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In Reply to: RE: Jitterbug Measured Properly posted by jkeny on September 01, 2015 at 11:49:59
By changing the level of the up and down ramp where transition takes place
Follow Ups:
Have you looked at the effect of an LPF on rise/fall time - it can only lengthen them, not shorten them - hence my question.See the overlaid graphs of the eye diagrams with/without Jitterbug
If you take the threshold for 10 & 90% as about +/- 1.5V you can see that the time the graph takes to reach these levels is lengthened with the jitterbug in place.
Edits: 09/03/15 09/03/15 09/03/15 09/03/15
I think that they have taken a different reference; trace the risetimes they gave and look at the edges to identify the difference.
As for the Stereophile measurements, they were done in the analog domain (as far as I can see from your link) and the conclusion was:
''no significant effect that the JitterBug had on the analog signals output''.
Whatever the measurements, I have been quite surprised by the large SQ difference, ageing with the Stereophile observation about the mid high.
"I think that they have taken a different reference; trace the risetimes they gave and look at the edges to identify the difference."
That's what I did & it doesn't matter where you take the 10% 90% crossings, it always equates to a longer rise/fall time with the AQJB than withoutYes, Stereophile measure on the analogue output some slight jitter spuriae differences on the Dragonfly, just like HF&N do but no difference on any of 3 other DAC outputs
I'm not disagreeing that the is a SQ difference (although I haven't listened to an AQJB yet) but just that the measurements, so far are contradictory AND that the HF&N jitter measurements seem to be reversed - the edgerates are increased with the AQJB inline & not decreased?
Edits: 09/05/15
My reckoning is different. Superimpose their risetimes onto the horizontal axis from the starting point (bottom) and look at the top edge and you will see what I mean.
If you have an issue, why not email the editor?
The issue of the trigger point, which is what is important, has been an opaque subject for me.
I already posted a pic of the with/without eyepattern plots overlaid on top of one another & I can't see any possible way that this can be made to return a lower rise/fall time for the plot with AQJB. I think theory also predicts a lengthening of risetime with a LPF
I wanted to check my reasoning here first but you are the only respondent.
Sad that this forum (nor others) does not go into things like this, which forms the basis of digital audio reproduction performance.
Stereophile review & measurements here http://www.stereophile.com/content/audioquest-jitterbug-usb-noise-filter#dr35VQtKVSPuVgGs.97
"Conclusions
You can see from the "Measurements" sidebar that I could find no significant effect that the JitterBug had on the analog signals output by three of the DACs I had to hand. Yet with those DACs and others, I heard an improvement in sound quality that I can attribute only to the JitterBug. I hate when that happens!"
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