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

[Mad_Economist]

I would love to see that so yes.

I'll send you an invite as soon as I can figure out how to PM/DM on this site. Here's the most recent provisional compensation data we have: https://cdn.discordapp.com/attachments/398789215644811265/414356632190058496/EARS_DF_APIMAVG.mic It was acquired by subtracting the difference between an average of several uncompensated FR sweeps on the EARS from an average of several diffuse field compensated FR sweeps on my B&K 4128C. Using it brought fairly close agreement between FR results on the EARS and 4128C with 3/4 headphones I had on hand to test at the time https://cdn.discordapp.com/attachments/398789215644811265/414356956808085514/unknown.png (same colour = same headphone, darker shades = EARS, lighter shades = HATS) though the HD800 remained problematic (as often it does).

 

[Wombat]

I just realized that the NFB in its name stands for no feedback. Is it possible to design a DAC without negative feedback but still measures as well as the Topping ones?

NFB means negative feedback in electronics and control systems.

 

[Blumlein 88]

NFB means negative feedback in electronics and control systems.

Not in bizzarro audiophile electronics poorly translated from Chinese. No Feed Back. NFB.

 

[SpeedyRodent]

Not surprised. This DAC probably is not defective. From my experience Audio GD stuff in general is pretty bad. Most of the DAC's I have heard from this company have audible differences that can be picked out. I usually cannot pick apart DAC's. The worst was a dac using NOS 1704 chips that had a combination of rolled off upper FR and distortion.

 

[rebbiputzmaker]

Not surprised. This DAC probably is not defective. From my experience Audio GD stuff in general is pretty bad. Most of the DAC's I have heard from this company have audible differences that can be picked out. I usually cannot pick apart DAC's. The worst was a dac using NOS 1704 chips that had a combination of rolled off upper FR and distortion.

Interesting. What is your reference?

 

[Blumlein 88]

Interesting. What is your reference?

I'm guessing flat response without distortion?

 

[rebbiputzmaker]

I'm guessing flat response without distortion?

Never heard of that brand. Can you provide a link?

Might be good to let others know what might be good to purchase. Hence the reason I posted the question.

 

[amirm]

Let's not get into debates in these review threads please.

 

[raideater]

Yeh, I can't make sense out of their specs/measurements.

I built a new fixture with just one channel measuring at full amplitude to see what it outputs from headphone amp. With my 33 ohm load it can only output 3.3 watts or so (about 10.5 volts). They don't have a spec for 33 ohm but they say at 50 ohm where power should be lower, it is supposed to output 8 watts. Maybe in balanced mode power doubles??? Even so, I still can't get their numbers.

I then went after their distortion measurements. They show this harmonic distortion test with similar model Audio Precision to what I have:

View attachment 11628

The only difference is that my load is 33 ohm and theirs is 30 but that should make it easier on them, not hard.

I can't imagine a no-feedback design doing as well as they show. Perhaps the above is a subsystem measurement seeing how it is analog to analog measurement and perhaps the design has evolved???

Hopefully they see these measurements and can respond.

From what I've seen, amps with an output impedance higher than 1 usually have a harder time driving lower impedance loads. In most cases, balanced is twice the power. Balanced mode is just 2 amps driving each channel separately.

Loving all the measurements by the way. They're the only thing keeping companies in check.

 

[Veri]

some of the worst measurements of any DAC/headphone amplifier I have tested so far.

Press F to pay respects.

I don't know what to believe anymore. Supposedly DS-based DAC should ace measurement tests, but seeing how bad this one goes I lose hope for Audio-gd R2R-based DACs ones, like my own R2R-11.

You can always send it in to Amir if he's okay with measuring another Audio-God I do wonder about the R2R Hype.

To Amir, thank you for verifying how this very pricy Audio-Gd sabre "Pro" Dac/amp measures, it's been a pleasure reading this thread!

 

[Deleted member 65]

" The loaned unit was purchased in China (?) and is an EU 240 unit powered by a transformer that converts 120 to 240."

Could the convertion from 240V/50Hz to 120V/60Hz have impacted measurements?

Edit: Or actually the other way round, 120 -> 240

 

[Final]

A very interesting review/measurement. Worse than expected and makes me really wonder about those R2R DACs. Never thought Audio GD gave any impression of quality but this was below my modest expectations.

I guess as so many DACs go unmeasured it is possible to get away with technically poor products. This site really does the quality orienteted audiophile great favours. So glad I found it.

Denafrips Terminator is a R2R DAC that looks impeccable, and according to the factory have the Specs to match. Would really have liked to see that one measured.

 

[AdrianG]

Good review armir. I know in sbaf they have hard feelings for audio gd, time ago they were collecting funds to buy gear to get mesured and tested among users, and they decided to buy one audio gd not sure what model but it was disastrous in sound and measurements.
http://www.superbestaudiofriends.org/index.php?threads/audio-gd-r2r-11.5348/

 

[Palladium]

For me, audio gd's talk about going to great lengths to avoid op amps in the signal path and any negative feedback were huge red flags.

Plays perfectly well into the audiophile siege mentality of how multi-billion electronic corps are ruining audio with their cheap soulless products.

 

[stunta]

Okay, so that is a different picture. Others have had similar measurements points to this being normal for the unit.

As the old saying in the software industry goes - "that's not a bug, its a feature!"

Just got permission to do so. There is a ton in there though so it may take a bit....

After these measurements, why do you have to subject yourself to this? I am starting to feel bad for you.

 

[SchwarzeWolke]

I really don't get it... If they're measuring themself, how is it possible that a product from Audio GD displays such a poor performance...

 

[Blumlein 88]

I really don't get it... If they're measuring themself, how is it possible that a product from Audio GD displays such a poor performance...

Maybe those measurements are a fairy tale.

 

[Dorian]

I really don't get it... If they're measuring themself, how is it possible that a product from Audio GD displays such a poor performance...

They're either lying or they have very poor QC. Anyway, about 3 years ago I purchased an Audio-gd preamp and I wasn't at all impressed by it; I guess this explains why... (not to mention the clicks and pops when changing the frequency rate of the files in the audioplayer).

Many thanks for your effort Amirm!

 

[amirm]

After these measurements, why do you have to subject yourself to this? I am starting to feel bad for you.

Because there is some educational value in how these devices work and are designed. That said, yes, it would be pure torture to try to reverse engineer this device. So I might just post some pictures and a few words and leave it at that.

 

[Rene]

Denafrips Terminator is a R2R DAC that looks impeccable, and according to the factory have the Specs to match. Would really have liked to see that one measured.

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.