NuForce uDAC-2 Drama (detailed measurements) - Page 3

I'm not trying to debate "triple 0" levels of THD. I agree that say .0007% THD is for all practical purposes the same as .007%. A case can even be made that .07% is still inaudible. But the uDAC-2 measures .7% at any setting of its volume control due to the internal DAC clipping problem. There are no zeros between the number 7 and the decimal point. As I've said, there's still considerable debate over what's audible as it depends on lots of variables, but many are documented as hearing 0.1% THD and, in certain cases, even 0.03% has been proven audible. But, overall, 0.5% is a more widely accepted standard of audibility. NuForce is over this level of audibility.

And your references above are the average level below 0 dBFS not the peak level. They're entirely different things. The higher the average level (which has been steadily pushed up over the years) the more the peaks hit 0 dBFS. Below is the music clip I used in the example for my review. It has a peak level of 0 dBFS (everywhere you see the blue lines hitting 100%) and an average (RMS) level of -12 dBFS. If you look at a track with an average level of -6 dBFS (and there are plenty around) it's "slammed" against 0 dBFS much of the time just as Wildstar reported. It's a fact the uDAC-2 will have ten to fifty times more distortion on each and every one of the peaks due to the way it's designed.

And you're confusing dynamic range as well. The lower the dynamic range (like the 20 dB number you quote) the more the signal will hit 0 dBFS as the recording is more compressed over a smaller total range.

Here's the popular Lady Gaga track "Just Dance" exactly as it's on the CD as shown in Audacity. Audacity is free. Anyone can download it and view their music as shown here. Below you can see what others have said about the music hitting 0 dBFS frequently. If you just put the CD in your drive and pushed play, this what is sent to the uDAC-2 and it will have what most consider high distortion for much of the track:

Quote:

Originally Posted by Modo 

@nvawguy

How does the uDAC-2 compare to an integrated sound card, the kind it would replace in a semi-portable laptop rig?

The internal sound hardware in laptops varies widely. So it's impossible to make a generalization. Some laptops certainly have better internal sound performance than the uDAC-2 can manage. Some, I'm sure are even worse. I've never seen even one, however, that clips 0 dBFS signals or has 10 dB of channel balance error like the uDAC-2 does. Generally, if you're happy with the sound of your laptop's headphone jack with your particular headphones, I wouldn't complicate things with an outboard DAC. And if you're not, I wouldn't buy a uDAC-2 but instead explore better options such as the suggestions I made in the review.

Quote:

Originally Posted by holland 

That's incorrect.  0dBFS is not like the top speed of a car, so it's not a good analogy.  It is hit regularly unless you use "replay gain".  Is NuForce unique here?  I don't believe so.  I'd fathom clipping with 0dBFS is more common than not.  This is, in effect, why replay gain exists.  The loudness war, compressing the dynamic range, and then boosting the overall levels to clipping, is a major contributor.

No it's not why replay gain exists, and 0 dBFS clipping in a DAC is very UNcommon. I challenge anyone to show me credible results of another device that clips in the same way the uDAC-2 does? I've probably measured close to 100 digital devices and I've never seen it before.

As I've tried to explain, 0 dBFS is the reference used in design, measurement, testing, etc. It's the cornerstone that everything else is built off of and referenced to. It's NOT normal for a DAC to screw it up. You can't reference to a "zero" level as it would be lost in the noise. And trying to use some intermediate value in the middle would create other inaccuracies and confusion. So 0 dBFS is the defacto standard and the uDAC-2 doesn't handle it well.

What I think you're getting confused is that some recordings clip at 0 dBFS. There are some ways certain software tries to "un clip" these recordings but the damage was already done when the CD was mastered. This has nothing to do with anything in the playback signal chain like the uDAC-2. It's done by the record label.

Replay gain exists because the average level varies a lot from track to track. Replay gain lets a software program analyze all the tracks and normalize (where possible) to a similar average listening volume as perceived by a human. There are lots of references on this. Please let me know if you need one?

Quote:

Originally Posted by bcwang 

I'd like to hear these samples.  Sounds like if you played back 44.1/16 on each one and used the benchmark ADC to record at 24/192 or at least 24/96, that would help.

 

-Same analog and usb cables

-Same output level for each source (if adjustable)

-provide the original reference sample as well if possible.

Thanks for the vote and your input. I agree with most of your comments but not the sampling rate. The fact is 95+% of the people listening won't be able to properly play back a 24/96 file let alone a 24/192 file. And those files would be many times larger than a 44/16 file which makes them much slower to download.

So rather than the vast majority of people having to sample rate convert the test files to 44/16, which may create its own artifacts and audible problems, I think it's better to record them in 44/16 so they can remain bit accurate just as the ADC1 captured them all the way to the DAC that's decoding them on the other end. I believe that will be more transparent.

And, if you're interested, extensive subjective testing has been done on Hydrogen Audio and elsewhere with respect to 24/96 vs 44/16 and the general consensus was there's no advantage for just recording and listening at 24/96. There is a advantage if you plan to edit/process the file as an intermediate step (such as a musician mastering their music) but not just for simple playback.