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 81 
 on: January 16, 2015, 11:23:51 am 
Started by Nick - Last post by PeterSt
Great stuff Nick. And thank you for sharing of course !

There's a word of caution though ...

With the clear notice that you announced part of it yourself already, I would be not so sure that you're looking at a signal decent enough to apply this analysis. This is two-folded :

1. The bandwidth of the analyser looks as if not high enough;
2. The grounding is the probe possibly is not in good fahsion.

Ad 1.
This is how you won't receive a square, which is the signal coming from the clock.

Ad 2.
This is how ground bounce may be injected in your analyser's signal.

In my view it can still be possible to observe as you do if only #1 is in order but #2 requires thorough real-time looking at the way the signal changes (when detected as error).

Of course, the "ground bounce" I'm talking about can be there internally (MoBo) just the same and this is how it requires real-time observation which I can't do (not being next to you I mean). So what it would require is "knowing" what can do it (from the MoBo's point of view) like for example a timer going on. Could be the Clock Resolution as we apply it in the software, but even with that in mind I don't think I would be able to do this because too indirect and complicated.
What I'm saying is that this wouldn't go for one such a "static" analysis, and that it merely requires a few different setups and then draw conclusions out of those. So like you suggested "one clock is better than the other". So, how ? And how does it show in the wave form ? And didn't you see already that by only changing the probes (detach and reconnect) changes the wave form ? I think you did.

Back to the bandwidth, I think you can also see how the shape of the individual cycles are (or can be) repetitive. Now this relates to the sampling rate of the analyser and here too, it requires real time observation. So think the analyser running on some clock rate and once in the xxx cycles all is the same again. Sadly the xxx can be millions, so again a tough thing to do (quite impossible, depending on what you see).

An example of what I mean could be the down-going slope in the first cycle in the rad circle, where the up-going peak will be detected as out of bounds. But now watch the remainder of the down-doing slope which is steeper than the others and now also runs out of bounds (near the bottom). And again in the middle of the dip where the next sample is now relatively higher because the previous one was captured too low. Just think that the average signal is represented, but the granularity of the X-axis (= time) is not high enough. How to combine this ? well, if the sampling rate (bandwidth) is not high enough, you'd get exactly this. First this peak is captured and because of that being at a too high level, the next one is additionally low (level). So because of the too low bandwidth the analyser detects an error here (could even be three for this one cycle) and you are happy with that ...

Of course you solve this by making the mask broader, as you btw already have done and now end up with 444 errors for the captured time period.
In the end you could be fooling yourself.
Additionally I'm pretty sure that if you set the mask broad enough, there will be no errors and then what. However, you could hope for a few per million which could be real error.

Lastly, I think I can tell you that no such thing as jitter can be observed from a wave form so deteriorated as this on one hand, and a time scale of 10ns (/div) on the other. Of course, you expressed it by means of error against the mask, but it is the same thing. However, still a bit dangerous to talk like this because such a "clock" can have 10s of ns of peak-peak jitter easily. But will depend on the specs for this (depicted by the MoBo) and you might know. Anyway the headroom you gave it looks to be ~5ns (black areas) and assumed the middle of that to be your target, any error implies 2.5ns deviation. And because it will happen at both sides of the set boundaries (other side for another cycle), it will be 5ns again, and more depending on the excursions.


Enough food for thought I think, and I can tell you that making a few comparisons like I suggested to make some better sense out of it, will require so much time (I think) that nobody is going to ask you to do it. But when you do I think we will be digesting it with much interest.

Regards,
Peter

PS, hints :
a. Always pick the very closest ground point you can find, near the signal (solder a small wire if needed).
b. Make the ground of the probe wire as short as you can. This means : wrap it right around the prope itself until left just enough for making the ground connection.
c. If you can incur for less/more error just because of changing b. somewhat, draw the conclusion that you can never get there (because it can always be better though up till physical constraints).




 82 
 on: January 15, 2015, 11:04:28 pm 
Started by Nick - Last post by Nick
So its looking like various clocks within the PC interact with sound quality and that improving these clocks significantly improves sound.

I thought to run the clock waveform of the high quality clock through a basic mask test on my scope.

What the test does is first record a continuous waveform of the CPU source clock into the oscilloscope's memory for about 1/1000th of a second so in total about 25,000 clock waves are recorded. It is then possible to apply a test "mask" (see the blue area in the trace below which is incidentally a massive deviation for a clock signal)  to all of these waveforms so that the analysis captures each time a wave form shape deviates from unshaded area into the blue mask.

The wave form of a clock should be rock solid and not deviate all. When the clock being tested is captured without the PC turned on, sure enough the clock always stays within the mask and no errors are recorded.

With the PC turned in it is a very different story. The trace shows the capture analysis. The red circle shows one of the wave form errors picked up by the mask. In clock terms the wave form disruption is very large. That is really going to add jitter and phase noise.

Look now at the blue and red dotted lines at the bottom of the trace (see the lines between the white "1" and "2" in the image at the bottom). The trace from 1 to 2 in total represents about 1/1000th of a second in time. Every red dot on that line represents an error wave form that has strayed into the blue mask. This capture which is a typical one shows 444 errors in 1/1000 of a second. This equates to an average error rate just under 2 clock beats in every 100 !!

(Just as a note the trace shape shows reflections, due to the measurement point of the signal the wave form injected to the PC mobo is better.)

So this is driving thinking on further modification to the PC along another direction that I had hoped would not be necessary. I guess it is a case of how far you want to go, the sound quality so far achieved is very very nice, its just when you see this it points towards the possibility of more improvements.


Nick.


 83 
 on: January 15, 2015, 06:35:14 pm 
Started by CoenP - Last post by PeterSt
To those concerned :

I just sent an email with a new driver and which works. Ehm if I tested all decently this time. Wink

Small problem, this one too has version 2.0.8. But per instructions in the email you will be fine.

Peter

 84 
 on: January 15, 2015, 04:18:41 pm 
Started by PeterSt - Last post by PeterSt
Anthony - Yes, I'm afraid so. But what's the difference with damping/footers under the DAC and other gear ? Persoanlly I think we shouldn't be hyped because now I started with this and created a topic for it. Of course, I try to have some reasoning along with it, but I surely shouldn't be regarded as someone who found something new and it now needs further exploration. All I say is that it matters (even quite a lot) plus that I don't know how to control it. Or at least not in general fashion (working out for everybody I mean).

Meanwhile my change from now over a week ago is still in and I still hear the virtues of it. Btw I think it is on the edge of too much snappyness but I wouldn't know how to make that less (or more for that matter). Of course all it takes is putting some different matererial under it but since I don't see the sense of that (which could be telling you what to do), why do it. May come across as too negative but it is and remains so that I never do anything for myself only here and I rather not create a "Yahoo!" for myself because I would have psychological problems with not being able to share.

But isn't it enough if you guys yourself know that you can experiment ? Or did you but didn't hear a difference (and don't tell about it ) ?

During typing another (related) experiment slipped into my mind. So maybe I will apply that and report about it ...

Regards,
Peter

 85 
 on: January 15, 2015, 12:06:02 pm 
Started by PeterSt - Last post by acg
Ok, I understand that but what is the way forward?  Just stuff and stressed "sandwich" under the pc and some soft springs under the sandwich to damp frequencies under 5hz or so?

Is listening the only way to quantify a change in SQ?

 86 
 on: January 14, 2015, 08:39:17 am 
Started by PeterSt - Last post by PeterSt
Hi Anthony,

Measuring of jitter as you suggest of course is possible, *if* I had the gear for it. And I have not; too expensive (think 150K+ euros for the jitter levels we talk about here).
Otherwise I am under the limits of the scope I use for it (3ps) so nothing much more to do at his moment but listen.

In my view you are correct about the footers and when they become "tweaks". This is why I never like to experiment (still did not change a thing since) and rather reason out the exact "how". Well, you know. But I really can't do all at the same time so we must be patient somewhat.

Thanks and regards,
Peter

 87 
 on: January 13, 2015, 10:39:21 pm 
Started by PeterSt - Last post by acg
So, first question regarding your jitter images in post #3 above.  Can you be sure that your exercises did not affect the measuring equipment as well as well as the dac?  Or perhaps one more than the other?

Hi Anthony - very good point. And of course I can't tell with 100% guarantee. All I know is that the scope was on a very large kuschen for the purpose.

Keep 'm coming because mistakes are made so easily !
Peter

Second question Peter.  Is it possible to "measure" the jitter for the different PC damping solutions to get some idea about the relative contribution of various vibrations to the change? Such as the two images you posted above...although it would be ideal to be able to generate a histogram on the jitter spectra rather than rely on the fuzziness of the line on the scope.

Perhaps change one variable at a time: usb cable routing and type; proximity to the soundroom; various types of "damping" et cetera.  I know that is a lot of work, but it is a nice linear workflow that may be able to shed light on which vibrations matter.

As as aside, your observation that softer damping of the PC works best seems to correlate with the idea of removing or minimising low frequency vibrations from the floor/rack.  Softer damping generally means that lower frequencies are absorbed by the damping.  Harder footers probably serve more of a "tuning" function and in my opinion based on my limited knowledge of this subject those sorts of "tuning" footers are "tweaks" rather than solutions. 

Cheers,

Anthony

 88 
 on: January 12, 2015, 01:45:36 pm 
Started by Nick - Last post by christoffe


Very very very  Happy .... and more to come.

Nick.

Hi Nick,

the conclusion will be, that we have to select an appropriate/suitable motherboard (for all of us) and send this to you to implement your sophisticated modifications.

Joachim

 89 
 on: January 12, 2015, 01:38:24 pm 
Started by Nick - Last post by manisandher
I just cannot believe how utterly broken a PC is for high quality music replay until it is "fixed".

Well, just playing around with PCIe/PCI USB cards over the weekend (and USB cables over the holidays), it's obvious to me that there's still so much to be done. And you're at the vanguard of it all!

Mani and Paul are over this weekend so it will be interesting to see what they make of the sound..

Yep, really looking forward to it.

Cheers, Mani.

 90 
 on: January 12, 2015, 01:21:00 pm 
Started by Nick - Last post by Nick
The fireworks in my earlier post when the PCIe clock was fitted were just a small amount premature. ....

So a further update and to say its good news is somewhat of an understatement  Happy

The high quality clock was put into by PC to replace the lashup clock that I reported on above. The result are spellbinding and the [fireworks]


 Happy new year ! Happy new year ! Happy new year ! Happy new year ! Happy new year ! Happy new year !


are now official with bells and whistles on haha.

The new clock has only a couple of hours on it so it will significantly improve as it runs in but this is a no brainer of the first degree.

I will post more considered notes again when the clock has run in and I have had chance to properly setup the system [there is tuning to do that has not even been applied yet]. Iíve been researching what might be going wrong in the PC for a long time now and with all of the experiments over the last months can now target areas of the architecture that need to be "fixed", apply the fix and predict the results before hand with reasonable accuracy. In addition this is meaning that time is not getting wasted on stuff with limited payback potential. Parts for the next round of developments are on order but coming from China so frustratingly slow.

I just cannot believe how utterly broken a PC is for high quality music replay until it is "fixed". There is so much more to come Iím sure of more gains just need those dammed parts !

Mani and Paul are over this weekend so it will be interesting to see what they make of the sound..

Very very very  Happy .... and more to come.

Nick.


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