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Review and Measurements of Audio-gd NFB-27.38 DAC and Headphone Amplifier

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amirm

amirm

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FYI, someone contacted their distributor and they posted a response: https://www.reddit.com/r/headphones/comments/86vbk7/audiogd_response_to_yesterdays_measurements/

Since they say some version was deleted, I am going to quote it here:

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submitted 3 hours ago * by Max_from_GermanyNFB 28.28 / LCD-2-C / HD 800 Anax V3+SDR

My initial post got deleted, I hope this modified version doesn't break the rules, if it does - mods please message me what part I need to change. I think this discussion is very relevant to this sub.

So I talked to Jos from Magna Hifi (European Audio-GD distributor) about this! post from yesterday, because I was worried that my 28.38 was effected.

Here is his response:

"The NFB27.37 was not a good product and has been removed quite fast.

We are working on a review for the NFB28.38 which we already got measurements from which shows a total different picture!

The reviewer is also really negative and not quite right in his measurements and conclusions.

I think the reviewer really missed the plot and the measurements are nice dressup to speak really bad about Audio-GD products in general. Lets be honest, the reviewer did not even get the Amanero working. Why couldn't he? This USB interface is used by so many manufactures but the reviewer was able to say even something negative about about the USB interface while this is not even designed by Audio-GD!! "For this testing, I was hoping to measure both USB and S/PDIF performance. Alas, I could not get Windows 10 Creator's edition to recognize Audio-gd as a proper sound device. It would recognize it on "hot plug" but then error out in the device manager saying it needs additional installation"

Secondly measurements of course are important but it doesn't tell you anything how a specific device sounds. This is not unrelated completely but you can't take conclusions from measurements. To keep it simple: Have ever ever measured an Valve amplifier or a phono record player? If you measure them all you will throw them all in the bin according to the reviewers opinion. This is of course bull shit. Valve amplifiers can sound really nice and so do phono record players! Same goes for Audio-GD, it is completely designed around a non feedback amplifier and they do not measure brilliant but they do sound awesome! You can put a Class-D amp next to an Audio-GD amp. The measurements are great of the Class D amp but the sound isn't. Usually its clean and boring sound.

I personally would not bother too much about reviews. I would just open my ears and listen. Its a wonderful headphone / preamp dac, really amazing sound!"

He also linked a couple of positive reviews about the NFB28.38 which I can't post without breaking rule 5.

Interested to hear what the people of this sub think of this.


----

So NFB27.37 was not a good product???
 

Wombat

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Looks so much like a Soekris on steroids, I have to wonder.
Hits about 16 bits linearity based on 6Moons review; certainly not 26 bits!
Why thousands of resistors? They don't get more accurate with quantity.
And oops!, the wrong kind of power transformers again. Toroids are just so transparent, you can use them as wideband audio output transformers.


Mmmmm. Toroids: https://www.soundstage.com/maxdb/maxdb071998.htm
 
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Blumlein 88

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This is too funny. They measure every single one, but it was never a good product. Now because of Amir they have to replace it. I wonder if it will have the same fairy tale graph with low distortion even though measured results are not important. :p
 
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Sal1950

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The measurements are great of the Class D amp but the sound isn't. Usually its clean and boring sound.
Now that's the last thing you would want, a clean sounding amp, right?
It needs to "create" a sound that is distorted but exciting. o_O
 

Wombat

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Now that's the last thing you would want, a clean sounding amp, right?
It needs to "create" a sound that is distorted but exciting. o_O

The problem is that subjective views vary so much. Maybe Cambridge Analytica can get some subjective consensus. It must be a marketing nightmare pandering to so many unknown preferences. But then, the individuals may not know their preferences until they are told what they are. o_O
 

Blumlein 88

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It occurs to me that the DAC in this review comes close to the performance of the $39 HDMI switcher/audio extractor I reviewed here.
https://www.audiosciencereview.com/...ewhd-prosumer-ultrahd-hdmi-3x1-switcher.1560/

The Audio-GD is a little bit better. But if you like its sound the ViewHD HDMI switcher has similar shortcomings in measurements at just a few db higher level. Poor man's Audio-GD. Just none of the cachet with the backstory and the big heavy chassis and all that.
 

Final

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Audio- GD has a point, from a fiscal point of view, saying that products that measures badly can sound wonderful. More than 50% of all audiophiles fall into the trap of trying to compensate for "sonic signatures" in one product with adding a product having reverse "sonic signatures". This is like compensating for a useless set of schock absorbers on your car with a new set of tires IMO. It does not work but the industry makes money.
 

SoniMax

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Wow. Greatly disappointed but reviews like this is are needed. I don't have this product but was interested in Audio G-D. I can only say that I hope they learn from this and improve their products.
 

Blumlein 88

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Wow. Greatly disappointed but reviews like this is are needed. I don't have this product but was interested in Audio G-D. I can only say that I hope they learn from this and improve their products.

I think the more workable response is you learn from this and pick better products than they make. They are everywhere to be had. Why bother with hucksters like Audio-GD who claim one thing and put out something entirely different?
 

Wombat

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I think the more workable response is you learn from this and pick better products than they make. They are everywhere to be had. Why bother with hucksters like Audio-GD who claim one thing and put out something entirely different?

Well, how does a consumer know in the absence of comparative factual information?
 

Blumlein 88

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Well, how does a consumer know in the absence of comparative factual information?
They of course don't. Mags like the old "Audio" did pretty thorough basic testing and would have ferreted out pretenders like Audio-GD easily. The fashion however is subjective reviewing and that measurements don't matter listening does. What Amir is doing here is very valuable. Because it isn't common. Stereophile is valuable in this sense though they make excuses to cover poor measurements. Soundstage.net is another resource. But there aren't many.

On the other hand for a few hundred bucks there is gear that would let you test other gear. While not laboratory grade measurement gear it will uncover ridiculous imposters like Audio-GD and Schiit.

At one time I remember McIntosh dealers having days you could bring in any gear and they would have people from McIntosh HQ test it. Maybe more clubs or canjams or audio shows need someone who will run quick basic tests on anything you bring in.

Amir has uncovered some affordable gear that measures very well. Hopefully the word spreads. The Topping gear in general is excellent and the word should be spread wide and far.
 

sssn

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On the other hand for a few hundred bucks there is gear that would let you test other gear. While not laboratory grade measurement gear it will uncover ridiculous imposters like Audio-GD and Schiit.

RMAA + decent Audio Interface comes to mind.

I measure all my DACs and headphone amps with RMAA and an EMU 0404 USB audio interface. It doesn't tell the whole story of course, but it's a decent pointer.
 

milokinni

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The best response might be for a disillusioned patron to let us measure another Audio Gd product...although I'll won't bet against it testing bad again.

Hi-fi News from the UK is another that presents audio measurements. The Absolute Sound on the other hand absolutely trashes objective measurements and blind listening tests.
 

SchwarzeWolke

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[...]

Secondly measurements of course are important but it doesn't tell you anything how a specific device sounds. This is not unrelated completely but you can't take conclusions from measurements. To keep it simple: Have ever ever measured an Valve amplifier or a phono record player? If you measure them all you will throw them all in the bin according to the reviewers opinion. This is of course bull shit. Valve amplifiers can sound really nice and so do phono record players! Same goes for Audio-GD, it is completely designed around a non feedback amplifier and they do not measure brilliant but they do sound awesome! You can put a Class-D amp next to an Audio-GD amp. The measurements are great of the Class D amp but the sound isn't. Usually its clean and boring sound.

I personally would not bother too much about reviews. I would just open my ears and listen. Its a wonderful headphone / preamp dac, really amazing sound!"
[....]
Audio- GD has a point, from a fiscal point of view, saying that products that measures badly can sound wonderful. More than 50% of all audiophiles fall into the trap of trying to compensate for "sonic signatures" in one product with adding a product having reverse "sonic signatures". This is like compensating for a useless set of schock absorbers on your car with a new set of tires IMO. It does not work but the industry makes money.

In my opinion, they're mixing things up. Amir has measured especially the DAC part of the NFB 27.38. For me, a DAC has one and only one role: Transform the zeros and ones into an analog signal and do that as faithfully as possible. What the amp does, is another story (and a long one...) and wasn't the main goal to begin with. The DAC performed poorly, especially in context of the high price you're paying.
 

bunkbail

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Wow. Greatly disappointed but reviews like this is are needed. I don't have this product but was interested in Audio G-D. I can only say that I hope they learn from this and improve their products.
Why would they learn anything? Their own coveted ACSS technology revolves around the idea of "better measurement doesn't mean better sound quality".
The ACSS [Audio-Gd Current Signal System] also is a non-feedback technology made with fully discrete amplifiers. Most people know the global feedback design can offer better specs in test measurements, and non-feedback can't do well in test measurements but can offer better sound for the human's ears. Here is a conflict of the classic circuits.
 

DonH56

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Paraphrased: "More distortion is better if it sounds more musical."

I'm trying to figure out from whence the whole "feedback is bad and global feedback is worse" point of view was spawned. It is clear most consumers do not understand feedback theory, nor should they need to, but the FUD around it is ridiculous. And ignores all the problems circuits without it can have, which is the reason it is used in the first place. OTOH it plays into other arguments, like the need for lengthy break-in, since without any sort of feedback to provide stability the performance will change as everything drifts during operation. Seems like another example where Marketing continually throws out terms new and old just to differentiate products, and plays up the changes (good or bad) as "new and improved", or maybe "old and improved".

Blah - Don
 

Blumlein 88

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As I recall it two things were touted in the old feedback is bad idea.

First is that a no feedback design might have 2nd and 3rd harmonic distortion. While a feedback design might have several more of the harmonics. Yes they were lower in level, but fewer harmonics is better than more harmonics as its more musical or so the story goes. I think this was a case of a little bit of marginally audible distortion gives character a clean amp doesn't have. In any case, as often in audiophile world such nonsense took hold strongly.

The other is from our old confusing friend transients in music. So confusing to people in so many ways. A high distortion device that needs high NFB to measure good didn't sound good. Since feedback required distortion at the output to travel back around to the input it measured good on steady state tones, but on transient music it meant the initial transient was heavily distorted before feedback could make the trip back to the input and fix it. So you couldn't measure it, but you clearly could hear it. A moderate distortion device with no feedback is therefore musically worlds better than a nasty device needing lost of feedback. Good measurements meant bad sound when feedback was involved.

And we have various related tales like local feedback or degenerative feedback is okay, but global feedback is not. etc etc.

Yes I know there are all sorts of things wrong with those two ideas, but it is what I recall being passed around by certain designers of boutique gear way back when. Somewhere along the way newbies never even heard those stories about why. It has simply become accepted wisdom that feedback is a negative (pun intended) and any device that could be made to work without feedback is inherently superior.

I rather enjoyed Bruno Putzey's article a few years back where he took the position the main problem with feedback is designers don't use enough of it.

The F-Word
https://linearaudio.net/sites/linearaudio.net/files/volume1bp.pdf
 
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FrantzM

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Paraphrased: "More distortion is better if it sounds more musical."

I'm trying to figure out from whence the whole "feedback is bad and global feedback is worse" point of view was spawned. It is clear most consumers do not understand feedback theory, nor should they need to, but the FUD around it is ridiculous. And ignores all the problems circuits without it can have, which is the reason it is used in the first place. OTOH it plays into other arguments, like the need for lengthy break-in, since without any sort of feedback to provide stability the performance will change as everything drifts during operation. Seems like another example where Marketing continually throws out terms new and old just to differentiate products, and plays up the changes (good or bad) as "new and improved", or maybe "old and improved".

Blah - Don

Trying to summon Ray Dunzl

http://hifisonix.com/wordpress/wp-content/uploads/2017/10/The-Theory-of-TIM-Matti-Otala.pdf

Abastract:
The existing theory of transient intermodulation distortion (TIM) is extended to cover the calculation of the duration of intermodulation bursts. It is shown that feedback values in excess of some 40 dB will cause large internal overshoots within the amplifier. The clipping of these overshoots due to the limited dynamic margins of the amplifier driver stages is shown to give rise to long periods during which the amplifier is in cut-off condition. The duration of these periods is calculated and the mathematical results are verified with digital and analogue simulation. Finally, the relationship of TIM, slew rate, and power bandwidth are discussed.

In excess of 40 dB causing troubles then no feedback must be good ... :D
 

Rene

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I rather enjoyed Bruno Putzey's article a few years back where he took the position the main problem with feedback is designers don't use enough of it.

The F-Word
https://linearaudio.net/sites/linearaudio.net/files/volume1bp.pdf

Bruno makes an excellent point: if you use too little feedback, it creates higher order harmonics, which sound more objectionable than simple second or third harmonics, and which may now be heard; whereas, if you use enough feedback, the higher harmonics will still be created but a so low a level that they don't matter.

The argument for moderate feedback is like the argument against FIR filters: FIR filters have pre-ringing, which is audible.
Well maybe, if you use a skimpy filter with too few taps. But use a long, well designed filter with true brick-wall response and very low in-band ripple and yes, the filter has a very long pre-ring but at so low a level that it will never be heard.
 

Rene

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If you look at the context of Otala's claim, it was warning against using too much feedback in very sluggish (low slew-rate) amplifiers, and then subjecting them to very fast rising transient information such as occurs with cartridge mis-tracking. The cure is simple enough: always low-pass limit the incoming information!
This is not an issue with today's well designed (for the most part) amplifiers playing CDs with their limited bandwidth.
 
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