 20:16:02:
Dan Lavry and others had a long discussion of this issue over at PSW recording forums. It appears that there are issues with wordclock cables and terminations, with reflections causing jitter. Lavry argued that improvement from an external clock implied that the internal clock was defective.
Follow Ups:
Just carrying clock over a wire means it is now susceptible to all sorts of jitter causing issues.What's even worse is that the device accepting a word clock input may need to use PLL to recover the clock and to filter out jitter caused by the signal transmission.
The end result is certainly no better than an internal clock, and may not even be better than a clock recovered from SPDIF.
The saving grace is that the DAC can rebuffer the data knowing that the signal can be synced back to it's master clock. However, not all DACs that send word clock out do this.
Christine,
Do you mean to say that equipment such as the dCS and external Verona clock is a waste of time (ignoring the cost issue)?Reviews seem to indicate that using the external Verona clock with the other dCS gear sounds slightly better than slaving the transport to the DAC, which in turn sounds slightly better than slaving the DAC to the transport, which in turn sounds slightly better than the DAC recovering the clock form the signal stream.
Of course, studios use clock distribution because they have to sync multiple devices to a single clock.For the audiophile, it seems to be another unnecessary part of the chain. I like keeping things simple.
Also, I question the whole assumption that PC's always have jittery clocks in them. A good soundcard should have power filtering in it so this wouldn't happen.
At least, there is a tradeoff between the jitter on a card from this clock, and jitter induced by S/PDIF or USB transmission. There ain't no free lunch.
*** Of course, studios use clock distribution because they have to sync multiple devices to a single clock. ***Not really true anymore. Very few studios do clock syncing, because these days you can do almost everything onboard on the DAW. And there's no need to sync incoming digital signals to the DAW because they get buffered anyway. Time stamping (via SMPTE) is more important than syncing.
The main issues with PC are logic induced modulation and EMI. It is possible to mitigate against these issues, but never completely.
What would be the most-cost-effective method to attain a transport that can be slaved by the DAC's master clock? I have a DAC that is master clock ready, but just need a transport that I can synchronize with it. Thanks again.
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