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In Reply to: RE: Thanks, but could you please elaborate on... posted by John Marks on April 22, 2016 at 13:25:57
The same bits can be conveyed by slightly different waveforms due to noise and timing issues associated with the transmitter at the transport, the digital cable, or the digital receiver in the DAC. In an ideal world, the digital receiver in the DAC would correctly interpret the bits and would eliminate all of the noise and timing issues. In the actual world, this does not happen and some of the variations make it to the analog output of the DAC.
Here are two strings of bits that are the same, but are physically different on the screen:
0 1 0 1 0 01 0 1 1 1 01
0 101 0 0 1 0 1 1 1 0 1
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
Follow Ups:
Dear Tony,
Thanks.
I think then we are using different terms for the same thing or the same constellation of phenomena... .
I believe, as apparently you may also, that suboptimal terminations (including the wiring behind the panel jacks, either RCA or BNC) can result in reflections such that when the reflection makes a round trip and comes back to the DAC, the reflection can degrade the timing accuracy of a later-dispatched signal.
(BTW, if this is the case, then should we not want higher-loss cables rather than lower-loss cables? If the cable were not capable of carrying those micro-level reflections back and forth, would not the Digital Eschaton thereby be Immanentized? Only half joking.)
I believe that cable length is an important factor in determining when the reflection arrives with respect to the zero crossings of the later-dispatched signals, which is why I do not offer cables in lengths such as half a meter and one meter.
I do have to tell you though, and I am sure that this will be no news to you, that more than one engineer has told me that if a DAC cannot cope with such small levels of induced jitter, it was either incompetently designed or is broken, and therefore all properly-fabricated, non-broken digital cables sound the same.
ATB,
John
"I do have to tell you though, and I am sure that this will be no news to you, that more than one engineer has told me that if a DAC cannot cope with such small levels of induced jitter, it was either incompetently designed or is broken, and therefore all properly-fabricated, non-broken digital cables sound the same."
This pretty much covers every DAC that has ever been made, although few designers seem to be honest enough to admit this applies to their products. There is another side to this. Even if such a DAC were to be made, there would be few subjective audiophiles honest enough to admit that they could not hear any differences caused by digital cables.
Removing noise from digital signals is well understood in the field of military electronics, where it is needed in encryption devices that must keep separate "red" signals corresponding to classified information from leaking into "black" signals being sent over cables or airwaves. If as much money flowed into high end audio as flowed into military electronics our problems with digital cables would have long been solved.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
If the Pentagon were given this problem, we'd spend a decade and many millions funding contracted R&D projects to evaluate alternatives, a couple more years and millions arguing and negotiating over requirements, a bunch of competitive prototypes demonstrated, a source selection, a protest of the result, a development contract eventually awarded to productize the winning interface, the result would be unaffordable for its original purpose, other companies wouldn't adopt it because they hadn't invented it, something would get produced if for no other reason to show some return on the investment, but by the time that happened it would already be obsolete. Don't ask me how I know this :)
nt
I don't believe any of the "variations" can me be measured in any way at the analog output of the DAC.
And if what you are saying not simply wonky theory, then the market it littered with broken digital cables, transports, and DACs.
I don't believe any of the "variations" can me be measured in any way at the analog output of the DAC.
They are routinely measured. Ever seen a jitter test?
These variations can be, and have been, measured on the analog output of DACs. Usually when this has been successfully accomplished the measurements or experimenter have been discredited or the equipment under test decreed to be defective.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
"..when this has been successfully accomplished the measurements or experimenter have been discredited or the equipment under test decreed to be defective."
Can you cite specific examples of this please.
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