Audio-GD NFB-11.38 Performance Edition Measurements
Hi folks,
Here is my review, measurements-based, of the Audio-GD NFB-11.38 Performance Edition. This unit has been kindly loaned to me by @Audiophonics and costs 469€ tax incl. It is the last iteration to date of the NFB-11 DAC & headphones amp combo, which is the entry-level from the Chinese manufacturer, that has known a lot of hype on forums for the last 7 or 8 years.
Now that measurements are getting more and more popular, the brand is considered as kind of controversial. Some objective reviews of Audio-GD products effectively revealed notoriously bad performance... Main issues were not only their terrible results on the bench, but the fact that the manufacturer claimed measurements and specs impossible to replicate. Nowadays, the name Audio-GD itself is becoming somehow polarizing, leading to irrational feedbacks from either haters or fanboys. I personally do not pay attention to these, as I should focus on objective analysis only, and I will, no matter the brand.
"Performance Edition", right? I'll put its name to the test...
The front panel is the same as any others NFB-11. There are old school switches for inputs, Gain and outputs. The latter is useless (it does not work for variable/fixed) out of the box. No. You have to first open the unit and move a jumper inside to get it working... which, I'm sorry, is stupid. Volume control is analog, which differ quite significantly from the vast majority of modern DACs that are using digital attenuation.
The unit has its own integrated PSU. You got the regular USB/Toslink/Coax trio, with one unbalanced output. I have to admit that I liked the excellent quality of all connectors, each socket having a great grip/fit with cables.
Audio-GD claims 2.5V fixed output, which is not what you get using Low Gain (barely 1Vrms or so). Switching to High Gain gives you something much closer to specs, and this is the main setting tested for this review (with Cosmos set @2.7Vrms input). I also chose Toslink as the main input for measurements to come, and this, for a good reason. More on that later...
I would have liked to test different filters, but just like the fixed/variable setting, you have to put/pull jumpers inside... Even better, pins are inaccessible to me, being below the USB board. Am I supposed to remove the latter first? Since this is not my unit, that isn't going to happen.
Here is my review, measurements-based, of the Audio-GD NFB-11.38 Performance Edition. This unit has been kindly loaned to me by @Audiophonics and costs 469€ tax incl. It is the last iteration to date of the NFB-11 DAC & headphones amp combo, which is the entry-level from the Chinese manufacturer, that has known a lot of hype on forums for the last 7 or 8 years.
Now that measurements are getting more and more popular, the brand is considered as kind of controversial. Some objective reviews of Audio-GD products effectively revealed notoriously bad performance... Main issues were not only their terrible results on the bench, but the fact that the manufacturer claimed measurements and specs impossible to replicate. Nowadays, the name Audio-GD itself is becoming somehow polarizing, leading to irrational feedbacks from either haters or fanboys. I personally do not pay attention to these, as I should focus on objective analysis only, and I will, no matter the brand.
"Performance Edition", right? I'll put its name to the test...
The front panel is the same as any others NFB-11. There are old school switches for inputs, Gain and outputs. The latter is useless (it does not work for variable/fixed) out of the box. No. You have to first open the unit and move a jumper inside to get it working... which, I'm sorry, is stupid. Volume control is analog, which differ quite significantly from the vast majority of modern DACs that are using digital attenuation.
The unit has its own integrated PSU. You got the regular USB/Toslink/Coax trio, with one unbalanced output. I have to admit that I liked the excellent quality of all connectors, each socket having a great grip/fit with cables.
Audio-GD claims 2.5V fixed output, which is not what you get using Low Gain (barely 1Vrms or so). Switching to High Gain gives you something much closer to specs, and this is the main setting tested for this review (with Cosmos set @2.7Vrms input). I also chose Toslink as the main input for measurements to come, and this, for a good reason. More on that later...
I would have liked to test different filters, but just like the fixed/variable setting, you have to put/pull jumpers inside... Even better, pins are inaccessible to me, being below the USB board. Am I supposed to remove the latter first? Since this is not my unit, that isn't going to happen.
Measurements
Disclaimer: Measurements you are about to see are not intended to be as precise or extensive than what you get from a 30k€ AP. There is obviously both hardware and software limitations here, so not quite apples to apples comparison with Amir's testing. For example, I estimated SINAD (AKA THD+N) to be usually 5 to 6dB worse with my measurements rig, when compared to ASR reviews of the exact same products. Still, this data is enough to have a pretty good idea if the gear is bad or not, stellar, broken, or sub-par...
- ADC : E1DA Cosmos (Grade B), set to 2.7Vrms input. Minimum phase filter.
- Software : RMAA 6.4.5 PRO and Multitone Loopback Analyzer 1.0.15.
- Method : 8 runs for each test, then I choose the closest to the average. All regular tests are running 24bits / 44.1Khz. For this review, I introduced a new Jitter test (48Khz, 1-24Khz bandwidth, 16 averages, 262k FFT, thanks @pkane) and improved the Multitone one (Now 64 tones, 192Khz, 20Hz-22Khz bandwidth, 10 averages, 262K FFT).
- Audio-GD NFB-11.38 : Optical input, 2.5Vrms fixed output (High Gain) for main results, unless specified otherwise.
RMAA Summary
Test | Results | Rating |
Frequency response (from 40 Hz to 15 kHz), dB | -0.05, -0.08 | Excellent |
Noise level, dB (A) | -105.5 | Very Good |
Dynamic range, dB (A) | 105.5 | Very Good |
THD, % | 0.00449 | Good |
THD + Noise, dB (A) | -84.4 | Average |
IMD + Noise, % | 0.00485 | Good |
Stereo crosstalk, dB | -74.1 | Average |
IMD at 10 kHz, % | 0.00455 | Good |
For this review, I chose to throw the grading scale from RMAA away, since it is clearly outdated and way too gentle to properly qualify this kind of performance. So I decided to adjust the rating to my own appreciation, based on many DACs I already measured. On this matter, I have to admit that I expected much worse numbers. Anyway, let's have a look at graphs in details:
THD + Noise (at -3 dB FS)
Left | Right | |
THD, % | 0.00611 | 0.00287 |
THD + Noise, % | 0.00628 | 0.00322 |
THD + Noise (A-weighted), % | 0.00806 | 0.00395 |
Frequency response
Left | Right | |
From 20 Hz to 20 kHz, dB | -0.11, +0.02 | -0.18, -0.04 |
From 40 Hz to 15 kHz, dB | -0.02, +0.02 | -0.08, -0.05 |
Noise level
Left | Right | |
RMS power, dB | -104.4 | -104.4 |
RMS power (A-weighted), dB | -105.5 | -105.5 |
Peak level, dB FS | -81.5 | -80.0 |
DC offset, % | -0.0 | +0.0 |
Dynamic range
Left | Right | |
Dynamic range, dB | +104.3 | +104.4 |
Dynamic range (A-weighted), dB | +105.4 | +105.6 |
DC offset, % | -0.00 | +0.00 |
Intermodulation distortion (swept tones)
Left | Right | |
IMD + Noise at 5000 Hz, | 0.00717 | 0.00403 |
IMD + Noise at 10000 Hz, | 0.00495 | 0.00314 |
IMD + Noise at 15000 Hz, | 0.00490 | 0.00314 |
Intermodulation distortion
Left | Right | |
IMD + Noise, % | 0.00619 | 0.00350 |
IMD + Noise (A-weighted), % | 0.00381 | 0.00228 |
Stereo crosstalk
Left | Right | |
Crosstalk at 100 Hz, dB | -73 | -73 |
Crosstalk at 1000 Hz, dB | -73 | -73 |
Crosstalk at 10000 Hz, dB | -73 | -73 |
Surprisingly, overall performance navigates between "good", acceptable and below average, depending on what it is measured. There is nothing here that should be considered as a serious audible concern, worst being THD+N that is dominated by second harmonic. On the other hand, it is miles behind what we should expect from a decent ES9038 PRO implementation.
By the way, I noticed that the unit got quite warm after dozens of minutes. I wondered if this could affect the performance somehow. I launched these two runs, one few seconds after switching it on, the second after running for 4 hours:
Test | Just turned on | 4 hours warm-up |
Frequency response (from 40 Hz to 15 kHz), dB | -0.05, -0.08 | -0.05, -0.08 |
Noise level, dB (A) | -105.4 | -105.5 |
Dynamic range, dB (A) | 105.5 | 105.4 |
THD, % | 0.00449 | 0.00457 |
IMD + Noise, % | 0.00485 | 0.00495 |
Stereo crosstalk, dB | -74.0 | -71.9 |
Almost no change, except for crosstalk.
Now that we have seen the best case scenario, here comes trouble:
USB VS Coaxial VS Optical
Test | USB | Coaxial | Optical |
Frequency response (from 40 Hz to 15 kHz), dB | +0.02, -0.02 | -0.05, -0.08 | -0.05, -0.08 |
Noise level, dB (A) | -93.6 | -94.1 | -105.5 |
Dynamic range, dB (A) | 93.6 | 94.1 | 105.5 |
THD, % | 0.00451 | 0.00444 | 0.00449 |
IMD + Noise, % | 0.00870 | 0.00911 | 0.00485 |
Stereo crosstalk, dB | -80.5 | -78.6 | -74.1 |
Noise
As said earlier, I chose Optical as the main input to test, mainly because others showed significantly worse results. The main issue appears to be noise for both USB and Coaxial, which is very unusual for the latter. It is literally the first time I observe so many disparities between the two S/PDIF inputs. In fact, I often do not even feel the need to measure both, as they supposed to perform 99% the same in every run... Not in that case. Far from it, to be honest. USB performance is a real shame, when you know Amanero boards alone are very expensive already (like ≈50$ if I'm not mistaken). There is really something broken here. Is it related to either poor implementation and design or lack of quality control? I honestly do not care. This is a brand-new unit that anybody could have bought, and it shows serious flaws out of the box. Period.
Switching back to the toslink input, I tested the preamp at several volumes, relative to different input settings (about -1dBFS for each voltage) of my Cosmos :
Switching back to the toslink input, I tested the preamp at several volumes, relative to different input settings (about -1dBFS for each voltage) of my Cosmos :
Preamp
Test | 3.6Vrms input (Max vol LG) | 4.5Vrms input (HG) | 6.7Vrms input (HG) | 7.6Vrms input (HG) | 8.5Vrms input (Max vol HG) |
Frequency response (from 40 Hz to 15 kHz), dB | +0.07, -0.23 | +0.32, +0.21 | +0.19, -0.01 | +0.14, -0.12 | +0.09, -0.22 |
Noise level, dB (A) | -95.5 | -104.2 | -104.3 | -104.1 | -104.0 |
Dynamic range, dB (A) | 95.5 | 104.2 | 104.4 | 104.2 | 104.1 |
THD, % | 0.00262 | 0.00216 | 0.00528 | 0.00862 | 0.012 |
IMD + Noise, % | 0.00586 | 0.00282 | 0.00527 | 0.00827 | 0.011 |
Stereo crosstalk, dB | -75.0 | -75.6 | -77.9 | -78.4 | -78.7 |
Results are surprisingly consistent between the very different levels when looking at dynamic range and noise ! Only THD goes higher along with output. You can get up to almost 9Vrms, which is crazy high for single ended. There is still a bit of channel mismatch at some levels, between 0-0.1dB and 0.3dB in worst cases (at 4.5Vrms). To me, the NFB-11.38 could act as a fairly capable preamp:
I cannot test headphones output extensively without a proper load board. Still, I measured a few captures at fixed voltages :
Headphones amp
Test | Headphone out Low Gain at 1.7Vrms | Headphone out High Gain at 6.7Vrms |
Frequency response (from 40 Hz to 15 kHz), dB | +0.09, -0.19 | +0.13, -0.15 |
Noise level, dB (A) | -96.6 | -104.6 |
Dynamic range, dB (A) | 96.7 | 104.7 |
THD, % | 0.00248 | 0.010 |
IMD + Noise, % | 0.00586 | 0.00963 |
Stereo crosstalk, dB | -85.9 | -87.0 |
After checking back my data, the 3rd harmonic peak is also there at 6.7Vrms with the RCA line out, so finally not introduced by the headphones amp itself. I am pleased to see that the headlamp is performing almost on par with line outs, which is very uncommon, in a good way !
Jitter tests
Optical
USB
Coaxial
Optical did not show any problem when it comes to jitter. USB on the other hand acted really crazy, with one run out of three showing really weird shapes. You see one of them on the graph. Coaxial at last was more consistent, but pretty bad in just every way.
Multitone 64
Optical
Coaxial
USB
When looking at multitone, toslink, again, performed the best, yet with some unremarkable score of 86dB TD+N. Needless to say, USB and Coaxial repeated their quite bad performance like in any others tests...
Bonus
Since I had no choice but to open the unit to get it working, you get a free teardown.
Conclusions
It is clear that the Audio-GD NFB-11.38 "Performance Edition" (I insist on quotation marks) does not deserve its so-called appellation. I could not imagine how mediocre would have been the non-performance NFB-11.38 at this point. I have been told that this series has been designed by Audio-GD to measure well, as opposite to their R2R DACs... Well, it is quite a failure in that regard.
Maybe all of this would only be related to the discrete Non-FeedBack architecture, but that is not an excuse when you get two digital inputs out of three that are flawed that way. Yes, I have no doubt that these second and third harmonics are here on purpose, but do not tell me these messed-up noise and jitter are any kind of intentional. On the other hand, assuming you would need optical input only, what do you get, really ? In fairness : near-good-enough DAC, at least suitable for 16 bits content, with both powerful headphones amp and strong preamp, that all perform cohesively with each others. Last chance for the manufacturer's redemption could be the AS-1, supposedly properly engineered with common op amps and balanced output...
Anyway, my sincere thanks again to @Audiophonics for sending me this product, even when knowing the risk of not so great results !
Flanker rating: Meh
Maybe all of this would only be related to the discrete Non-FeedBack architecture, but that is not an excuse when you get two digital inputs out of three that are flawed that way. Yes, I have no doubt that these second and third harmonics are here on purpose, but do not tell me these messed-up noise and jitter are any kind of intentional. On the other hand, assuming you would need optical input only, what do you get, really ? In fairness : near-good-enough DAC, at least suitable for 16 bits content, with both powerful headphones amp and strong preamp, that all perform cohesively with each others. Last chance for the manufacturer's redemption could be the AS-1, supposedly properly engineered with common op amps and balanced output...
Anyway, my sincere thanks again to @Audiophonics for sending me this product, even when knowing the risk of not so great results !
Flanker rating: Meh
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