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In Reply to: Re: We are not connecting here posted by Charles Hansen on March 4, 2007 at 16:50:26:
HowdyBut that is exactly my point: that isn't a mistake it's reality. A FIFO doesn't make things perfect, tho it usually helps. A FIFO is a jitter filter not a jitter eliminator. The point of the author of the diagram is trying to make (http://audio.peufeu.com/node/7) is that using a DAC sourced clock to drive the transport and also to reclock the returning data helps to solve a lot of the S/PDIF problems (but not eliminate them entirely.)
Anyway I don't believe in gremlins and it's obvious to me that jitter is the cause of the problems that you are attributing to gremlins :)
I was encouraged as I looked for the links I gave that more and more universities are adding sections to their EE courses about jitter. I was taught a little about it back in the late 70's but I haven't run across too many hardware people with formal training in jitter mitigation.
Follow Ups:
< < A FIFO is a jitter filter not a jitter eliminator > >So just to make sure we are on the same page here, please explain to me what you think is the mechanism for jitter to be passed through an *asynchronous* FIFO.
< < I don't believe in gremlins > >
I've didn't used to either. But I've seen so many things make a clearly audible difference that (according to all currently understood electronic theory) *shouldn't* make a difference, that I've resigned myself to the fact that are things that we just don't understand yet. If you want to call those "gremlins", that is certainly your prerogative.
HowdyI'm not sure why you highlight asynchronous in this case, but as I've stated it before, things like local grounding levels being affected by the input clock and data affecting the output clock's levels/timing.
Anyway we've beaten this to death, I'm just as baffled about your point of view as you undoubtedly are about mine :)
Perhaps this is similar to the situation where there are some who claim that cables can't make a difference. It's clear to me that they do and I believe that in principle we can explain those differences, but in practice predicting the sound of a given cable with, say a given amp and given speakers is fairly intractable. Especially since we don't have that accurate of models let alone knowing how specific measurable features sound. Still I don't believe it's magic, just difficult.
< < I'm just as baffled about your point of view as you undoubtedly are about mine > >Referring to the block diagram I previously linked to, I guess what you are saying is that there is NO WAY to make the master clock immune to jitter on the incoming data signal, and that it is this transfer of jitter that causes various transports to sound different.
And I guess what I am saying is that it IS possible to make that master clock be totally immune to jitter on the incoming data signal. And that furthermore, we would still be able to hear the differences between transports because there is some other factor involved besides simple jitter.
I can't really think of a way to test either theory. All I can say is that whenever I found a really good way to test things that didn't make any sense whatsoever, they still made a difference. To the point that I'm pretty sure that are *lots* of things we still don't understand. Hence my original statement that I wish the "answer" was as simple as "jitter".
Thanks for keeping things civil!
Howdy"Thanks for keeping things civil!" and to you too. I sometimes dread reading and responding to posts when I'm challenged. I thank you especially for your last post and I agree with your synopsis of our positions :)
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