Topic: Fireface UFX converter - bad quality?

Hi Everyone,

i got a fireface ufx, and i really enjoy it as my recording device! but recently i got very irritated by this thread on gearslutz:

http://www.gearslutz.com/board/gear-sho … hread.html

in this test, which claims to be scientific, the ufx turned out as one of the worst converters... while i cannot believe this, i still would like to ask what that is all about. if anybody can follow the test procedure - please shed some light into this!

i would really appreciate any comments,

Regards,

Fishmac

2

Re: Fireface UFX converter - bad quality?

My first quibble with the testing is that it uses a loop-back method, which means that it's impossible to tell whether the signal degeneration is the result of the input or output analog electronics, and/or the ADC or the DAC. I suppose the argument could be made about "real world use", but when was the last time you routed audio out and back into your interface ten times? Yes, it piles up the degradation, making it easier to hear and measure, but it does little to identify the source of any degradation.

As well meaning as these kinds of tests are, they do seek to provide one standard answer to the nebulous question, "What is the best?" The answer to that will be at best simplistic and reductive. Best for what? Best at what?

I suppose when you are looking to buy one, and only one audio interface, being reductive is part of the purchase decision, but still I would appreciate more detailed results, and more controlled testing. For example, if I were looking to buy an interface where I knew that I'd be using it most for audio capture, rather than playback, then I might be willing to cut some cost corners by getting an interface with stellar analog in and ADC performance, but lesser quality outputs.

Everything in audio is a trade-off. Seeking to find a single, one-size-fits-all answer ignores this fact of life.

Frank Lockwood
https://LockwoodARS.com
Fireface 800, Firmware 2.77
Drivers: Win10, 3.125; Mac, 3.36

3 (edited by panatrope 2012-02-19 00:35:06)

Re: Fireface UFX converter - bad quality?

At the moment, all the tabulated results show is that for the single sample (in most cases) unit of each type tested that there were differences.  Interestingly, the ranking which is shown in terms of Correlation Depth (where a larger number is better) is quite different if the "RMS" level value of the difference file (smaller number is better) is used, where the UFX would be ranked much closer to the top.*   Also the UFX single pass noise figure (not shown for all units) is only bettered by the Lucid unit.

Obviously, the results depend on the processing applied by the test program ("AudioDiff") to determine correlation of the signals, and to what degree this is more reliable than the 'RMS difference level' results.  The program was described in a (I assume peer-reviewed, although it could also have been a poster session) paper at the 2008 AES Convention at San Francisco.  The method is based on a concept by Malcolm Hawksford, and would appear to be generally sound.  However, the mechanics of the correlation process are not described in the paper and thus it is hard to say how relevant it may be in determining the ranking shown.  Likewise the impact of the 'alignment process'.  It also does not explain the reference (0dB points) for both measurements.  It would also appear that development of this program ceased in September 2008.

The use of a 10-pass method in an attempt to amplify differences may be less reliable than a single pass.  The original paper does not propose multiple pass testing, and is indeed focussed on evaluating a single change.  It is also worth looking at how little difference in gain or phase is required to produce a significant output in the difference file.

Like any experiment, the usefulness of the results depends on the rigour with which the tests were carried out and evaluated.  And like all scientific investigations, it is only useful if independent duplication of these tests by others produce similar results.  And if the test method itself was really useful, I would have expected by now to have seen it taken up by the professional audio testing industry.

So far, my response would be 'noted with interest'.

*Correction: An oversight on my part means that this observation is not correct.

De gustibus - et sonus - non est disputandum

4 (edited by panatrope 2012-02-19 00:41:33)

Re: Fireface UFX converter - bad quality?

As a follow up to this, I engaged in the thread and undertook a further review of the methodology and results.  I put a number of questions to the originator of the post on the consistency of the results and the meaningfulness of the AudioDiff program analysis.  The response was along the lines of avoidance, obfuscation, and denigration ("shoot the messenger"), and the same response has been observed to others who also sought to dispute with the findings.  The originator also appears to lack the necessary technical background to allow him to undertake such an analysis.  The originator has also acquired cult status, particular from followers whose unit rank high in the testing, and accept the results uncritically.

For the record, I think the AudioDiff tool can produce useful results in detecting differences between input and output files from a particular audio process, but the results depend on the testing configuration and test material. 

What is not clear is whether AudioDiff can carry out the amplitude and phase alignment and cancellation process to sufficient precision to evaluate a precision device like a modern day A-D or D-A convertor.  The original tester does not offer any convincing demonstration that this is the case.  I am currently considering whether it is sufficiently interesting to do some simple testing of the AudioDiff process to reveal its objective limits in this type of application.  I am sure that if it did offer useful information, RME would be using it by now.

My present opinion is that AudioDiff is misapplied in this instance and the results as presented are currently meaningless.  (However, I stand to be corrected.)  The UFX (and most of the others tested) have much better performance than AudioDiff can measure with the necessary accuracy.

I am reminded of the words of the 19th century French-born but American resident writer and political philosopher Alexis de Tocqueville, who observed that the public will prefer to accept a simple lie rather than a complex truth.

De gustibus - et sonus - non est disputandum

5 (edited by drainaudio 2012-02-20 16:15:05)

Re: Fireface UFX converter - bad quality?

Yaaaaaawwwwwwn :roll

The originator of that Gearslutz thread (NMS) seems to be on a 1 man mission to prove to himself that his MOTU 828MKII is an amazing piece of gear via a "reality distortion field" (something I'm learning about via the Steve Jobs autobiography).

Having built many MOTU based playback & keyboard setups over the last 10 years (& sorry to big up my credibility for sake of argument but I doubt NMS has the experience of touring globally, gigs to 80,000+ people, biggest global music-related TV shows etc.....I mean seriously has he even been on a private jet??) I can say this:

Yes they (MOTU) are incredibly reliable & functional with rock solid drivers - I have only had 1 failed unit (out of 30+) in that period of time & it was DOA. ---- actually I just got back from a show in Russia, outdoors at a ski resort in -15 degrees & the LCD's were a little slow but the interfaces were fine :-)
Yes MOTU are super friendly & offer great support - I have personally met members of the MOTU team.
Overall a really good, reliable product....

But, they do not sound like the UFX in terms of audio quality or provide the functionality of TotalMix (in the hardware console style that I like) & that's why I personally own/use the UFX despite being able to buy MOTU gear at prices way below retail.

I feel the MOTU gear to be a little harsh to the critical ear, whereas the UFX gives me more of a true representation of what I'm recording & mixing - in terms of what I want to hear & totally IMO.
The difference is subtle (hence why in a live environment for instance it's negligible & cost, support & ease of replacement are bigger issues for me) but it does exist in the same way I'm not too fond of the "sound" of Apogee gear.

At the end of the day how does the UFX sound to your ears & what are the results that you achieve with it???
That is all that matters......huge amounts of time spent by x-person writing posts about how some test says the UFX is blah....blah....blah is totally irrelevant - I don't see any links to his incredible projects recorded with the MOTU 828MKII btw........frankly I doubt they even exist..

If you like the UFX being part of your workflow & it sounds good to you then put this dubious "test" out of your mind and make music!!

Re: Fireface UFX converter - bad quality?

It was an early part of my engineering training that "knowledge without measurement is knowledge of a meagre kind", so you will have take that into account with what I say.

I have picked up a separate thread (not as original poster) that focusses more on the AudioDiff program and its capabilities,but I am using my UFX as one of the test subjects.

I buy equipment like the UFX based equally on features and performance, as I infer that you do as well.  I have used some MOTU in the past, and my main quibble is that MOTU do not currently appear to publish any performance specifications for their equipment, in contrast to RME (and others) who provide (usually) comprehensive specifications, against which they are prepared to be held accountable. 

And I am trying to relate performance (as published by RME) against the results obtained using the AudioDiff program, in a scientific manner.  I have to keep reminding myself that GS is not a scientific forum - part of it could be, but at the moment it is not.

But hey - you get to meet some really interesting people on this forum!

De gustibus - et sonus - non est disputandum

Re: Fireface UFX converter - bad quality?

"Excuse me while I kiss the sky" said Jimmy as he laid down another track on his crappy 4 track tape recorder. All the while they keep measuring and measuring 'til the day they die leaving behind nothing worthy of listening in brilliantly crystal digital clarity.

Re: Fireface UFX converter - bad quality?

@panatrope - totally hear you & I had a very quick look at the reply to your post on that Gearslutz thread where I think you asked some pretty relevant questions & got chided as being apparently unable to understand the software.

A MOTU 828MKII does not sound like a UFX whichever way you slice it & ears not some "measurement software" is plenty enough to tell you that.
Unfortunately the biggest downfall of the internet is the platform it provides for misinformation & at times absolute bs - the people that really know what they are doing/talking about don't have time or the inclination to get involved in huge debates with keyboard warriors who think they know it all based on the ability to spend a short period of time trawling the internet & forming "expert" opinions vs. the traditional route of years of actual experience..

Oh well, never mind, it's a no win situation....like cockroaches you deal with one, another 20 pop up.

Again to the original poster - put it out of your mind, you wisely bought a great bit of gear, spend time learning to use it well vs. dwelling on what someone who is clearly ill-informed & probably spends more time on internet forums than actually being creative thinks of it..

9 (edited by panatrope 2012-02-21 23:40:26)

Re: Fireface UFX converter - bad quality?

gamerx wrote:

"Excuse me while I kiss the sky" said Jimmy as he laid down another track on his crappy 4 track tape recorder. All the while they keep measuring and measuring 'til the day they die leaving behind nothing worthy of listening in brilliantly crystal digital clarity.

Content is key, I agree.  That's why some of my favourite recordings come from 1920's acoustic records.  But for those who want quality of delivery to match quality of performance, then listening and measuring is unavoidable. And if you need to measure, you want it to be accurate and meaningful.  Like the performance ...

Somewhere in the Good Book (at least the King James version), it is written:  "The heart is deceitful and desperately wicked.  Know ye it."  Take away the 'h' and the 't' from 'heart' and it is still true.

De gustibus - et sonus - non est disputandum

Re: Fireface UFX converter - bad quality?

Thank you all, and especially you, Panatrope, for your contribution. i followed the gearslutz thread and the time and effort you invested in those things is very much appreciated on my side. i really like my ufx feature AND soundwise, nonetheless it's making me a bit nervous if someone states poor audio quality on a "scientificic" base which i can't comment. i am a musician and producer and don't dive deep in the technical aspects of my equipment. you clearly presented yourself as an educated, open minded person, and i'm happy you chimed in. after all, i don't want to bother about having to buy a motu 828 mkii for my conversion duties because the ufx sounds poor in comparison. personally i think the ufx sounds great. you all gave me confidence that i still can trust this impression.

Regards,

Fishmac

Re: Fireface UFX converter - bad quality?

Thanks for your kind remarks.

I went into that thread not to boost the UFX, nor to denigrate the tester.  I went in there because I thought that the value of test results did not make sense, and that they did not show that the measurements relate closely to 'transparency'.  They may mean something, but not that.  So using it as a base to decide which interface to buy would not be reliable, and could be misleading.

However, I do think that AudioDifference testing, when conducted correctly, can produce useful information.  So I'm not abandoning it, but carrying on (at my own pace) to see where its limits lie.  And who knows, I might have a couple of interesting questions for RME about the results my interfaces give  ... :-)

De gustibus - et sonus - non est disputandum

Re: Fireface UFX converter - bad quality?

panatrope wrote:

Thanks for your kind remarks.

I went into that thread not to boost the UFX, nor to denigrate the tester.  I went in there because I thought that the value of test results did not make sense, and that they did not show that the measurements relate closely to 'transparency'.  They may mean something, but not that.  So using it as a base to decide which interface to buy would not be reliable, and could be misleading.

However, I do think that AudioDifference testing, when conducted correctly, can produce useful information.  So I'm not abandoning it, but carrying on (at my own pace) to see where its limits lie.  And who knows, I might have a couple of interesting questions for RME about the results my interfaces give  ... :-)

^^ I'd certainly be interested in seeing what you came up with in a real-world use scenario - i.e. not a 10 pass loopback test :roll
Please post once you have some info.

Re: Fireface UFX converter - bad quality?

drainaudio wrote:

^^ I'd certainly be interested in seeing what you came up with in a real-world use scenario - i.e. not a 10 pass loopback test :roll
Please post once you have some info.

A loopback test does have some convenient points, not least of which is that sampling rates will be identical.  Obviously it is hard to do tests on the A/D or D/A independently (I can use a Benchmark DAC1 as an alternative DAC).  But as an indication of direction, I'm first trying to see if AudioDiff can deliver results consistent with published specs for THD+noise.  Results so far suggest that the cancellation acheivable by AudioDiff is not enough to give a reliable reading - it is very dependant on process.  In my view, when it can do this 'simple' test with credible results, then we can think about tests with program material such as is used in the GS rankings.

And that AudioDiff gives perfect (expected) cancellation on a digital loopback (proves that the digital path to and from the interface does not introduce any differences), but things change drastically when a D/A-A/D is part of the loop.  So right now, the question is 'why'?

As I say, a work in progress.  Comments and suggestions on test method always welcome.

De gustibus - et sonus - non est disputandum

Re: Fireface UFX converter - bad quality?

panatrope wrote:

but things change drastically when a D/A-A/D is part of the loop.  So right now, the question is 'why'?

Seems like perfect common sense - most reference publications on using a DAW advise against leaving the box once you are within the digital domain - A/D in & then possibly D/A - A/D at a push if you are going to using an analogue summing device at final mix.
How can anyone think constant passes of a source through A/D-D/A will not result in some form of signal degradation.

Just like the analogue days when many a session was ruined by constant re-takes, wear on tape stock etc (I recall there being a good documentary on the recording of a Fleetwood Mac album - might have been Rumours - where the drum tracks had deteriorated by the end of tracking to the point where they had to be saved using a backup - which had fortunately been made - of the original takes/comps).

I can't think of any situation where I would "loopback" my source material in a project 10 times - it's just ludicrous as a test subject, somewhat akin to judging an F1 car on how much shopping you can fit in the boot. ed:

Re: Fireface UFX converter - bad quality?

Interesting story.

My approach is one A-d conversion and one D-A conversion, the former at the recording, the latter for monitoring or in the listener's player.  The tester's premise was that it would amplify the differences.  Unfortunately the amount of mud stirred up makes it hard to see clearly what is happening.

If AudioDiff is so accurate, it should be able to see this in a single pass.  There is something happening in a D-A/A-D loop which at the moment appears unexpected.  The quest is to find out what it is, then we can start to examine what it contributes to loss of transparency.

Does an F1 car have a boot? HeadScratch

De gustibus - et sonus - non est disputandum

Re: Fireface UFX converter - bad quality?

panatrope wrote:

Does an F1 car have a boot? HeadScratch

A very small one - you can only fit a spare pair of underpants.....

17 (edited by Timur Born 2012-02-28 11:34:19)

Re: Fireface UFX converter - bad quality?

panatrope wrote:

And that AudioDiff gives perfect (expected) cancellation on a digital loopback (proves that the digital path to and from the interface does not introduce any differences), but things change drastically when a D/A-A/D is part of the loop.  So right now, the question is 'why'?

As I say, a work in progress.  Comments and suggestions on test method always welcome.

Last year I stumbled about an AudioDiff thread on GS, too. Back then it indirectly "revealed" that the Babyface uses a high-pass filter in its input stage. I write "indirectly" because AudioDiff did not give any information about this, but only showed that "something" was different.

What I did back then was set up a manual loop-back test via DAW software, and that is what I suggest you to do. You should notice then that it seems impossible to align output and input to perfect cancellation on a sample-basis, there seem to be time-differences on an inter-sample basis introduces by the AD/DA conversion. This would be the reason why a digital loop-back cancels perfectly in comparison.

I have to admit that I did not spent enough time with AudioDiff and the little time I spent I was unable to understand how time-alignment (cancellation) was achieved by the software/user. But the process seems nontransparent enough for me not to trust it over my manual measurements (where at least I can try to get as close to 0-1 samples difference as possible).

Re: Fireface UFX converter - bad quality?

I really must write a proper report about what I have done with AudioDiff.  But suffice to say, I am happy at the moment that the internal time-alignment process is good for sub-sample interval time alignment (it has internal setting to set the alignment resolution down to 120ps).  I used iZotope SRC to up convert a test signal to 192kHz, removed 11 samples (prime number, no ratio to either 192K or 44K1) and converted back, and found a precise alignment of the offset and excellent cancellation.  I also tested the cancellation ability by adding, while at 192kHz, a controlled amount of pink noise (-75dBfs rms).  After SRC back to 44K1, the original test signal was cancelled sufficient to apparently leave only the added pink noise at around -75dBfs and there was no identifiable residual of the original test signal.  This appears to be a good result.

Now this of course was done only in the digital domain.  Things get interesting with a D-A/A-D in the loop.   Jitter comes into question, possibly leading to a loss of "coherence", as one French correspondent on GS puts it.  Previous work as documented in an earlier AES paper (Dunn) came up with a figure of 120ps rms jitter as equivalent to the level of quantisation noise on a 16-bit recording, so as jitter is another form of 'quantising noise" we should see an added noise of this level for this amount of jitter..  Most companies that quote specs have a figure much less than this for their clocks. 

So, I also want to check if jitter is a cause of the inability to completely cancel the test tone in the "THD plus noise" test (given that spectrograms of the harmonic components and noise floor in the output file appear to be as expected). Should we see some evidence of this in the shape of the noise floor, particularly due to jitter components out to say 20 or 100Hz?   (BTW, a loopback test of the UFX - AN out 3,4 high gain to AN in 7,8 low gain) gave results for added harmonics that are about what I expected, based on the published specs.)

Low jitter has previously been linked anecdotally with increased 'transparency'.  If jitter is one of the main reasons for the level of differences detected by AudioDiff, then maybe there is a basis for the tester's contention that such testing can correlate with 'transparency'.  But I think a whole lot more work has to be done to make that conclusion reliable.

De gustibus - et sonus - non est disputandum

Re: Fireface UFX converter - bad quality?

Timur Born wrote:

Last year I stumbled about an AudioDiff thread on GS, too. Back then it indirectly "revealed" that the Babyface uses a high-pass filter in its input stage. I write "indirectly" because AudioDiff did not give any information about this, but only showed that "something" was different.

What I did back then was set up a manual loop-back test via DAW software, and that is what I suggest you to do.

OK, I might get out the BabyFace and measure it for comparison.  What frequency for the high-pass filter?  Because both BF and UFX run at once on USB it also means I can mix and match A-D and D-A to see if there is any systematic variation. 

My test method currently uses REAPER to play out the test file and record the looped back signal.  I think this is what you are suggesting.  Prior to the line-out/line-in loop, I checked with loopback via TMFX and via AES out/AES in to see if the path to and from the UFX introduced any differences.  A perfect null in both cases, so zero effect.  Different delay offsets, of course.

De gustibus - et sonus - non est disputandum

20

Re: Fireface UFX converter - bad quality?

panatrope wrote:

Jitter comes into question, possibly leading to a loss of "coherence", as one French correspondent on GS puts it. Previous work as documented in an earlier AES paper (Dunn) came up with a figure of 120ps rms jitter as equivalent to the level of quantisation noise on a 16-bit recording, so as jitter is another form of 'quantising noise" we should see an added noise of this level for this amount of jitter.

That is the raw clock jitter within the AD-conversion process (sampling jitter), which can only be measured by a high-resolution FFT of the digitized signal, and is a quite theoretical value. But: If there would be high jitter, then you would see it in the measurements. The FFT is clean, the noise floor (RMS) is at -112 dBu, far more down than the 96 dB (for 120ps) of that paper, or in other words: the jitter effects are lower than the noise and THD produced by the ADC itself. Jitter can not explain the measurement results.

Regards
Matthias Carstens
RME

Re: Fireface UFX converter - bad quality?

panatrope wrote:

...I am happy at the moment that the internal time-alignment process is good for sub-sample interval time alignment (it has internal setting to set the alignment resolution down to 120ps).  I used iZotope SRC to up convert a test signal to 192kHz, removed 11 samples (prime number, no ratio to either 192K or 44K1) and converted back...

I assume that in order to time-align sub-sample intervals AudioDiff has to oversample aka sample-rate convert. The question is how this is implemented compared to the various other SR conversion algorithms out there (all of which come with their own advantages and disadvantages)?

Did anyone check yet if the test-signal itself makes any difference for the results (like more transient signals vs. less transient ones etc.)?

Re: Fireface UFX converter - bad quality?

MC wrote:

That is the raw clock jitter within the AD-conversion process (sampling jitter), which can only be measured by a high-resolution FFT of the digitized signal, and is a quite theoretical value. But: If there would be high jitter, then you would see it in the measurements. The FFT is clean, the noise floor (RMS) is at -112 dBu, far more down than the 96 dB (for 120ps) of that paper, or in other words: the jitter effects are lower than the noise and THD produced by the ADC itself. Jitter can not explain the measurement results.

Thank you for the input.

This was my expectation entirely, but of course I have to observe that for my self.  The figure of 120ps was based on a test tone of 20kHz, and of course the noise for a lower frequency would be correspondingly less, assuming it is a quantising noise-like distortion.  (John Watkinson's "An Introduction to Digital Audio (2nd Ed.)"  has a useful nomogram on p.107 to help point out the noise level one would expect from various levels of jitter.)  Considering it as a form of phase modulation would produce sidebands around the test tone, which would also be revealed by high resolution FFT spectral analysis.

Thankfully, there are many high-quality spectral analysis tools at low cost (some even free) available to assist in this work.  (Not to mention DigiCheck, of course).

De gustibus - et sonus - non est disputandum

23 (edited by panatrope 2012-02-29 23:57:58)

Re: Fireface UFX converter - bad quality?

Timur Born wrote:

I assume that in order to time-align sub-sample intervals AudioDiff has to oversample aka sample-rate convert. The question is how this is implemented compared to the various other SR conversion algorithms out there (all of which come with their own advantages and disadvantages)?

Did anyone check yet if the test-signal itself makes any difference for the results (like more transient signals vs. less transient ones etc.)?

The draft AES paper from 2008 does give some details about what AudioDiff does.  It takes 2.5 sec (adjustable) samples from the file and does an FFT which it manipulates in the frequency domain to produce a timeshift to nanosecond resolution which results in optimum correlation between the reference and compared files.  It reports the value of timeshift in the output result text.  (And in its operations it uses a 4x up-sampled version of the files - integer up-sampling usually has no harmful byproducts.)

I have tried it with both test tone and music.  Working exclusively in the digital domain it produces good results.  With conversion between digital and analog in the process, life is more interesting.  It also needs some tweaking of the AudioDiff settings.

I would recommend downloading the program and exploring what it can do - it will have uses outside testing interfaces.  Comparing microphones is another possibility I am considering (and possibly opening up a whole new can of worms .... fryingpan ).

The thing to avoid is the American habit of looking to it for a single number solution to the world's ills.  Remember the words of H L Mencken:  "For every complex problem, there will always be a solution that is simple, cheap ... and wrong."

De gustibus - et sonus - non est disputandum

Re: Fireface UFX converter - bad quality?

op-amp-measurements

www.bonisaudio.com

Re: Fireface UFX converter - bad quality?

Sigh!!  Even selling the Nagra would probably not even give me the deposit for a d-Scope ...

De gustibus - et sonus - non est disputandum

26 (edited by WKG 2012-05-03 17:58:42)

Re: Fireface UFX converter - bad quality?

Have there been any further revelations on the UFX on this topic? Any clarification from RME? I've been nosing around the GS thread and while interesting I don't think it is revealing a complete and accurate picture of the UFX or any of the units tested, let alone in a real world application setting. I am all for testing/info and any insight into what's going on "under the hood" with the UFX and any of the units shown but partial information is misleading.

I've had my UFX for a while now and it's a great unit, stellar audio quality, stability is excellent, no issues whatsoever in regards to anything, and the ARC is very handy indeed.

Re: Fireface UFX converter - bad quality?

Likewise my UFX is performing very well.

I still maintain my criticisms of the GS "test" methodology, particularly the assertion that measurements equate with "transparency".  Difference testing has limitations, and test need to be designed around these.  Until more work is done to identify what is being measured (even in simple single-frequency tests which fail to produce results consistent with existing THD+noise measurements), nobody should make any reliance on such tests for purchasing decisions.

And there is more to a UFX than just distortion and noise measurements.

De gustibus - et sonus - non est disputandum

28

Re: Fireface UFX converter - bad quality?

Unfortunately I have neither the time nor the technical background to properly address all the issues in the thread. It would be nice as it seems a huge disservice to the recording community at large to provide an list of quality rankings based on partial and inaccurate "ultimate" test results.

Re: Fireface UFX converter - bad quality?

I record, weekly, 17 swing musicians-13 of them blow horns. Trumpets and baritone saxophone/trombones are especially difficult to record-well.  I can testify that the UFX (in back of hi quality mics) records, indeed, very high quality tracks.  Where there may be some confusion is upon monitoring. 

Only two tracks of D to A are needed for typical basic monitoring/mixing.  While I, initially, used an UFX for D to A it's no disrespect to RME to realize that I was squeezing my entire 22 track mix through less than $200 of D to A converters (divide the UFX street price by all its D to A and A to D converters).

So I stepped up to an ultimate quality D to A-the Weiss DAC 202 (about $7700). I gained the flexibility of a digital input preamp, headphone monitor and calibrated master monitor level while retiring (reselling!) my "Golden Ears" analogue bypass preamp. The different in quality was very substantial.

So my experience is that you can take the compact/lightweight UFX into the field and record and, later, mix your files in the digital domain while retaining very high quality. But you may have to pay up for a mastering level D to A, speakers and amps to hear what you have recorded (my PB/mixing rig is $120K +).

Re: Fireface UFX converter - bad quality?

SoundHound wrote:

The different in quality was very substantial.

As we do not have your ears, can you please describe the differences you hear?

I also have an external reference D/A (not as expensive as yours but still highly regarded) and I have been considering doing the loop-back test described in the GS forum, but using the external D/A in comparison to the UFX outputs. (I can possibly use the A/Ds in the Nagra V to make the opposite comparison.)

I still can't say what the new results might mean in terms of 'transparency'.

De gustibus - et sonus - non est disputandum

Re: Fireface UFX converter - bad quality?

Basically, i listen to the horns live and compare the playback, later, to my "sound memory". If such a thing sounds implausible or unscientific I can only say that I have 45 years experience in recording and almost a year with this band on a weekly basis. After some time and experience you hear the sound live and then are in a struggle to record then hear it "right" on playback. It should only take a few seconds to form a reliable acoustic impression.

I want to emphasie the first requirement is to capture the recording in high quality-which the UFX will readily do coupled with good mics and technique. As to playback quality you can always rent an hour of studio time to audition your recorded session files.  After that you can make price/quality decisions for playback equipment.

Your monitor amplifiers and speakers are key to a good mixdown since if you can't hear it you can't mix it.  To save money you could consider self powered near field monitors because it's cheaper to fill up a small space rather than a larger one.  However, there seems to be no free lunch in D to A converters.

I find that headphones, despite all the new accessories to be inadequate for music mixing (I mixed dialogue on Beyer DT-48s for 35 years).  But they can be useful to solo an input to check for noise or distortion while recording.  Ultimately, with a very high end monitoring system, you will even hear more detail than in the popular headsets.

The Weiss 202 DAC has special circuits to control jitter. The result, to my ear, is much firmer bass, smoother highs and often more depth to the soundstage. When I toured the 2012 CES uber HiFI suites I could often hear the effects of a low end D to A converters.

Of special note is that the Weiss 202 has a handy digital side chain which is very useful for system EQ. Ideal results can be obtained with the inexpensive Behringer DEQ2496 (note that this is possible only because the DEQ's inexpensive D to A and A to D converters are out of circuit)l  A white paper and other reference material is on the Daniel Weiss site. It seems the last few pico seconds of jitter are very important.

Re: Fireface UFX converter - bad quality?

Thank you for your explanation.

So, the differences you can describe are "much firmer bass, smoother highs and often more depth to the soundstage."  To me, these could be associated with (among other things) lf phase response, anti-aliasing filter response, and low level phase and amplitude linearity, all characteristics that should be capable of being observed with objective measurements.  However, the history of audio is littered with examples of "I can hear it but I can't measure it"  - the ability to link perceived differences and physical reality.

The proponents of the Audio Difference testing method have postulated that devices can be ranked in terms of 'transparency' by the score achieved in the test.  In my view, they have yet to justify this association, and they have not identified the origin of the "differences" that they have documented.

Their testing methodology does not allow reliable differentiation between the A/D and D/A process included in the chain.  As your observations suggest that the UFX A/D process is satisfactory (to you) but not the D/A process, maybe a comparative DiffTest measurement of a loop comprising the UFX on its own, and the input looped to the output of a Weiss (or other 'reference') D/A could be interesting.

But the problem still remains identifying the cause of any differences measured, and accurately relating these to the subjective observations you have made.   As it has been throughout the history of audio.

De gustibus - et sonus - non est disputandum

Re: Fireface UFX converter - bad quality?

I'd guess jitter is more important at the AD as any jitter that manifests itself there will be encoded with the bits - and no amount of "Golden DAC" will be able to recover the jittery encoding.

So 800ps (or almost 1us as RME specs the UFX's internal clock) of AD jitter is acceptable to you from the UFX (and the resultant files that have 800ps of jitter "hard coded" into the bits), but you are saying that jitter that is TWO ORDERS OF MAGNITUDE less at the DAC ("last few pico seconds of jitter are very important") is still objectionable by contrast?

I wonder if you can trade off ADC jitter for DAC jitter (low 100ps range on ADC but 800ps on DAC) - or if Jitter related artifacts aren't what you are experiencing at all?  I'd again assume low jitter at the ADC is MORE beneficial as any susequent DSP processing and is then working off a more accurate representation of the audio it is processing.  Also, if you have a lower jitter ADC, the overdubs you do will be more closely related in terms of their jitter spread across takes.

Thoughts?

There's so much we don't know about Digital Audio!

cool

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Re: Fireface UFX converter - bad quality?

So sorry gentlemen! I am not an expert in digital testing and wished only to indicate my experience as to UFX record "suitability" on a live Swing band-with 13 difficult to record horns. Obviously,  I find the UFX' A to D's, encoded jitter more than acceptable.

There are A to Ds beyond my price class (and logistical management ability) but this forum, in large part, is devoted to the uber portable and compact RME gear that I find such a value.  I hope that I more than implied this when I compared the UFX' $2.2K cost with its 24 (is it?) converters to the $7.7K of the Weiss' two (note that the Weiss two channel mastering A to D is about $9K).

My reply post was to a question of how to describe, in words, the difference in sound between two D to A converters-doomed to failure-obviously. My Jitter(y) speculation was my "take" on what I had read. Yes I do have the impression that it's eaiser to A to D for recording than D to A for playback.  However, I really have a limited amout of experience for such an observation and would rely on others for a such a conclusion.

Maybe a more useful comparative could be that my "IT guy" (civilian computer expert) was present when I made the change over to the Weiss DAC.  He knew of my financial ambivalence in buying such an expensive box (the price of two two or more very fine desktop computers to him) but was astonished at the difference in sound-to his untrained ears.

For some decades I had tested analogue devices (notably speaker power amps and small signal amps/preamps) with the best, then, equipment. However, today as then, there are things that I and others can't measure but which do manifest themselves in different and occassionally "better" sound. 

For this I would allude to my 8 amplifer combinations over two years as I escalated in cost, if not measured RMS watts, to drive my B&W monitor speakers. For such acoustic description nicities I would, in the future, refer you to those Golden Ears HiFi wordsmiths-just take your pick of their lush prose.

At least, for now, I am pausing in amplifer upgrades with the stasis of two monoblocked Burmester Mk IIIs for 350 hz up (350hz down is driven by class H "roadie" amps with 4 times the RMS power and 1/100 the cost-because I can't tell the difference in the lower frequencies)).

It's also notable that the wire I use to connect the Burmesters to the B&Ws costs twice as much as the four Tapcos (2500/2800 RMS watts monoblocked-each) used for the low end of the B&Ws and Subs.
Yes, I did try the cheap wire, the expensive wire and the now this more expensive wire.

I paid up for the wire because I could hear the difference in a few seconds and, yes, my IT guy can hear the difference too as well as my Pro Tools engineer.  I am, complaisently, happy with the wire that cost only $2-3k per set ( atmdiscount 2 set in use) and am loath to demo the stuff that's a order of magnititude more.  I also haven't listened to the Weiss ADC 2 (Lavery Gold, etc.) because I would need ten or eleven of them (about $90K+), a rack, a truck and an assistant to help me.

I don't know how you test "wire" either-to predict what it sounds like. So for those of you involved in such ambitious testing, whether digital or analogue, more power to you. I will be interesting in your methods, data and conclusions.

Re: Fireface UFX converter - bad quality?

Randyman... wrote:

So 800ps (or almost 1us as RME specs the UFX's internal clock)

800 ps is almost 1 ns, which is less than 1/20000 the sampling step at 44.1 kHz. I hardly believe that the 'last picosecouds' could be as important as M. Weiss would have said.

36 (edited by panatrope 2012-05-14 00:58:48)

Re: Fireface UFX converter - bad quality?

Sampling places a point in both space (voltage) and time.  Accurately rendering the phase of a signal depends on resolving time to the same accuracy as voltage.  Current systems do voltage at around -120dB. 

See John Watkinson's "An Introduction to Digital Audio" (2nd ed.) pp106-107.  For a 20kHz signal in 16-bit system, timing jitter needs to be limited to 120ps.  For lower frequencies, the jitter limit is correspondingly higher.  A 1ns pk-pk jitter on a full-scale 3kHz signal will result in a theoretical signal/noise ratio equivalent to a 18-bit resolution (around -110dB).

Using the AudioDiff test on a single pass through the UFX (AN7-8 out to AN1-2 in) with a digitally-generated single frequency 997Hz signal at -1dBfs, the best cancellation of the fundamental that I could observe with the spectrum analyser (16,384 resolution/Blackman-Harris) of either Sound Forge or iZotope RX II was about -75dB (compared to perfect cancellation on a purely digital path through the same device).  The harmonic distortion components were clearly identifiable at about the expected levels.  Sidebands could be observed at ±200Hz at a level below -100dBfs, suggesting that if they were due to jitter, it might be mains-frequency related.  (No significant mains-related baseband signals were noted.)

I would regard this result as not bad for the capability of the measuring methods available to me.  It broadly supports the specs published for the UFX.  Why AudioDiff cannot more accurately cancel the fundamental when an analog link is included in the chain is a question of interest - whether it is a limitation of the program or whether it is a product of unknown spurious distortion which might (or might not) be jitter related. 

And what jitter contributes to the rating of audio performance ('transparency' or whatever) is what we are concerned with.  Experienced ears can hear different things, but there are so many other factors that influence perception.  It just needs the reasons relating engineering performance and subjective assessment to be discovered, and if you can do that "you're a better man than I am, Gunga Din!"

De gustibus - et sonus - non est disputandum

Re: Fireface UFX converter - bad quality?

The "test" on Gearslutz is so contrary to my experience (based on equipment on that list that I have heard myself) that I completely disregarded it and went out and bought a UFX.   So far, I put it in around the same class as the Lynx Aurora in terms of sound quality.  Though I prefer the UFX because the Aurora is a little bright sounding, and not in a good way, IMO.
Though I'm a undecided about the UFXs low end reach, it replicates a sense of front to back depth wonderfully and picks up nice subtleties like harmonic overtones and transients.

Re: Fireface UFX converter - bad quality?

SoundHound wrote:

There are A to Ds beyond my price class (and logistical management ability) but this forum, in large part, is devoted to the uber portable and compact RME gear that I find such a value.  I hope that I more than implied this when I compared the UFX' $2.2K cost with its 24 (is it?) converters to the $7.7K of the Weiss' two (note that the Weiss two channel mastering A to D is about $9K).

I was discussing this with a colleague of mine who has long experience in classical musical and audio production. He arranged a comparative test of the DACs of the Prism Orpheus, the Nagra VI and the Weiss with his new Forsell DACs, replaying the same minimalistically recorded digital material into the same set of reference speakers.  His opinion was the Forsell (considerably cheaper than the Weiss, more expensive than Orpheus or UFX) was superior (descriptors "definition" "detail" and "depth") and the Weiss was the inferior ("muffled").  His reported impressions, obviously at odds with your experience. 

What measurements could we possibly devise to objectively explain the different perceptions?  Or do I revert to my old signature quotation - de gustibus non disputandum est - it is useless to argue about taste?

De gustibus - et sonus - non est disputandum

Re: Fireface UFX converter - bad quality?

BOWIE wrote:

The "test" on Gearslutz is so contrary to my experience (based on equipment on that list that I have heard myself) that I completely disregarded it and went out and bought a UFX.

Strong move (as a certain GS correspondent is bound to remark). 

BTW, I think I have found a fundamental flaw in the AudioDiff testing methodology*, which I need to develop a little more technically before talking about it, but would limit the accuracy that can be achieved.  There is a danger in using a measuring tool and relying uncritically on the results it produces without fully understanding what that tool does.  This is, I believe, the case, in the series of tests we are talking about.

(* Like Archimedes, it was a "Eureka" moment in the baths (American = pool), while doing my regular lap swimming routine, an environment which has produced many moments of clarity!)

De gustibus - et sonus - non est disputandum

Re: Fireface UFX converter - bad quality?

Hi, first time here.

I had already decided to buy UFX or UCX. Then i found that loopback thread, and changed my mind. Well, after all I didn't buy anything, because I was so confused about mixed reaction here and there.

But I was curious about the crucial element of that test: Audio DiffMaker. It appeared to me as a one big mystical element that gives the final truth. 

So what was it and what can it do? I wanted to challenge it before I was ready to trust it as a final word.

I've just  made some tests with DiffMaker. If any body is interested with them, you can find them here:

http://www.slapmedia.com/diffmaker/

There's lots of audio examples and graphs, and everything is in total mess. Hopefully you get better idea of what DiffMaker can do and where it can be used. At the moment I have no answer for that.

41 (edited by panatrope 2012-05-23 02:40:51)

Re: Fireface UFX converter - bad quality?

As previous discussion here and elsewhere have indicated, AudioDiff is a tool that attempts to extract and measure differences between related digital audio files.  You can read about it in the paper presented at the 2008 AES Convention.  It appears that the author has done no further work on the program since then.

Bottom line is that it tries to time-align and level-match (as best it can) the audio in the two files, creates a file that contains the difference, and also produces a measure of the correlation (a mathematical process) between the contents - the greater (in a negative sense) the correlation depth, the less difference there is between the files.  Exactly how it does this and how well it does this is known only to the author - and he has said nothing more (as far as I am aware) since 2008.   The correlation depth measurement presently can only be regarded as a magic black box that gives a measurement whose meaning, in regards to perceived audio quality, is still not clear.  The only reliable and meaningful result is -300dB, which means the files are absolutely identical.

The resulting difference file is, in my view, much more meaningful. It does not tell you what causes the difference - frequency response, phase response, jitter.  For example, an anti-rumble low-frequency roll-off may have an effect of a few degrees of phase shift in the band below 100 Hz which is largely inaudible but may alter the waveform sufficiently to prevent precise cancellation  and thus produce an apparently poor measurement.  But it is often very useful to listen to the difference file, and assess how much of the content is due to incomplete cancellation of the original signal.

Look at more conventional measurement as well.  Listen.  Work out if it does what you need for your particular interests.  AudioDiff results cannot be relied on to produce an index of "goodness" on which to rank prospective gear buys.

De gustibus - et sonus - non est disputandum

42

Re: Fireface UFX converter - bad quality?

what about sample accurate null tests......wouldnt that be the best way?

Re: Fireface UFX converter - bad quality?

panatrope wrote:

The correlation depth measurement presently can only be regarded as a magic black box that gives a measurement whose meaning, in regards to perceived audio quality, is still not clear.  The only reliable and meaningful result is -300dB, which means the files are absolutely identical.

I agree totally.

Although I didn't say it explicitly, my main finding with those simple tests was that DiffMaker cannot detect  properly basic changes in frequency response. Even the slightest changes in frequency response curve causes  DiffMaker to give erroneous results. If it cannot handle basic changes in frequency response, there's no sense to expect that it could do more difficult stuff properly.

Re: Fireface UFX converter - bad quality?

Wiz wrote:

what about sample accurate null tests......wouldnt that be the best way?

In essence this is what DiffMaker tries to do. Any difference left after nulling/phase-cancellation is what is measured. Main problem is the "black box" part where users don't know what happens internally versus when you do all this stuff manually.

45 (edited by panatrope 2012-05-24 01:58:17)

Re: Fireface UFX converter - bad quality?

Wiz wrote:

what about sample accurate null tests......wouldn't that be the best way?

My brief tests indicate that it will deliver sub-sample accurate time alignment to -300dB indicated correlation depth to indicate the two files are identical.  I have not checked level match yet.

Behaviour with controlled digitally-added distortion is the next interesting test.

{@Timur - any thoughts about a program or plug-in that can be used to add a (mathematically) controlled amount of second or third harmonic distortion, without affecting phase or frequency response?   Tape simulator was one thought, but these may include phase or amplitude modulation as well.}

De gustibus - et sonus - non est disputandum