|
Computer Audio Asylum Music servers and other computer based digital audio technologies. |
|
|
|
Computer Audio Asylum Music servers and other computer based digital audio technologies. |
|
In Reply to: RE: Single Clock Domain. Otherwise madness! posted by Tony Lauck on March 28, 2012 at 09:40:45:
"I suggest you look at some sample circuit diagrams for a typical gate. One such involves two pull down transistors with their output in parallel connected to a source via a pull up resistor."
In general OC gates (oh I know, open drain nowadays) are only used if you want to do a dot-OR or a level conversion, they aren't typical. However this structure may be more common internally since the parasitics are low and controlled.
"So the output of the latch will also be fluctuating slightly with the input signal, even if there is no clock pulse to enable the gate sufficiently to "change" the state of the latch."
Nope, that's not the way it works. The input is "decoded" at the trailing clock edge and the if the levels are within spec latches the state properly. After that the input can do whatever it feels like and the output doesn't care. The output will fluctuate due to rail variation and a tiny amount from common impedances but will be way within limits. The symbol has been decoded and reconstructed and is now independent of the input.
"This means that at roughly the same time stage N is being loaded the voltage on one of its gates may be fluctuating due to slight leakage through the unclocked stage N-1. It is reasonable to assume that this will affect the rate at which stage N latches into the new state, but here the circuit design issues will be less obvious."
Actually they are pretty obvious but they don't matter. The whole beauty of using a clocked data scheme is to make sure that you don't try to decode the symbol until the inputs have settled.
"This is something for a circuit designer with mixed signal expertise to carefully consider."
In process.
"It is possible to conduct experiments to distinguish whether propagation comes through the signal path vs. through power and ground."
Yes, you can conduct the experiments but the answer is already known: both. "logic levels" only have local validity and must be decoded with respect to the local plane. At the slicing point, whether just level driven or also gated, the signal and reference are compared and a decision made. If something is screwed up and the differential level is between the valid bands then the system falls into the category of broken. Bear in mind that this is all local stuff and we aren't trying to decode long-hauled signals with all the distortions and deprecations that they are prone to.
"Any jitter or AM modulation will appear at this point and using synchronous averaging it will be possible to correlate any coupled noise to a very low level by measuring over a long time period (very narrow frequency band)."
Now your talking! Synchronous demodulation is just magic but I don't think you need the second board since I believe all that matters is the voltage differential. If you sync to your injected noise you can measure how much it's attenuated with a storage scope or you can just use a spectrum analyzer since, being the god of the experiment, you will of course have chosen noise with a unique signature.
"The key to these experiments is some reliable means of detecting when sonic pollution is occurring."
AMEN! If you can't measure the output or force the input it takes a ton of patience to sort stuff out if it's possible at all.
"Note that even if complete isolation of all forms of input noise is provided by a DAC, it is likely that some audiophiles would still complain that there was an effect."
True, but there are other factors that can confuse the issue and it's impossible to ever achieve complete isolation of anything. If an ant farts in Texas it affects the orbit of Mars just a little... The best you can hope for is to get the stuff that you are trying to control to have a small enough effect that it's masked by something else. Thank God for Brownian motion!
"This likelihood [unhappy audiophile] provides strong demotivation for me to investigate this in detail or to get involved in the business designing and producing high end audio gear, for that matter. :-("
Oh... So that's why DEC is no longer around, they finally had an unhappy customer? Most manufacturers have fairly broad shoulders and I would suppose those in high-end home audio must be especially well quipped since their fancy gear can be brought to it's knees by so many, many factors out of their control...
Good listening! Hey speaking of which I'm quite interested in your (new?) speakers, how long have you had then and how do they do without the sub? Prolly should be another thread I suppose.
Regards, Rick
This post is made possible by the generous support of people like you and our sponsors:
Follow Ups
- RE: Single Clock Domain. Otherwise madness! - rick_m 07:48:38 03/29/12 (1)
- RE: Single Clock Domain. Otherwise madness! - Tony Lauck 08:14:15 03/29/12 (0)
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2024, Audio Asylum, all rights reserved ]
