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In Reply to: RE: It would be a deal-breaker for me indeed.....to this reviewers credibility. posted by Thorsten on January 02, 2015 at 19:22:16
Mains related side-bans are jitter.
It is different from noise at 60Hz, 120Hz, 180HZ, 240Hz, . . . . . .
Follow Ups:
Hi,
Jitter is clock related.
These side-bands with a fair bit of certainty (if not 100%) do not come through clock contamination, but from simple analogue noise.
So they are not jitter in the literal sense of the word.
Unless we re-define "Jitter" to mean "any noise from any source", in which case we no longer need to treat jitter separately and instead can subsume it under THD&N...
Ciao T
At 20 bits, you are on the verge of dynamic range covering fly-farts-at-20-feet to untolerable pain. Really, what more could we need?
. . . . .
Power supply related noise can disturb clock.
If the disturbance has some periodicity, there will be sidebands.
....how many DAC's have you measured, for example for jitter? One does not need an AP2, ULP or dScope for that either (though something better than a 3rd octave RTA is needed in most cases)?
What you dig out is old news to me. And I will repeat, from experience the most likely cause of the results measured is not actual jitter, not PSU noise disturbing the clock or any of this, it is a simple and old fashioned operator error by the person setting up the measurement.
And I got that experience by making similar mistakes on occasion and learning to avoid repeating them subsequently.
I understand that you do not like my conclusions and that you want desperately believe that the particular test is not in error (even though alternative tests that fail to show the same problem exist in the public domain.
But honestly, that is your problem, not mine.
Ciao T
At 20 bits, you are on the verge of dynamic range covering fly-farts-at-20-feet to untolerable pain. Really, what more could we need?
I think your claim is completely wrong.
If the measurement set up invites so much 60Hz, 120Hz, 180Hz, 240Hz, . . . . . noise so that it can cause such a high jitter from a non-defective well-designed hi-fi DAC,
it is impossible to have this graph: THD at 0 dBFS (2.2V RMS), 22kHz measurement bandwidth.
Hi,
> If the measurement set up invites so much 60Hz, 120Hz, 180Hz, 240Hz, . > . . . . noise so that it can cause such a high jitter from a
> non-defective well-designed hi-fi DAC,
>
> it is impossible to have this graph: THD at 0 dBFS (2.2V RMS),
> 22kHz measurement bandwidth.
Please, based on your understanding of the R&S ULP analyser and the specific way the above measurement (note it is THD NOT THD & N) is operated, provide an adequate explanation as to why mains related hum would show up in the test you reference.
Ciao T
At 20 bits, you are on the verge of dynamic range covering fly-farts-at-20-feet to untolerable pain. Really, what more could we need?
If there is high level 60Hz signal, how can it have low THD at 20Hz?
"The effect of power supply ripple on jitter is quite straightforward."
Silicon Laboratories Inc.
http://www.silabs.com/Support%20Documents/TechnicalDocs/AN491.pdf
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