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Review and Measurements of Audio-gd NFB2 192 DAC

amirm

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#1
This is a review and detailed measurements of the Audio-gd NFB2 192 khz DAC. It is on kind loan from a member. It costs US $450 from Audio-gd website.

The overall package while heavy and functional, is not that exciting:

Audio-gd NFB2 192 kHz DAC Audio Review.jpg

The back panel has the usual connection plus the current mode "ACSS" proprietary connectors which I did not test:

Audio-gd NFB2 192 kHz DAC Back Panel Audio Review.jpg

I see no safety or regulatory marks on the unit which is concerning for mains operated units (i.e. NOT using external power supplies).

The unit was plug-and-play on Windows although oddly exposes inputs in addition to outputs! That threw off ASIO4ALL wrapper I use to talk to it in my analyzer. Once I shut down the input, it worked fine.

"NFB" stands for no negative feedback which Audio-gd goes to great lengths to sing its virtues:

1560541700522.png


DAC Audio Measurements
As usual, we start with our dashboard using USB Input:
Audio-gd NFB2 192 kHz DAC Audio Measurements.png


We have about 1 dB of headroom above our nominal output voltage of 2 volts which is nice. Reducing the input by 1 dB did not materially change the performance. High harmonic distortion severely limits performance. This will increase the energy in higher frequencies and will cause some brightness/harshness although most people probably can't tell.

The SINAD (signal over noise and distortion) puts the NFB2 192 squarely in forth (worst) quarter of all DACs tested:

Audio-gd NFB2 192 kHz DAC SINAD Audio Measurements.png


Ironically it is not quite as bad as some of their newer designs.

Signal to noise ratio is good but falls way short of specifications:
Audio-gd NFB2 192 kHz DAC Dynamic Range Audio Measurements.png


You should be able to play 16 bit signal with the content dominating the noise level, not the DAC.

Linearity by our standards is poor:
Audio-gd NFB2 192 kHz DAC Linearity Audio Measurements.png


But again, good enough for CD/16 bit playback.

Jitter shows serious engineering issues but not of audible concern:
Audio-gd NFB2 192 kHz DAC Jitter Audio Measurements.png


Intermodulation distortion follows the same story:

Audio-gd NFB2 192 kHz DAC IMD Audio Measurements.png


The DX3 Pro at half the price has far lower noise and distortion.

I am going to stop here and put the energy toward other products to review.

Conclusions
I go into every review/measurement with a fresh slate. Alas, Audio-gd is one company whose measurement outcome can easily be predicted based on previous units tested. Instead of focusing on transparency and excellence in engineering execution, they follow audiophile myths into a ditch. Who says feedback is bad for the ear? Show me the controlled test of this DAC versus one using feedback where the Audio-gd comes out ahead. It doesn't and won't exist.

Fortunately audiophiles are blind to these types of distortions especially as SINAD approaches 80 dB. Hence the reason subjective, non-critical reviews don't hit on the deficiencies in NFB 2 192. Instead of going by sound waves, they substitute their expectation and prejudices in audio and think DACs like this, sound better. Being a false conclusion, that will wear off in later listening, sending them on upgrade path to yet another DAC. Oh well, I will stop the rant here :)

Needless to say, I can NOT recommend the Audio-gd NFB 2 192. There are plenty of other choices at lower costs that run circles around this unit.

----------------------
Questions, comments, critique, etc. are welcome.

In the last review, I mentioned that a work related accident had resulted in decapitation of one of my beloved pink panthers. Some of you wrote in, doubting the veracity of this story. Hopefully the review photo here shows that what I had said was no joke. While some kind donations were made to bring the poor little guy back to health, more money for after-care is needed for nurses and such. So please donate generously using:

Patreon: https://www.patreon.com/audiosciencereview), or
upgrading your membership here though Paypal (https://audiosciencereview.com/foru...eview-and-measurements.2164/page-3#post-59054).
 

garbulky

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#6
It's sad that they don't meet spec. I think Audio GD needs to be honest with their specifications. I think the industry as a whole are chasing these high performance dacs and so Audio Gd are inflating their specs to sell units. Leads to dishonesty all around. Also as you mentioned clearly there are much dacs with (much) better measurable performance.

However, I'd like to point out that if people don't hear the "issues" of the Audio GD in music listening then they aren't really issues are they? We have no evidence that their positive impressions "will wear off in later listening, sending them on upgrade path to yet another DAC." That's an assumption. How is it going to wear off? They aren't hearing it in the first place. Morel likely they won't hear the distortion and they'll keep using it without issue as a high quality dac.

If these dacs are meeting these (rather mundane) distortion specs, then people are not going to hear the distortion in music listening. Its snr is well below 80 and its highest distortion spur comes at a whopping -75 db below a full scale signal. How is anybody going to hear that when listening to their music? I know I can't.
 
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SEKLEM

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#7
If these dacs are meeting these distortion specs, then people are not going to hear the distortion in music listening. Its snr is well below 80 and its highest distortion spur comes at a whopping -75 db below a full scale signal. How is anybody going to hear that when listening to their music? I won't.
It’s not the performance or not meeting the specs I find most troubling, it’s the price. You can get subjectively better looking, objectively better made, and better performing DACs for less money.
 

Yuno

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#10
Morel likely they won't hear the distortion and they'll keep using it without issue as a high quality dac.
The only issue here is that it's not a high quality dac. People might get mislead into thinking it's a high quality dac due to their inability to tell the faults with their ears, while in reality they could get better dac with $100 or even their onboard. I think this is the main benefit of this website, giving people the ability to see actual, measurable performance, and helping them make conscious decision when purchasing.

@amirm Don't waste your valuable ressources on this name any longer, testing ban on audio-gd gear NOW !!! .....& stop killing the pink Panthers for nothing!!!
I was always curious about NFB 11.28, since it seems to be the least audiophooly out of audio-gd bunch, but considering everything we have seen, it's more likely to be the same than not.

Is there a single device from China, which is good for something?
This is strange comment considering where we are and how many of Amir's top recommendations belong to Chinese dacs. This website probably made Topping a lot of money.
 

Matias

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#12
@amirm Don't waste your valuable ressources on this name any longer, testing ban on audio-gd gear NOW !!! .....& stop killing the pink Panthers for nothing!!!
Agreed. So many interesting products waiting in queue and yet another bad measuring AudioGd product is reviewed? Amir, your time is too valuable for us to be used with them. Please take this not as a complaint but rather as a compliment! :)
 

amirm

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#13
We have no evidence that their positive impressions "will wear off in later listening, sending them on upgrade path to yet another DAC." That's an assumption. How is it going to wear off?
Placebo based effects work this way. Since they are based on one's mindset and not auditory input, when that mindset changes in the future, so does impression of said gear. You want to know why high-end audiophiles keep changing gear? This is the main reason.
 

amirm

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#14
Agreed. So many interesting products waiting in queue and yet another bad measuring AudioGd product is reviewed? Amir, your time is too valuable for us to be used with them. Please take this not as a complaint but rather as a compliment! :)
This was the second unit from the same member so I had to get it done. I also want to make sure we have broad enough set of reviews so people can't accuse us of testing just one "broken" unit.

Appreciate you all sentiments though. :)
 

amirm

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#15
Keep this pink panther on retainer for future reviews of Audio-GD products.
Well, we may be happy with him looking that way but he is not. He is complaining that he can't see himself in the mirror anymore!
 

Newk Yuler

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#18
This is another defunct model. It has little to no practical value versus other manufacturers' current products.

I believe all AGD products are worthy of ASR testing, especially current products because poor results will force them to up their game to remain competitive. That's how a self adjusting free market is suppose to work. AGD needs future tests of new products to prove them better worthy. I'll wager Kingwa understands and nothing will drive the message harder than a justified drop in sales. All we have to do is wait and watch.
 

fricc

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#19
I go into every review/measurement with a fresh slate. Alas, Audio-gd is one company whose measurement outcome can easily be predicted based on previous units tested. Instead of focusing on transparency and excellence in engineering execution, they follow audiophile myths into a ditch. Who says feedback is bad for the ear? Show me the controlled test of this DAC versus one using feedback where the Audio-gd comes out ahead. It doesn't and won't exist.

Fortunately audiophiles are blind to these types of distortions especially as SINAD approaches 80 dB. Hence the reason subjective, non-critical reviews don't hit on the deficiencies in NFB 2 192. Instead of going by sound waves, they substitute their expectation and prejudices in audio and think DACs like this, sound better. Being a false conclusion, that will wear off in later listening, sending them on upgrade path to yet another DAC. Oh well, I will stop the rant here :)
I usually very much agree with Amir's sane and reasonable conclusions about his excellent benchmarks, but in this particular circumstance I'd like to play devil's advocate for a moment, and reflect on the meaning of these measurements and on what they might or might not reveal.

Feedback is definitively a very well established circuit design technique, it works well by essentially subtracting the distortion as a difference of the input and the output signal. As I understand it, the criticism to using feedback comes from the fact that there is a significant enough delay in time between the input and the output, and depending on the circuit topology, the signal propagation speed and bandwidth, subtracting the difference signal might not be beneficial under all circumstances.

When measuring the circuit in a steady state situation, and where the test signal is relatively simple, the feedback circuit can virtually remove all distortion. My question is what happens on transient signals? What is the effect of the feedback when the correction does not reflect the current value of the input signal? By how much will it increase the actual distortion? Is it possible to estimate the feedback error or to measure it? Can we came up with a more "dynamic" measurement that can measure distortion under transient conditions?

Finally, it looks like the highest distortion peak stays below 75dB, THD+N is less than two parts part in ten thousand, a number that for a feedback free design is quite remarkable.

Thanks Amir for sparking this very interesting discussion subject, and thanks for having established this awesome site, this place is like is a breath of fresh HIFI air that I have been missing in the last 20 years.
- Fabio
 
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#20
>>a work related accident had resulted in decapitation of one of my beloved pink panthers<<

I'm calling OSHA!!!
 
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