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Evaluating AD/DA loops by means of Audio Diffmaker
Old 31st January 2013
  #211
Deleted 6ccb844
Guest
I ran a full jitter clock test for spectral density, frequency spectrum analyser and THD / Noise / Anomalies Test on the 828 MK2..

I'm not sure why diffmaker thinks of it so highly..

I was thinking about taking the Apogee Symphony into the shop, but the thought of voiding the warranty and taking it apart seemed like too much
Old 3rd February 2013
  #212
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didier.brest's Avatar
 

I started to include some download links. The two first figures before the correlated null depth (Corr Depth) ones are the gain correction to be applied to the loopback copy for retrieving the level of the original. I will edit this post later on for providing the links and the gain correction figures for all the loopback files.

DA-AD loops from this wav file evaluated by means of Audio DiffMaker.

ADDA converters

Lynx Hilo (CoolColJ)

-0,1 dB (L), -0,1 dB (R) Corr Depth: 41,8 dB (L), 43,7 dB (R), Difference: -56,8 dBFS (L), -57,2 dBFS (R)

MOTU 2408mk3 (ram75)
0,1 dB (L), 0,1 dB (R) Corr Depth: 36,3 dB (L), 37,9 dB (R) Difference: -55,80 dBFS (L), -56,9 dBFS (R)

MOTU 24I/O (ram75)
0,1 dB (L), 0,1 dB (R) Corr Depth: 36,3 dB (L), 37,9 dB (R) Difference: -55,80 dBFS (L), -56,8 dBFS (R)

MOTU 828mk2 (laurend)
6,1 dB (L), 6,2 dB (R) Corr Depth: 36,4 dB (L), 37,9 dB (R) Difference: -55.7 dBFS (L) -57.0 dBFS (R)

Mytek 8 x 192 (MainTime)
0,4 dB (L), 0,5 dB (R) Corr Depth: 35,3 dB (L), 36,9 dB (R) Difference: -55.2 dBFS (L) -56.0 dBFS (R)

Aurora 8 (cylens)
-0,085dB (L), -0,080dB (R) Corr Depth: 34,6 dB (L), 36,3 dB (R) Difference: -54.2 dBFS (L) -55.1 dBFS (R)

TC Electronics Impact Twin (AndG)

-0,432dB (L), 0,029dB (R) Corr Depth: 32,0 dB (L), 33,6 dB (R) Difference: -51.7 dBFS (L) -52.7 dBFS (R)

RME HDSP 9632 (schtim)
0,5 dB (L), 0,5 dB (R) Corr Depth: 31.4 dB (L), 33.0 dB (R) Difference: -51.2 dBFS (L) -52.1 dBFS (R)

Prism Orpheus (MainTime)
0,1 dB (L), 0,1 dB (R) Corr Depth: 30,8 dB (L), 32,4 dB (R) Difference: -51.1 dBFS (L) -52.4 dBFS (R)

RME Fireface 400 (didier.brest)
0,3 dB (L), 0,3 dB (R) Corr Depth: 30,2 dB (L), 31,8 dB (R) Difference: -49.8 dBFS (L) -50.8 dBFS (R)

TC Electronics Impact Twin (ben)
Corr Depth: 29,1 dB (L), 30,8 dB (R) Difference: -48,7 dBFS (L), -49,7 dBFS (R)

Echo Audiofire 12 (guze)
Corr Depth: 28,8 dB (L), 30,1 dB (R) Difference: -48.4 dBFS (L) -49.2 dBFS (R)

E-MU 1616m (left channel only, ben)
Corr Depth: 28,9 dB (L) Difference: -45,9 dBFS (L)

Apogee Symphony I/O (Ajantis)
Corr Depth: 43,4 dB (L), 45,6 dB (R) Difference: -45,9 dBFS (L), 45,5 dBFS dB (R)

Echo Audiofire 4 (david1103)
Corr Depth: 25,6 dB (L), 27,4 dB (R) Difference: -45,2 dBFS (L), -46,3 dBFS (R)

Metric Halo ULN-2 (DownSideUp)
Corr Depth: 25,3 dB (L), 26,9 dB (R) Difference: -44,9 dB (L), 46,0 dB (R)


Echo Audiofire 8 non adat CS4272 (guze)

0,8 dB (L), 0,9 dB (R) Corr Depth: 26,4 dB (L), 28,2 dB (R) Difference: -40.6 dBFS (L) -40.6 dBFS (R)

RME Multiface II - Unbalanced, -10 dBV (juki, Audiofanzine)
Corr Depth: 22,7 dB (L), 24,4 dB (R) Difference: -42,4 dBFS (L) -43,5 dBFS (R)

RME Fireface 800 (genelec79)
Corr Depth: 22,3 dB (L), 23,9 dB (R) Difference: -41,9 dB (L), -43,0 dB (R)

RME Multiface II - Balanced, 4 dBu (juki, Audiofanzine)
Corr Depth: 22,3 dB (L), 23,9 dB (R) Difference: -41,9 dBFS (L) -43,0 dBFS (R)

Apogee Duet2 (isma)
1,0 dB (L), 0,9 dB (R) Corr Depth: 19,8 dB (L), 21,4 dB (R) Difference: -40.2 dBFS (L) -41.6 dBFS (R)

Focusrite Saffire Pro 24 DSP (CoolColJ), first 45s part disregarded
5,2 dB (L), 5,2 dB (R) Corr Depth: 20,2 dB (L), 22,0 dB (R) Difference: -38,9 dBFS (L), -39,9 dBFS (R)

RME Fireface UFX, XLR outputs 1-2 to TRS inputs 3-4 (didier.brest)
0,8 dB (L), 0,7 dB (R) Corr Depth: 18,5 dB (L), 20,1 dB (R) Difference: -38,9 dBFS (L), -40,3 dBFS (R)

RME Fireface UFX, TRS outputs 5-6 to TRS inputs 3-4 (didier.brest)
0,7 dB (L), 0,7 dB (R) Corr Depth: 18,4 dB (L), 20,1 dB (R) Difference: -38,8 dBFS (L), -40,3 dBFS (R)

Yamaha Steinberg MR816X (didier.brest)
1,1 dB (L), 0,6 dB (R) Corr Depth: 19,1 dB (L), 21,0 dB (R) Difference: -38.6 dBFS (L) -40.0 dBFS (R)

RME Fireface UFX, XLR outputs 1-2 to XLR preamp inputs 9-10 (didier.brest)
0,5 dB (L), 0,4 dB (R) Corr Depth: 14,7 dB (L), 16,2 dB (R) Difference -35,03 dBFS (L) -36,30 dBFS (R)

Edirol FA-66 (didier.brest)
1,0 dB (L), 0,6 dB (R) Corr Depth: 15,6 dB (L), 17,1 dB (R) Difference: -34.4 dBFS (L) -35.4 dBFS (R)

RME Babyface (didier.brest)
0,6 dB (L), 0,7 dB (R) Corr Depth: 9,2 dB (L), 10,8 dB (R) Difference: -28.8 dBFS (L) -29.8 dBFS (R)


Sets of different converters


Aurora8 clocked by RME HDSPe RayDAT (cylens)
Corr Depth: 34,6 dB (L), 36,3 dB (R) Difference: -55.3 dBFS (L) -56.5 dBFS (R)

Echo Audiofire 8 with ADAT clocked by RME HDSP 9632 (schtim)
Corr Depth: 25.9 dB (L), 27.5 dB (R) Difference: -45.5 dBFS (L) -46.5 dBFS (R)

M-Audio Profire2626 clocked by RME HDSPe RayDAT (cylens)
Corr Depth: 24,4 dB (L), 25,9 dB (R) Difference: -44.1 dBFS (L) -45.0 dBFS (R)

M-Audio Profire2626 clocked by Lynx Aurora8 (cylens)
Corr Depth: 24,4 dB (L), 25,9 dB (R) Difference: -44.0 dBFS (L) -44.9 dBFS (R)

RME Fireface 800 clocked by Yamaha 02R (genelec79)
Corr Depth: 22,3 dB (L), 23,9 dB (R) Difference: -41,9 dBFS (L), -43,0 dBFS (R)

Atoll DAC200 --> RME Babyface (didier.brest)
Corr Depth: 10,1 dB (L), 11,9 dB (R) Difference -30,0 dBFS (L) -31.3 dBFS (R)

RME Babyface --> RME Fireface 400 (didier.brest)
Corr Depth: 16,6 dB (L), 18,4 dB (R) Difference -29,4 dBFS (L), -28,8 dBFS (R)

Benchmark DAC1 phone output ---> Echo Audiofire 4 (david1103)
Corr Depth: 10,4 dB (L), 10,2 dB (R) Difference: -22,6 dBFS (L), -23,1 dBFS (R)

For contributing to this test :
- download the test 2 x 44 kHz x 24 bit wav file (31 Mb),
- cable link the 2 DAC outputs to 2 ADC inputs,
- play back the test file to the DAC outputs and record from the ADC inputs,
- upload to mediafire or any other file sharing site the 2 x 44 kHz x 24 bit wav file from this recording and
- provide the download link here with information about ADC and DAC identities.
Thank you!
Old 3rd February 2013
  #213
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CoolColJ's Avatar
 

Interesting the that the 24 I/O is so close to the 2408 mk3, because I have both and they sound different. 24 I/O is brighter and has less bottom end
2408mk3 sounds closer to my Hilo

In any case I own all 3 of the top 3 listed here :p

I mainly use my two 2408mk3 as extra outputs (via the Hilo ADAT) and it and the 24 i/o as a monitor/digital mixer for my synths, using the PCIe card to hook em all up, feeding into the Hilo ADAT input. The Hilo is the main recording and playback device
Old 3rd February 2013
  #214
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swartzfeger's Avatar
Quote:
Originally Posted by didier.brest View Post
List of results updated with MOTU 2408mk3 and MOTU 24I/O result from ram75 here below.
Didier, thanks for maintaining and archiving this. It's appreciated.

edit -- question regarding the MOTU 2408mk3 and MOTU 24I/O... are those BLA-modded or factory models?

Last edited by swartzfeger; 3rd February 2013 at 10:43 PM.. Reason: question re: MOTU
Old 4th February 2013
  #215
Gear Nut
 

Quote:
Originally Posted by CoolColJ View Post
Interesting the that the 24 I/O is so close to the 2408 mk3, because I have both and they sound different. 24 I/O is brighter and has less bottom end
2408mk3 sounds closer to my Hilo

In any case I own all 3 of the top 3 listed here :p

I mainly use my two 2408mk3 as extra outputs (via the Hilo ADAT) and it and the 24 i/o as a monitor/digital mixer for my synths, using the PCIe card to hook em all up, feeding into the Hilo ADAT input. The Hilo is the main recording and playback device
Exactly my thoughts!, less bottom end.

regarding the 24i/o and the 2408 mk3 (to answer the other question, they're factory made, not BLA modded) they're clocked to an UA 2192 at 48 khz but i can't find the best way to stabilized it, it's always go back and forth to 44khz, my path is: UA BNC out-- 2403 mk3 BNC in with the T adaptor --- 24i/o, something's wrong?

Thank you
Old 4th February 2013
  #216
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didier.brest's Avatar
 

Quote:
Originally Posted by ram75 View Post
Exactly my thoughts!, less bottom end.

regarding the 24i/o and the 2408 mk3 (to answer the other question, they're factory made, not BLA modded) they're clocked to an UA 2192
I did not get this information. I have placed your results in the 'Sets of different converters'.
Old 4th February 2013
  #217
Gear Nut
 

Quote:
Originally Posted by didier.brest View Post
I did not get this information. I have placed your results in the 'Sets of different converters'.
Ah ah, not for the test!!!
the test is purely in and out from the motus, no UA involved.
Old 4th February 2013
  #218
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CoolColJ's Avatar
 

Quote:
Originally Posted by ram75 View Post
Exactly my thoughts!, less bottom end.

regarding the 24i/o and the 2408 mk3 (to answer the other question, they're factory made, not BLA modded) they're clocked to an UA 2192 at 48 khz but i can't find the best way to stabilized it, it's always go back and forth to 44khz, my path is: UA BNC out-- 2403 mk3 BNC in with the T adaptor --- 24i/o, something's wrong?

Thank you
I just have the wordclock out from my Hilo to the main 2408mk3.
The PCIe card uses this to clock all the connected devices, 2x2408mk3 and 24i/o

I'm guessing you are using them in stand alone mode?
Old 4th February 2013
  #219
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didier.brest's Avatar
 

Quote:
Originally Posted by ram75 View Post
Ah ah, not for the test!!!
the test is purely in and out from the motus, no UA involved.
OK! Corrected back.
Old 4th February 2013
  #220
Gear Nut
 

Quote:
Originally Posted by CoolColJ View Post
I just have the wordclock out from my Hilo to the main 2408mk3.
The PCIe card uses this to clock all the connected devices, 2x2408mk3 and 24i/o

I'm guessing you are using them in stand alone mode?

Well, i just did that, clocking the 2408 mk3 to the UA and not clocking the 24i/o
and i have the same troubles of désynchronisation 44-48
Old 9th February 2013
  #221
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swartzfeger's Avatar
Anyone do a test on the UA Apollo or Apogee Quartet? Those two are on my radar for possible future purchase.
Old 14th February 2013
  #222
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I recall that in the other loop thread (since deleted) the Apollo was not that impressive and ranked in the lower half of the group.

But if you like the idea of a built-in UAD card, get the Apollo... in this day and age, you won't actually hear the difference between the units that the numbers in the tests suggest.
Old 15th February 2013
  #223
MXX
Gear Nut
 

Yeah, sucks that thread is gone. I would also like to know where the RME Fireface UC and MOTU UltraLite-mk3 Hybrid land at, as I am considering buying one of them (or something better in the same price bracket) and because I cant test myself, it's really down to the specs and feedback...
Old 25th March 2013
  #224
Here for the gear
 

Can anyone share test results for the Antelope Orion 32?
Old 25th March 2013
  #225
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Melgueil's Avatar
 

These tests are interesting to look through, some unexpected results. That said .....

Why anyone would make a purchase decision based on these tests is beyond me.
You are not likely to actually hear any of the differences between the "scores" of these units.

Buy the one that has the features you like and get to work making music.

Cdlt

Last edited by Melgueil; 25th March 2013 at 10:16 PM.. Reason: Spelling
Old 26th March 2013
  #226
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Quote:
Originally Posted by Melgueil View Post
These tests are interesting to look through, some unexpected results. That said .....

Why anyone would make a purchase decision based on these tests is beyond me.
Many believe they served to help dispel converter myths folks on this site hold on to like religion. Particularly useful for budget studios looking for the best bang-for-the-buck performance (feature set aside, of course)

Quote:
You are not likely to actually hear any of the differences between the "scores" of these units. Buy the one that has the features you like and get to work making music.
Agreed.

Anyway, that was a popular thread. Too bad it was mismanaged and deleted; would've driven a lot of traffic to GS. If mods were smart, they would've just locked it.... Keep the traffic while placating any potentially offended sponsors...
Old 26th March 2013
  #227
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didier.brest's Avatar
 

Quote:
Originally Posted by 6strings View Post
Too bad it was mismanaged and deleted
This test was not mismanaged and still alive. I am going to provide download links for most of the DA-AD loops listed herebelow (today done for more than half).

The two first figures before the correlated null depth (Corr Depth) ones are the gain correction to be applied to the loopback copy for retrieving the level of the original. I will edit this post later on for providing the links and the gain correction figures for all the loopback files.

DA-AD loops from this wav file evaluated by means of Audio DiffMaker.

ADDA converters

Lynx Hilo (CoolColJ)

-0,1 dB (L), -0,1 dB (R) Corr Depth: 41,8 dB (L), 43,7 dB (R), Difference: -56,8 dBFS (L), -57,2 dBFS (R)

MOTU 2408mk3 (ram75)
0,1 dB (L), 0,1 dB (R) Corr Depth: 36,3 dB (L), 37,9 dB (R) Difference: -55,80 dBFS (L), -56,9 dBFS (R)

MOTU 24I/O (ram75)
0,1 dB (L), 0,1 dB (R) Corr Depth: 36,3 dB (L), 37,9 dB (R) Difference: -55,80 dBFS (L), -56,8 dBFS (R)

MOTU 828mk2 (laurend)
6,1 dB (L), 6,2 dB (R) Corr Depth: 36,4 dB (L), 37,9 dB (R) Difference: -55.7 dBFS (L) -57.0 dBFS (R)

Mytek 8 x 192 (MainTime)
0,4 dB (L), 0,5 dB (R) Corr Depth: 35,3 dB (L), 36,9 dB (R) Difference: -55.2 dBFS (L) -56.0 dBFS (R)

Aurora 8 (cylens)
-0,085dB (L), -0,080dB (R) Corr Depth: 34,6 dB (L), 36,3 dB (R) Difference: -54.2 dBFS (L) -55.1 dBFS (R)

TC Electronics Impact Twin (AndG)

-0,432dB (L), 0,029dB (R) Corr Depth: 32,0 dB (L), 33,6 dB (R) Difference: -51.7 dBFS (L) -52.7 dBFS (R)

RME HDSP 9632 (schtim)
0,5 dB (L), 0,5 dB (R) Corr Depth: 31.4 dB (L), 33.0 dB (R) Difference: -51.2 dBFS (L) -52.1 dBFS (R)

Prism Orpheus (MainTime)
0,1 dB (L), 0,1 dB (R) Corr Depth: 30,8 dB (L), 32,4 dB (R) Difference: -51.1 dBFS (L) -52.4 dBFS (R)

RME Fireface 400 (didier.brest)
0,3 dB (L), 0,3 dB (R) Corr Depth: 30,2 dB (L), 31,8 dB (R) Difference: -49.8 dBFS (L) -50.8 dBFS (R)

TC Electronics Impact Twin (ben)
Corr Depth: 29,1 dB (L), 30,8 dB (R) Difference: -48,7 dBFS (L), -49,7 dBFS (R)

Echo Audiofire 12 (guze)
0,7 dB (L), 0,7 dB (R) Corr Depth: 28,8 dB (L), 30,1 dB (R) Difference: -48.4 dBFS (L) -49.2 dBFS (R)

E-MU 1616m (left channel only, ben)
Corr Depth: 28,9 dB (L) Difference: -45,9 dBFS (L)

Apogee Symphony I/O (Ajantis)
Corr Depth: 43,4 dB (L), 45,6 dB (R) Difference: -45,9 dBFS (L), 45,5 dBFS dB (R)

Echo Audiofire 4 (david1103)
Corr Depth: 25,6 dB (L), 27,4 dB (R) Difference: -45,2 dBFS (L), -46,3 dBFS (R)

Metric Halo ULN-2 (DownSideUp)
Corr Depth: 25,3 dB (L), 26,9 dB (R) Difference: -44,9 dB (L), 46,0 dB (R)


Echo Audiofire 8 non adat CS4272 (guze)

0,8 dB (L), 0,9 dB (R) Corr Depth: 26,4 dB (L), 28,2 dB (R) Difference: -40.6 dBFS (L) -40.6 dBFS (R)

RME Multiface II - Unbalanced, -10 dBV (juki, Audiofanzine)
Corr Depth: 22,7 dB (L), 24,4 dB (R) Difference: -42,4 dBFS (L) -43,5 dBFS (R)

RME Fireface 800 (genelec79)
Corr Depth: 22,3 dB (L), 23,9 dB (R) Difference: -41,9 dB (L), -43,0 dB (R)

RME Multiface II - Balanced, 4 dBu (juki, Audiofanzine)
Corr Depth: 22,3 dB (L), 23,9 dB (R) Difference: -41,9 dBFS (L) -43,0 dBFS (R)

Apogee Duet2 (isma)
1,0 dB (L), 0,9 dB (R) Corr Depth: 19,8 dB (L), 21,4 dB (R) Difference: -40.2 dBFS (L) -41.6 dBFS (R)

Focusrite Saffire Pro 24 DSP (CoolColJ), first 45s part disregarded
5,2 dB (L), 5,2 dB (R) Corr Depth: 20,2 dB (L), 22,0 dB (R) Difference: -38,9 dBFS (L), -39,9 dBFS (R)

RME Fireface UFX, XLR outputs 1-2 to TRS inputs 3-4 (didier.brest)
0,8 dB (L), 0,7 dB (R) Corr Depth: 18,5 dB (L), 20,1 dB (R) Difference: -38,9 dBFS (L), -40,3 dBFS (R)

RME Fireface UFX, TRS outputs 5-6 to TRS inputs 3-4 (didier.brest)
0,7 dB (L), 0,7 dB (R) Corr Depth: 18,4 dB (L), 20,1 dB (R) Difference: -38,8 dBFS (L), -40,3 dBFS (R)

Yamaha Steinberg MR816X (didier.brest)
1,1 dB (L), 0,6 dB (R) Corr Depth: 19,1 dB (L), 21,0 dB (R) Difference: -38.6 dBFS (L) -40.0 dBFS (R)

RME Fireface UFX, XLR outputs 1-2 to XLR preamp inputs 9-10 (didier.brest)
0,5 dB (L), 0,4 dB (R) Corr Depth: 14,7 dB (L), 16,2 dB (R) Difference -35,03 dBFS (L) -36,30 dBFS (R)

Edirol FA-66 (didier.brest)
1,0 dB (L), 0,6 dB (R) Corr Depth: 15,6 dB (L), 17,1 dB (R) Difference: -34.4 dBFS (L) -35.4 dBFS (R)

RME Babyface (didier.brest)
0,6 dB (L), 0,7 dB (R) Corr Depth: 9,2 dB (L), 10,8 dB (R) Difference: -28.8 dBFS (L) -29.8 dBFS (R)


Sets of different converters


Aurora8 clocked by RME HDSPe RayDAT (cylens)
Corr Depth: 34,6 dB (L), 36,3 dB (R) Difference: -55.3 dBFS (L) -56.5 dBFS (R)

Echo Audiofire 8 with ADAT clocked by RME HDSP 9632 (schtim)
Corr Depth: 25.9 dB (L), 27.5 dB (R) Difference: -45.5 dBFS (L) -46.5 dBFS (R)

M-Audio Profire2626 clocked by RME HDSPe RayDAT (cylens)
Corr Depth: 24,4 dB (L), 25,9 dB (R) Difference: -44.1 dBFS (L) -45.0 dBFS (R)

M-Audio Profire2626 clocked by Lynx Aurora8 (cylens)
Corr Depth: 24,4 dB (L), 25,9 dB (R) Difference: -44.0 dBFS (L) -44.9 dBFS (R)

RME Fireface 800 clocked by Yamaha 02R (genelec79)
Corr Depth: 22,3 dB (L), 23,9 dB (R) Difference: -41,9 dBFS (L), -43,0 dBFS (R)

Atoll DAC200 --> RME Babyface (didier.brest)
Corr Depth: 10,1 dB (L), 11,9 dB (R) Difference -30,0 dBFS (L) -31.3 dBFS (R)

RME Babyface --> RME Fireface 400 (didier.brest)
Corr Depth: 16,6 dB (L), 18,4 dB (R) Difference -29,4 dBFS (L), -28,8 dBFS (R)

Benchmark DAC1 phone output ---> Echo Audiofire 4 (david1103)
5,6 dB (L), 5,8 dB (R) Corr Depth: 10,4 dB (L), 10,2 dB (R) Difference: -22,6 dBFS (L), -23,1 dBFS (R)

For contributing to this test :
- download the test 2 x 44 kHz x 24 bit wav file (31 Mb),
- cable link the 2 DAC outputs to 2 ADC inputs,
- play back the test file to the DAC outputs and record from the ADC inputs,
- upload to mediafire or any other file sharing site the 2 x 44 kHz x 24 bit wav file from this recording and
- provide the download link here with information about ADC and DAC identities.
Thank you!
Old 31st March 2013
  #228
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Quote:
Originally Posted by didier.brest View Post
This test was not mismanaged and still alive.
No, no... I was referring to this other thread (where mods uncharacteristically allowed trolls to freely roam, pillage and burn the highly popular, though controversial thread to the ground).

You're doing great work here. Thanks!

Old 2nd April 2013
  #229
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jinksdingo's Avatar
Glad this thread is still alive and kicking!
Good on you guys!
Old 2nd April 2013
  #230
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swartzfeger's Avatar
Quote:
Originally Posted by jinksdingo View Post
Glad this thread is still alive and kicking!
Good on you guys!
Yes, didier has done a great job with this.

Curious, as popular as the Apollo has been the last year, I've yet to see it appear here (it may've been on the 'old' thread). My Apollo arrives today, so I run it through a loopback to see how it stacks up.
Old 2nd April 2013
  #231
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didier.brest's Avatar
 

Quote:
Originally Posted by swartzfeger View Post
My Apollo arrives today, so I run it through a loopback to see how it stacks up.
I look further to adding the Apollo to the list.
Old 2nd April 2013
  #232
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Hello!

I have been following this discussion, and so far no one has even explained what this program measures. Which is a bit troublesome, as if you don't even know what you are doing, how can you know you are measuring things correctly?

Does the difference of -32db for example mean the program cancels up to 32 db on average after 10 passes? If that's the case I think there is something very wrong with the test, because that just sounds like way too small of a number for the best converter. Perhaps the timing is off or something?

Further, this test is NOT accurate if full bandwidth isn't used, but then there is the issue of LPF on the converter, which might cancel more if it's linear or minimum phase I would think.

I think running a song through a converter gives you very misplaced idea of what is actually happening in any case. Since to me it seems like no one even knows what is being measured here, how can we know if it isn't just the song that's causing the difference? I mean it's pretty logical that some converters might distort at specific frequencies more than some, and if this particular piece contained more of one of those frequencies, you get scewed results! A better test IMO, is to run a sine wave sweep through the converters to map the harmonic distortion and freqency response properly. It's actually nice to know what's being measured as well!

And so far it's interesting that no one here has even posted a frequency response graph. I mean I sure won't care if the frequency response is all messed up at 20hz, which there just might be a huge difference between the converters because AFAIK these converters remove DC offset, which might completely skew these results in the wrong direction! It definitely isn't enough to just know how far the files null. Also if there are errors/weirdness they would most likely pop up in the frequency graph. If two people get way different results, that would tell you something as well.

Putting things through the converters at 0DB is also highly inappropriate! Rembember that meters on the computer actually measure sample values and not real signal peaks. Thus depending on how your DAC handles intersample peaks these would also massively skew the numbers, causing high distortion on some units, but not others, which has nothing to do with the performance of a DAC.

So yeah, it would be nice to actually see THD + frequency response graph of the converters, perhaps even with some dynamics mixed in. I would also be more confident with the results if those were provided. So far I have to say I am a bit sceptical of these results.
Old 2nd April 2013
  #233
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didier.brest's Avatar
 

Quote:
Originally Posted by Oden View Post
Does the difference of -32db for example mean the program cancels up to 32 db on average after 10 passes?
There is only one pass. The difference figures are the RMS level of the L and R channels of the difference between the original and the copy.

Quote:
Originally Posted by Oden View Post
Further, this test is NOT accurate if full bandwidth isn't used.
The difference figures are full band 0-22050 Hz.

Quote:
Originally Posted by =Oden View Post
I think running a song through a converter gives you very misplaced idea of what is actually happening in any case. A better test IMO, is to run a sine wave sweep through it to map the harmonic distortion and freqency response properly.
I don't share your opinion. But if you perform another test according to your recommendations, I will be interested in the results.
Old 2nd April 2013
  #234
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Quote:
Originally Posted by didier.brest View Post
There is only one pass. The difference figures are the RMS level of the L and R channels of the difference between the original and the copy.


The difference figures are full band 0-22050 Hz.


I don't share your opinion. But if you perform another test according to your recommendations, I will be interested in the results.
So... How can you actually know what you are actually measuring with this null test?

Let's take 3 examples.

#1 is completely flat perfect converter, but removes DC offset at 20hz, and has highpass filter at that distorts the phase at 20khz. Further the song is peaking at 0DBFS on right channel, which actually means real peak of 6DB. Those peaks hard clip in the DAC, right and left channel become uncorrelated. The songs won't null even close!

#2 converter doesn't remove DC offset and has a bit skewed frequency response. Still much closer null than 1. This converter has headroom for intersample peaks so no distortion.

#3 converter has perfect frequency response, but has high harmonic distortion when operating at loud level. Result is that, again the files won't null even close.


According to your test what most people would say is the best converter here is actually the worst converter. And the worst is the best. I think that's a bit problematic. Left out from this is the fact that this test treats the issue of THD very poorly.

With simple sine sweep frequency response and THD test, you would actually know what you are getting. Aliasing would show up as well, only IMD would be left out. Far more telling test for sure. THD and aliasing is way more problematic than frequency response related stuff (at least IMO) and this experiment also doesn't take that into account at all. Of course it's a bit hard to measure since THD and aliasing is level dependent.


Further... RMS levels? And how can we know that everyone is using the same RMS size?

Finally, there is just NO WAY that ANY of the converters would null only 6db after being put through one pass of the converter! Thinking about it I have seen many anomalies like this with the experiments that should ring alarm bells. For the record I can put a LPF at 1Khz on one of two same tracks, one phase inverted and it nulls more than that(RMS and peak)! So in your experiments one of the converters is less accurate than a 12db/oct filter at 1000hz on a track. This is if I understand the experiment correctly, which I don't really claim, but so far it seems like no one does!


Edit: I just tested my DC offset hypothesis. Guess what, by removing DC offset at 20hz two completely nulling files nulled only to 6db (to be fair I didn't sample align, but since this is min phase EQ...). I think this is what makes the experiment completely broken. But I can't be sure though. These numbers just have to be incorrect though, there is no way that such small nulls could be produced unless your converters were completely broken!
Old 2nd April 2013
  #235
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didier.brest's Avatar
 

Quote:
Originally Posted by Oden View Post
Further... RMS levels? And how can we know that everyone is using the same RMS size?
I do this measurement myself in Wavelab in the same way for all the loopback files. It is measured on the whole difference, except for a small slice at the beginning where the difference signal is not accurate likely because of the time delay compensation.

Quote:
Originally Posted by Oden View Post
Finally, there is just NO WAY that ANY of the converters would null only 6db after being put through one pass of the converter!
This is the Benchmark DAC1 phone output ---> Echo Audiofire 4 test from david1103. The difference RMS level is -23 dBFS, 6 dB down to the RMS level of the original. I am uploading the file from david1103 so that you can do the measurement yourself. You may not trust the test done by david1103 but you should not claim here that his test is wrong unless you would bring a proof of your claim: get a DAC1 and an Audiofire 4 and do the test yourself.
Old 3rd April 2013
  #237
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Quote:
Originally Posted by didier.brest View Post
I do this measurement myself in Wavelab in the same way for all the loopback files. It is measured on the whole difference, except for a small slice at the beginning where the difference signal is not accurate likely because of the time delay compensation.


This is the Benchmark DAC1 phone output ---> Echo Audiofire 4 test from david1103. The difference RMS level is -23 dBFS, 6 dB down to the RMS level of the original. I am uploading the file from david1103 so that you can do the measurement yourself. You may not trust the test done by david1103 but you should not claim here that his test is wrong unless you would a proof of your claim: get a DAC1 and an Audiofire 4 and do the test yourself.
And how would doing the same test help me in any way? Apart from that I could perhaps use correct gain staging.

But if Benchmark DAC1 -> Echoaudio fire nets you worse results than an LPF at 1Khz on one full range track I tested, don't you find that at all problematic when it comes to validity of your experiment? Can you seriously say that this DAC alters the audio as much as an LP 12db filter at 1Khz? I think absolutely not!

I don't have any of these fancy converters, but I would appreciate it very much if you could run a simple sine wave sweep through yours (At a proper level, that is peaks below -6dbfs). That would very clearly show the DC offset anomalies for example. I think as of now these tests may contain very much mis-information of a quality of the converters in these boxes. I don't think a null test is a very good way to test this and certainly ignores any personal prefrences (such as distortion vs. frequency response) and just doesn't tell anything about how the converter actually changes the signal!
Old 3rd April 2013
  #238
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swartzfeger's Avatar
Quote:
Originally Posted by didier.brest View Post
I look further to adding the Apollo to the list.
The Apollo arrived today and should have it hooked up to my Macbook tomorrow; anyone have any recommendations on how to do a proper loopback using Logic 9?
Old 3rd April 2013
  #239
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didier.brest's Avatar
 

Whatever is your DAW, the process is simple: link two analog outputs to two analog inputs (disable loopback mode that bypass the converters if available like in the RME Fireface), play the original to these analog outputs and simultaneously record from these analog inputs.
Old 3rd April 2013
  #240
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swartzfeger's Avatar
Quote:
Originally Posted by didier.brest View Post
Whatever is your DAW, the process is simple: link two analog outputs to two analog inputs (disable loopback mode that bypass the converters if available like in the RME Fireface), play the original to these analog outputs and simultaneously record from these analog inputs.
Didier, that was what I assumed... I guess my concern was what do I need to be aware of to ensure that both files are the same length, etc.

I know that you occasionally mention some people submit files with errors, and wanted to make sure I avoid the same mistake(s).
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