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Evaluating AD/DA loops by means of Audio Diffmaker
Old 1 week ago | Show parent
  #2401
Gear Head
 
Quote:
Originally Posted by didier.brest ➡️
What is the AD filter setting of the ADI-2: slow, sharp, SD slow, SD sharp?



293 ns, 0.1987 dB (L), 0.1788 dB (R), -66.5546 dBFS (L), -67.8840 dBFS (R)

Nice result but will not be registered in the list of the results because it does not fulfil the condition that the sampling rate at DA input and AD output of the converter shall be 44.1 kHz:


Loopback tests requested by forum members: Eventide H8000FW and H9000R (for confirming the ones at the top of the list of the results), Pacific Microsonics Model One and Model Two, Slate Digital VRS-8, SSL 2+, RME M-32 AD Pro --> M-32 DA Pro, RME M-1610 Pro, Audient iD14 MKII, Prism Dream DA-2 --> AD-2, BlackLion Audio Revolution 2×2, RME MADIface Pro. Of course any other one welcome!
Filter was SD Sharp for both files.
Old 1 week ago | Show parent
  #2402
Here for the gear
 
Quote:
Originally Posted by pkane ➡️
Filter was SD Sharp for both files.
(352k->44) is more accurate because of the lower phase degradation near Nyquist frequency 22050Hz (see attachment). The reason is pretty obvious. In case of 352k sample rate the drawbacks of the anti aliasing filter are far above the 22k and are effectively filtered out by properly implemented down-sampling.
Attached Thumbnails
Evaluating AD/DA loops by means of Audio Diffmaker-352vs44.png  
Old 1 week ago | Show parent
  #2403
Gear Head
 
Quote:
Originally Posted by [email protected] ➡️
(352k->44) is more accurate because of the lower phase degradation near Nyquist frequency 22050Hz (see attachment).
Hi Serge,

Yes, the filter is what caused the difference. This is what I said earlier in the thread, and wanted to illustrate with an example. The important thing to realize here is that it's not always the hardware that causes the difference, and that this difference is very likely inaudible.

The phase difference is easier to see in a phase plot. Here are the same two files measured with DeltaWave.
Attached Thumbnails
Evaluating AD/DA loops by means of Audio Diffmaker-352_8.jpg   Evaluating AD/DA loops by means of Audio Diffmaker-44_1.jpg  
Old 1 week ago | Show parent
  #2404
Here for the gear
 
Quote:
Originally Posted by pkane ➡️
Hi Serge,

Yes, the filter is what caused the difference. This is what I said earlier in the thread, and wanted to illustrate with an example. The important thing to realize here is that it's not always the hardware that causes the difference, and that this difference is very likely inaudible.

The phase difference is easier to see in a phase plot. Here are the same two files measured with DeltaWave.
That's interesting, and makes total sense. I imagine one doesn't have to go near as high as 352k to get similar results--perhaps a mere 96.
Old 1 week ago | Show parent
  #2405
Gear Head
 
Quote:
Originally Posted by FreeJazzClub ➡️
That's interesting, and makes total sense. I imagine one doesn't have to go near as high as 352k to get similar results--perhaps a mere 96.
That depends on the filter implementation. Testing with the same Element 24 to ADI-2 Pro FS configuration, but now at 88.2k, the RMS difference result is not nearly as good as at 352.8k, but a bit better than at 44.1k:

(AD @ 88.2k): -55.04 dBFS (L), -56.31 dBFS (R)

Phase plot attached.
Attached Thumbnails
Evaluating AD/DA loops by means of Audio Diffmaker-88.2.jpg  
Old 1 week ago | Show parent
  #2406
Lives for gear
 
esldude's Avatar
 
🎧 5 years
Quote:
Originally Posted by pkane ➡️
Thank you, Didier! This matches my result for the first file.

The second file was recorded at 352.8kHz by the same AD. DA was unchanged, and the file down-sampled to 44.1k. What I find interesting is that the AD sampling rate change caused a significant change in the RMS difference:

File 1: -49.57 dBFS (L), -50.53 dBFS (R)
File 2: -66.55 dBFS (L), -67.84 dBFS (R)
I have been experimenting with the same thing last week. I didn't put in any results because it sort of seemed like cheating vs other results posted.

I achieved similar results simply engaging Phase EQ in Deltawave.

In this case a Topping D10 balanced feeding an RME Babyface Pro FS went from -45.02 db to -60.95 db with Phase EQ engaged in Deltawave. Engaging Level EQ along with Phase EQ only increased it to -61.01 db. Doing this is simpler than messing with sample rates. Thanks to how well Pkane's software works.

Last edited by esldude; 1 week ago at 07:53 AM..
Old 1 week ago | Show parent
  #2407
Lives for gear
 
🎧 10 years
Quote:
Originally Posted by esldude ➡️
I had been experimenting with the same thing last week. I didn't put in any results because it sort of seemed like cheating vs other results posted.

I might need to look back, but I think I achieved similar results in Deltawave with phase EQ engaged without the oversampling followed by downsampling.
It's not cheating, this thread has nothing but an established convention that only exists for the thread..

... but people reading it likely want to know how to achieve the most transparent loop-back for outboard gear.

The high sample rate results show that high sample rates are the better way to achieve it.

Sadly, that then makes the results at 44.1Khz unhelpful and all a little bit of a waste of time other than just wanting to know the 44.1khz result for the sake of it.
Old 1 week ago
  #2408
Lives for gear
 
esldude's Avatar
 
🎧 5 years
I fear most of the results in the long list are mostly just a list of how much the phase in the upper octaves diminish the null value. The good thing is the files are available and Deltawave could correct for the phase giving a clearer picture of what devices are more accurate in the other ways.

I hope Paul doesn't mind me linking to the list he has here:
https://deltaw.org/gearslutz.html#
Old 1 week ago | Show parent
  #2409
Here for the gear
 
Quote:
Originally Posted by pkane ➡️
Hi Serge,

Yes, the filter is what caused the difference. This is what I said earlier in the thread, and wanted to illustrate with an example. The important thing to realize here is that it's not always the hardware that causes the difference, and that this difference is very likely inaudible.

The phase difference is easier to see in a phase plot. Here are the same two files measured with DeltaWave.
Hi Paul,

The diffrograms I provided are phase ones, the magnitude degradation is less dramatic; both ones are not equal across the test sample (attached).

The audibility of phase degradation is a complicated issue, so I don't even want to start the discussion here )).

I know didier.brest does not like when the thread is overloaded with side discussions - maybe he/we will start accompanying separate thread for them. Does this have sense?
Attached Thumbnails
Evaluating AD/DA loops by means of Audio Diffmaker-352vs44_full.png  
Old 1 week ago | Show parent
  #2410
Gear Head
 
Quote:
Originally Posted by esldude ➡️
I have been experimenting with the same thing last week. I didn't put in any results because it sort of seemed like cheating vs other results posted.

I achieved similar results simply engaging Phase EQ in Deltawave.

In this case a Topping D10 balanced feeding an RME Babyface Pro FS went from -45.02 db to -60.95 db with Phase EQ engaged in Deltawave. Engaging Level EQ along with Phase EQ only increased it to -61.01 db. Doing this is simpler than messing with sample rates. Thanks to how well Pkane's software works.
Hi Dennis,

Yes, I'd say using DeltaWave phase correction function is more like cheating because it linearizes phase response of the loopback capture after it's been captured, in other words, correcting for the error introduced by the hardware.

On the other hand, what I captured at 352k was not processed by anything other than the loopback hardware itself.

If I take the loopback result for Element 24 -> ADI Pro FS at 44.1k, the original result, as reported by Didier is:

File 1: -49.57 dBFS (L), -50.53 dBFS (R)

If I use the same file with phase correction in DW, the result is very different, and even better than what was produced by the 352k AD capture:

(AD @44.1k + DW phase eq): -80.27 dBFS (L), -80.61 dBFS (R)

This is because DW corrects for even the tiniest phase errors. Phase plot attached (white line is after the DW correction, blue -- before). Note that I zoomed in quite a bit compared to the previous phase plots to show just how linear the phase can be with proper correction.
Attached Thumbnails
Evaluating AD/DA loops by means of Audio Diffmaker-44k-dw.jpg  
Old 1 week ago | Show parent
  #2411
Gear Head
 
Quote:
Originally Posted by [email protected] ➡️
Hi Paul,

The diffrograms I provided are phase ones, the magnitude degradation is less dramatic; both ones are not equal across the test sample (attached).

The audibility of phase degradation is a complicated issue, so I don't even want to start the discussion here )).

I know didier.brest does not like when the thread is overloaded with side discussions - maybe he/we will start accompanying separate thread for them. Does this have sense?
Hi Serge,

Aha! I didn't realize you were posting phase diffograms.
Sure, let's start another thread if you want to continue the conversation.
Old 6 days ago | Show parent
  #2412
Here for the gear
 
Quote:
Originally Posted by nat8808 ➡️
It's not cheating, this thread has nothing but an established convention that only exists for the thread..

... but people reading it likely want to know how to achieve the most transparent loop-back for outboard gear.

The high sample rate results show that high sample rates are the better way to achieve it.

Sadly, that then makes the results at 44.1Khz unhelpful and all a little bit of a waste of time other than just wanting to know the 44.1khz result for the sake of it.
I don't think it's unhelpful, it provides a baseline if the higher sample rate is truly going to be better every time. In any case, not all differences are audible, especially as we get lower and lower, so 44.1 will suit a lot of people.
Old 6 days ago | Show parent
  #2413
Lives for gear
 
esldude's Avatar
 
🎧 5 years
Quote:
Originally Posted by pkane ➡️
Hi Dennis,

Yes, I'd say using DeltaWave phase correction function is more like cheating because it linearizes phase response of the loopback capture after it's been captured, in other words, correcting for the error introduced by the hardware.

On the other hand, what I captured at 352k was not processed by anything other than the loopback hardware itself.

If I take the loopback result for Element 24 -> ADI Pro FS at 44.1k, the original result, as reported by Didier is:

File 1: -49.57 dBFS (L), -50.53 dBFS (R)

If I use the same file with phase correction in DW, the result is very different, and even better than what was produced by the 352k AD capture:

(AD @44.1k + DW phase eq): -80.27 dBFS (L), -80.61 dBFS (R)

This is because DW corrects for even the tiniest phase errors. Phase plot attached (white line is after the DW correction, blue -- before). Note that I zoomed in quite a bit compared to the previous phase plots to show just how linear the phase can be with proper correction.
I would think this would improve closer to the full DW corrected value if you upsampled the original file to 352 khz and played it at 352 khz as well as capturing it at 352 khz on the AD side. I think both methods are "cheating" in terms of what Didier wants in this thread. Not that such experimenting isn't interesting.
Old 6 days ago | Show parent
  #2414
Gear Head
 
Quote:
Originally Posted by esldude ➡️
I would think this would improve closer to the full DW corrected value if you upsampled the original file to 352 khz and played it at 352 khz as well as capturing it at 352 khz on the AD side. I think both methods are "cheating" in terms of what Didier wants in this thread. Not that such experimenting isn't interesting.
I’d try it, but the Apogee interface only goes up 192k.
Old 6 days ago | Show parent
  #2415
Lives for gear
 
🎧 10 years
Quote:
Originally Posted by FreeJazzClub ➡️
I don't think it's unhelpful, it provides a baseline if the higher sample rate is truly going to be better every time. In any case, not all differences are audible, especially as we get lower and lower, so 44.1 will suit a lot of people.
I guess what I was saying was that the magnitude of difference between different ADDA loops at 44.1khz is much less than the using the same equipment ay a higher sample rate (depending on the filters used in thae gear)..

If folks were using the thread to potentially buy new gear, they may well be better off just using what they already have but in a different way.
Old 6 days ago | Show parent
  #2416
Here for the gear
 
Quote:
Originally Posted by nat8808 ➡️
I guess what I was saying was that the magnitude of difference between different ADDA loops at 44.1khz is much less than the using the same equipment ay a higher sample rate (depending on the filters used in thae gear)..

If folks were using the thread to potentially buy new gear, they may well be better off just using what they already have but in a different way.
Oh yeah I like that take.
Old 4 days ago | Show parent
  #2417
Lives for gear
 
funka's Avatar
 
🎧 15 years
Hi Didier,

Here are two new loops with Focusrite Blue DA 260 as DAC and Blue AD 245(serial 53) as ADC, set @ 20dB u sensitivity, master clock:
- AD 245 master with WC
- AD 245 master with AES

In both tests, Aurora 16 had its synchro lock off.

I wonder if the Blue DA 260 is on par with AD 245...and how it compares to other tests already done with SPL Madison & Forssell MDAC-4...?

My first listening tests told me that the level of detail was quite great.
Old 4 days ago | Show parent
  #2418
Lives for gear
 
didier.brest's Avatar
 
🎧 10 years
Quote:
Originally Posted by funka ➡️
Here are two new loops with Focusrite Blue DA 260 as DAC and Blue AD 245(serial 53) as ADC
Hi Guillaume,

Good results but both the Forsell MDAC-4 and the SPL Madison performed better than the Focusrite Blue DA 260 as DA converter in combination with the Blue AD 245:
Quote:
Originally Posted by funka ➡️
36.020 µs, 1.9698 dB (L), 1.9986 dB (R), -71.4014 dBFS (L), -71.4014 dBFS (R)

Quote:
Originally Posted by funka ➡️
39.288 µs, 1.9788 dB (L), 2.0083 dB (R), -71.4346 dBFS (L), -71.4358 dBFS (R)

To be added to the next issue of the

Loopback tests requested by forum members: Eventide H8000FW and H9000R (for confirming the ones at the top of the list of the results), Pacific Microsonics Model One and Model Two, Slate Digital VRS-8, SSL 2+, RME M-32 AD Pro --> M-32 DA Pro, RME M-1610 Pro, Audient iD14 MKII, Prism Dream DA-2 --> AD-2, BlackLion Audio Revolution 2×2, RME MADIface Pro. Of course any other one welcome!

Last edited by didier.brest; 4 days ago at 03:33 PM..
Old 4 days ago | Show parent
  #2419
Lives for gear
 
funka's Avatar
 
🎧 15 years
Ok, cool, not bad.
I imagine there was also DC offsets (coming from DC coupled AD 245...), but I have no idea of the design of the DAC.
Do you always compensate for DC offsets in matlab computations?
Old 4 days ago | Show parent
  #2420
Lives for gear
 
didier.brest's Avatar
 
🎧 10 years
Quote:
Originally Posted by funka ➡️
Do you always compensate for DC offsets in matlab computations?
Yes:
Quote:
Originally Posted by didier.brest ➡️
RMS level measurement is done after removal of the first and last 1000 samples and the DC offset.
Old 4 days ago | Show parent
  #2421
Lives for gear
 
funka's Avatar
 
🎧 15 years
Ok, thanks Didier for the reminder.
Old 5 hours ago | Show parent
  #2422
Here for the gear
 
Quote:
Originally Posted by pkane ➡️
Sure, let's start another thread if you want to continue the conversation.
If it's only two of us then the new thread is hardly necessary, we can talk any place including PM.
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