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In Reply to: Master/Slave Relationship posted by rps on May 15, 2005 at 12:24:14:
as I understand it, the Pro Audio uses the independent master clock , as a master, and both DAC and digital source and whatever else as the slaves. Nowhere it says that 'DAC must be a master and source must be a slave'. In master-slave relation whoever has the better clock should be a master. In the absence of information 'who got better clock', it's better not to have master-slave relationship in a first place, and this is what majority of consumer digital products do. Some semi-pro transports and DACs are designed to act as a slave to some external master clock. Of course, having the option in CD transport to act as a slave for some external clock won't hurt --- but then you won't find DACs which act as a master (well, with an exception of lessloss, of course, and may be a few more). I guess manufacturers simply assume that having the external master clock driving both DAC and transport is a PRO setup, and they don't expect a regular customer to use such a setup.
Follow Ups:
What prompted my inquiry was a blurb from the LessLoss Audio Devices company that was posted under 'Manufacturer's Viewpoints' on enjoythemusic.com web site (Myths and Misconceptions About CD Players and DACs). The blurb concludes..." You only need to slave the transports to a DAC in Digital Master Mode." ...to achieve the same sound as a $30k player. If it sounds too good (pun not intended) to be true, then it usually is.I guess if it were as simple as LessLoss proposes, we would have a standard in dacs.
http://www.tnt-audio.com/clinica/diginterf1_e.htmlon TNT-audio. The author is DAC designer, and he's not trying to sell you anything. The whole thing has 5 parts, read at least this one, and, more importantly, the next which takes about different designs in terms of master-slave, in consumer audio (vs pro audio).
So apparently there *are* some benefits in having master clock sitting in a DAC in home audio, the major reason is that there is too many things going on in transport which possibly affects the quality of transmitted signal (and in the regular, non I2S type of connection a clocking information is embedded into the data). Yet apparently having DAC acting as a master clock introduces its own problems that must be solved. He talks about Wadia. Also he talks about Linn which apparently does something yet more complicated, like transport and DAC part constantly talk to each other back and forth. He also discusses I2S as a clean way to use transport as a master, since the clocking information goes throught the separate wire and there is less potential for its distortions. Makes interesting reading. He mentions that Philips had a patent on I2S, but recently that patent got expired and I2S is now in public domain.
But back to having the DAC acting as a master clock, apparently there are some special considerations involved, and without proper design there are side-effects. Frankly, if there *is* a magic bullet, I think it's I2S and high-quality clock on transport.
But once again, Pro Audio normally uses separate master clock which gets distributed to multiple slaves. I think dCS has something like that, with respect to high-end home audio.
Thanks for the referral. To clarify, I was not interested in pro audio products per se; it was LessLoss that mentioned pro audio and master clock/dac.
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