DeltaWave null-testing audio comparator (beta)

[esldude]

3 hours ago, pkane2001 said:

 

Can you try the same test with different music track? And sorry, I missed it, but what was different between these two captures? DAC only or DAC and ADC?

I'm sorry I left out part of the info I intended to include in the last post.  In the prior post I had loopback results vs the original file for the Zen Tour loopback, and the same with external clocking plus one with a separate DAC feeding the Zen Tour.  The corrected drift had a consistent pattern in all of those.  

 

In my most recent post the first one is loopback results for a Focusrite Forte and loopback for a Focusrite 18i20.  So everything was different.  The scale of the corrected drift differed, but had the same pattern in it. 

 

Also in the post with all the drift graphs the last two were with a completely different track of music.  Time of that track was nearly the same at just over a minute.  With the other track the pattern of corrected drift was a different pattern.  Though I only showed two of them like the other that pattern remains under several conditions and even using different DACs with different total drift. 

 

Which looks like the content of the file tested has a unique pattern that shows up in the corrected drift curve even with different gear.  Which seems like the content of the file is effecting DW results.  Then again, maybe there is something I don't understand.   I'll post the results for a third piece of music in a few minutes. 

[esldude]

44 minutes ago, Arpiben said:

I have been out and busy those last days but should have more time left for a few tests.

@esldude Dealing with your last tests and queries keep in mind that DW only correct linear drifts in time domain .

In other words it is correcting only Frequency Offsets (steady) in Frequency Domain.

Clocks have frequency offset, frequency aging, frequency accuracy, etc....

A linear frequency drift ( Frequency Domain) is a parabolic curve in time domain.

 

Forgetting temperature, warming time (30min), DC fluctuations, vibrations, etc, when you compare two clocks or sampled signals based on them you need to take into account the linear frequency drift ( clock aging) or differential one ( 2 clocks ) especially when comparing signals recorded with big time lapse ( day(s), month).

Hope it helps.

Rgds.

But I am seeing that pattern in results several days apart, less than two minutes apart, with completely different gear.  All the gear in these tests have been on for several hours.  Some of the external clocks applied were on just a few minutes.  

[esldude]

Third piece of music.  First a loopback measure on the Zen Tour interface, and then a separate DAC feeding the ZT ADC.  A pattern consistent across conditions with this piece of music.  But a third pattern with the third piece of music.  These two are not quite identical, but almost. 

 

[esldude]

27 minutes ago, pkane2001 said:

 

It would be interesting if the content somehow has an effect on clock drift. Can't think of any mechanism that could cause that, inside DeltaWave or in the physical world.

I cannot think of anything either.

 

I also have noticed I can slice off either end, and get the same pattern minus the part sliced off. 

[esldude]

Just now, pkane2001 said:

 

I'd be curious to take a look at a couple original/loopback tracks using the same content, exhibiting the same residual drift. Would it be possible for you to share them?

 

Yes, it might be later.  Uploads on my pitiful internet are iffy this time of day.  

[esldude]

https://www.dropbox.com/s/jrmx9khrajsxmpp/guy.7z?dl=0

 

https://www.dropbox.com/s/hp9wlnpbkxo35tc/Caram.7z?dl=0

 

https://www.dropbox.com/s/xwu8dlx9ujtnn3l/Fleck.7z?dl=0

 

Three different bits of music.  Each one has the original, a loopbacked copy and a copy with separate DAC and ADC.  Each bit of music will leave a very similar drift plot in the two copies.  Each bit of music has a different pattern in that plot that seems to follow the music and not the device, clocks used etc. 

[esldude]

6 minutes ago, blue2 said:

What about using a different computer to play the music?

Actually some of these were done that way.  Some were with a Win10 machine and some with a Macbook pro.  The loopbacks on the Zen Tour were done both ways.  Those several days apart were first Mac and then later Win.  

[esldude]

10 hours ago, Jud said:

 

Or - oh dear! 👹 - the clocking done with the recording somehow comes through in the results! 😳

I don't think that is what is happening.  But I have a way to check it out actually.  I'll see what it looks like. If clocking in the original recording is getting thru to the 1st generation copy, then I should see the same result comparing 1st and 2nd generations.   My guess is the software has some relation to the file effecting how well it lines up, but even that doesn't seem likely.  I'd like to know what is going on however. 

 

EDIT:OK the pattern of drift and the magnitude of it does get thru each subsequent generation.  All the way up to the 8th generation.  I don't suppose that says clocking of the recording is getting thru.  It could be an interaction of the recording clock and the file data.  And I don't know what the original clocking drift is.  It is rather interesting and I don't know how that could happen unless the sample values interact with the alignment algorithms in some way.  I don't know enough about it beyond that to be of much help. 

 

I don't think it is clocking actually because previously I've changed clocks and three of them give the same pattern on one of my ADCs.  I feel sure all three clocks aren't drifting in the same pattern.  So something else is going on.  Also in these 8th gen files I had a separate DAC feeding my ADC so the two clocks aren't going to always synch up the same way or drift from the same starting point 8 times in a row.  

[esldude]

Ok using Bob Marley in this case.  Starts with original vs 1st generation, and finishes with 7th gen vs 8th generation.  The pattern isn't identical, but the basic pattern of drift makes it all the way through them all.  March DAC feeding Zen Tour ADC. 

 

[esldude]

Here is original Phil Woods vs 1st gen followed by 7th gen vs 8th gen.  March DAC feeding Zen Tour ADC.

 

[esldude]

Did some more loopbacks.  Using the Zen Tour with its own clock.  One set with a Macbook over Thunderbolt.  One set with a Lenovo over USB.   The same patterns emerged.  Mac first and Lenovo 2nd.  Both of my test music files produced the patterns already seen. 

 

 

 

[esldude]

2 hours ago, pkane2001 said:

 

Here's another test. If the data was causing the very unique drift pattern, then it shouldn't matter how the drift was generated. This seems to be confirmed by the different loop-back equipment producing a similar pattern in your tests.

 

What if we try to add the same amount of drift in Audacity, using @fas42' s method? If the content of the file is causing the problem, then the same residual drift pattern should be detected there. 

 

Here's Bob Marley fourth generation compared to the original. The recognizable pattern in the residual drift is there, drift measured at 2.41ppm:

 

Now, let's do the same with the artificially induced drift in Audacity, applied on top of the the original file (same scale as above), drift of 2.83ppm:

 

And now, the same but zoomed in a bit further. No similar pattern is detectable now:

 

So, if not passed through the loop-back mechanism, it appears that the distinctive drift pattern doesn't show.

 

This doesn't prove that the content is not at fault here, but it does give some evidence against it.

 

EDIT: As another test, I added artificial 2.83ppm drift to the 4th generation wav file. Then compared that to the original. Same exact pattern remains, undisturbed. DW also computed the drift correctly (2.83 + original 2.41 = 5.24ppm):

You are forgetting I see the patterns when using the March DAC feeding the Zen Tour without any loopback in use. 

 

A bit more curious were these results.  First the Zen Tour connected to the USB Windows machine playing into the 18i20 ADC which is USB connected to the Macbook.  The drift magnitude is about 5 times larger, but the same pattern.  This is the Anna Caram track. 

 

 

Here is a Focusrite Forte playing into the 18i20 ADC.  Lower drift magnitude than above, but higher than loopbacks.  Yet pretty much the same pattern again. 

 

 

March Dac playing into the 18i20 ADC.

[esldude]

1 minute ago, pkane2001 said:

 

Yes, and that's why I'd like to know the source configuration. I don't suspect the loopback equipment is causing this, but it is possible that the source software/PC/cable/converter/resampler/OS/DSP might be.

 

If the content of the original file with added drift is causing this, then we should see the same pattern when comparing original to Audacity-induced drift version. That isn't happening, so it is likely something else.

I was just about to ask about this.  I had already done it the other way.  I added 10 ppm drift to the original file.  Compared it and the pattern remains.  So we did something different.  Here is the original 10 ppm fast vs the capture of the March playing into the 18i20.

 

[esldude]

4 minutes ago, pkane2001 said:

 

Yes, and that's why I'd like to know the source configuration. I don't suspect the loopback equipment is causing this, but it is possible that the source software/PC/cable/converter/resampler/OS/DSP might be.

 

If the content of the original file with added drift is causing this, then we should see the same pattern when comparing original to Audacity-induced drift version. That isn't happening, so it is likely something else.

I'm at a loss as to what else you want to know.  I've done this with different laptops, ADC, DAC, clocking etc.  

 

The Zen Tour captures of other DACs, were my Win 10 Lenovo playing the track via Foobar ASIO with all the DACs USB connected.  The Zen Tour was Thunderbolt connected via Macbook Pro.  I've recorded with Audacity on the Mac.  I did a couple with Reaper on the Mac with no difference.  I also used Reaper to play a couple on the Win10 machine with no difference. 

[esldude]

3 minutes ago, pkane2001 said:

 

Looks like 80ppm drift? How did you add it?

 

The compare file in both cases was from an 18i20 capture of a March DAC.  70.89 vs the original, and 80.89 vs the original sped up 10 ppm in Audacity.

 

So did you use the original as Ref, and 10 ppm fast as Compare?

[esldude]

22 minutes ago, pkane2001 said:

 

Just trying to understand. So you took a file captured over loop-back, then added 10ppm drift to it? I tried that too, and the pattern remained unchanged after drift addition.

 

Did you also try to add drift to the original file and see if the pattern is visible in such a comparison? That's one of the tests  I did above.

I played the file over the March DAC.  Its output captured by the 18i20 ADC. 

I used this for the compare file in both cases. 

 

First I compared to the original file. 

Second compared to the original file sped up 10 ppm. 

 

The compare file capture was unchanged in both cases. 

 

I agree that if the content modulated the software during alignment you'd expect the original vs the original sped up to show the same pattern and it does not.  I did also do that test myself. Still leaves me wondering where the pattern is coming from. 

[esldude]

8 minutes ago, pkane2001 said:

 

We must be doing something different. I took your Caram A M ZT44 file, compared it to the original. The same pattern as you're seeing:

 

Then, took the same file, sped it up around 10ppm in Audacity, and compared them. None of the same pattern is visible:

Yes I agree.  When I compare a file to itself sped up the pattern is not there.  

[esldude]

3 minutes ago, pkane2001 said:

 

Then it's not clock drift that's causing it, and it's not file contents. The question remains, what?

I assume the upper frequencies are not in phase in a capture vs an original.  Could that be resulting in the corrected drift pattern in combination with file content?  Remember in the 18i20 and Forte captures the pattern was there, but the amplitude of the pattern was different (larger).  I know the Forte has a mimimum phase filter with mostly post ringing rather than a more conventional filter. 

[esldude]

Wasted enough time on this for now.  I can see if it is still there in the next version where I believe you said you were improving precision.  Just puts a bee in my bonnet to see that pattern over so many changes, and not know how it gets there. 

[esldude]

Don't know why I didn't think of this earlier.  I was always using the left channel.  So if content interacts with the software the right channel should not have the same pattern.  When I tried that the same pattern is there in the various configurations in the right channel as well.  Plus with L+R.  

 

I did notice another curiosity.  Using the Anna Caram track the left always shows .01 ppm more drift.  With separate DACs and ADCs it was true, with external clocking and with loopbacks with a common clock it was true.  You might get .85 ppm for the left and you get .84 ppm for the right channel.  Loopbacks you get .01 ppm on the left and 0 ppm on the right.  BTW I was very surprised to see .01 ppm on loopbacks when I first did them last week.  You should be seeing 0 ppm on those.   The other test track I've been using shows the same on both channels and 0 ppm on loopbacks. 

[esldude]

13 minutes ago, pkane2001 said:

 

Dennis, you were on to something when you thought of phase. Except it’s the phase of the lower frequencies that is the problem here, not the higher ones. High pass filter of 800Hz or so eliminates the pattern completely. Needs to be applied in Audacity since DW applies filters at the end of processing, and not at the beginning.

 

What causes these errors remains to be determined, but we are getting closer! 

I was about to ask about that.  As I tried cutting frequencies at both ends, and came to the conclusion the filtering must be done after alignment.  Now I know this might complicate matters, do you think having an option to filter prior to alignment might be worthwhile.  Or maybe that filtering prior to alignment when filtering is selected is simply a better way to go about it?

[esldude]

Another pointer to it somehow being in the recorded file properties,  I used the original file with the Anna Caram snippet twice.   And looked at that versus a loopback.  You see the pattern repeat.  Notice the lower point occurs at 34 seconds in the single file.  The single file was 1:07.  Add 34 seconds and you'd expect it to happen again at 1:41.  Which it does. 

[esldude]

3 hours ago, pkane2001 said:

 

Dennis, you were on to something when you thought of phase. Except it’s the phase of the lower frequencies that is the problem here, not the higher ones. High pass filter of 800Hz or so eliminates the pattern completely. Needs to be applied in Audacity since DW applies filters at the end of processing, and not at the beginning.

 

What causes these errors remains to be determined, but we are getting closer! 

I don't know definitively, but am pretty sure none of my interfaces are direct coupled.  So they likely go thru a cap.  They likely roll a bit early as in recordings low frequency garbage is a problem.  So they might have some phase anomalies an octave or three above where they start getting close to flat response.   So the next question would be how does this interact with the software or otherwise to cause a genuine drift pattern.  Is it a residual of what Deltawave does, or is it a real drift difference actually happening in the signal itself?

[esldude]

I just checked the Zen Tour and was surprised to find it is fully flat down to 10 hz and only .8 db down at 2 hz.  

[esldude]

The 18i20 is only flat down to 300 hz.  The drop is very slow reaching -1 db at 20 hz, but then 18 db down at 2 hz.  Maybe if the roll off is effecting phase that is why the pattern was at a higher magnitude when it was involved.