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Review and Measurements of Gustard A20H DAC & AMP

RayDunzl

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#61
peace of technology
I'm always entertained seeing a new, possibly usable, and interesting phrase accidentally coined.
 

trl

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#63
Problem with such designs is they usually cost more and there is little they can offer to justify that, unless you can find pleasure in owning such "exotic" peace of technology.
We all know that inside opamps there are transistors, so not sure why call this design as "exotic". That's an old debate of discrete vs. integrated amplifiers.

Inside my Yamaha A-S701 there are no opamps in signal path, from INPUT to SPEAKERS (only Sub-out has opamps in LPF) and I like when there are companies out there able to build amplifiers by using their original design (this amp has all harmonics lower than -90dB, noise is non-existent @1m away from speakers - volume to the max w. no music playing). Same opamp free design is inside my Burson Conductor and this why I purchased both of the above amps, because I prefer to invest in R&D and not in copy-paste designs from manufacturer's datasheet, and an outer case made by a 3rd party company. I like new designs, innovation and originality...but that's just me probably. :)

However, I do love original designs opamp-based too, like:
- Chu-Moy (even Grado adopted the same schematic)
- Objective2 (first pot in-the-middle design and great way to create the output buffers)
- Per-Anders/sjostromaudio designs (he's mixing opamps with transistors, great output buffers, extremely low-noise PSUs, impressive designs done from scratch)
- Tom/Neurochrome designs (interesting how SMPS are followed by LPSU, original designs and interesting way to parallel output buffers, extremely good measurement numbers)
- THX789 (original output buffers, interesting protection, quite an original design).
 

k979khz

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#64
The (probably) official specs of the A20H, extracted and “validated” through google translate from a few different Chinese sources 2 years ago, before I bought my own unit :)

MAX POWER (RMS) balanced / unbalanced
16 ohm n/a / 1200mW
32 ohm 2400mW / 600mW
150 ohm 530mW / 133mW
300 ohm 266mW / 67mW (SENNHEISER HD650)
600 ohm 133mW / 33mW

When listening to the different outputs I would say that these figures really represents the superiority of the “balanced” output and I really think the unbalanced jack shouldn’t be used at all and probably should have been removed entirely by Gustard in the first place:) When driving HD650 (or HD800) from an Objective2 amp with A20H in DAC-mode it outperforms the unbalanced jack with some good margin. The difference is comparable to the DX3 Pro comparison in this review. BUT in balanced mode, I really feel it outshines the O2 in all regards by a huge margin, really night and day-difference making it impossible to appreciate the O2 with the HD650 anymore… :( And actually, I haven’t listened to any amplifier more suitable for driving the HD650/HD800 (/probably HD800S also), at least when trying to match it to my personal taste / hearing-curve etc. The only amps coming close are other balanced amps in higher price ranges (which I haven't been able to test for long enough time) or subjectively maybe an expensive DIY semi-tube amp (unbalanced) owned by a friend. For me I would describe the benefits of the A20H-balanced as more analogue / and somewhat “tubey” in its character but still with less distortion and absolutely black background. I suppose the completely discrete design is both responsible for the worse distortion measurements etc. but also for the pleasant analogue and somewhat Sennheiser-ish “long time listenable” sound-character. (I'm convinced that it should be possible to mimic analogue Vinyl/Tube-sound characteristics with some advanced distortion filters digitally applied... probably sounding better than "real" analogue sound :D ) But probably also because of the assumed benefits of “balanced” amping with supposedly better authority/control through push/pull-control of the drivers, and the stereo separation => benefitting the soundstage and depth of the HD650 and enhancing the stage of the HD800 further. Maybe also due to my balanced cables being many times more expensive than their stock unbalanced counterparts... Sadly it’s difficult to really A/B-test because of fast cable switching issues (I don’t want to destroy expensive cables by re-termination) and because normal hardware setups naturally give vastly different specs and characteristics between balanced/unbalanced outputs from the same amplifier.

I also own the HE400i (rev2) which I don’t like much (Focus Pad A and “the grill mode” turns them from bad to somewhat usable, but still not “reliable” as HD650.. some songs they handle well but others are kind of, a little bit... extremely bad presented :) ) But with those cans the benefits over the O2, my iFi iDSD nano or my AudioLab 6000A is not as apparent and mostly focused to the bass control. But I haven't really given it much time because I don’t use them normally.

With HD650 the vastly different sounding Sabre 9018-Dac of the AudioLab 6000A with its rather good integrated unbalanced headphone amp makes a cleaner but thinner, far more “non-analogue”, uninteresting and tiering impression compared to the Gustard, both with my HD650 and my KAM Near field active studio speakers. Also, the DAC of the iFi iDSD nano gives a very plain and boring sound whatever amp it drives and also my Odac is clearly inferior in the same regard compared to the A20H DAC.
 
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Jimmy

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#65

dancord

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#66
This is a review and detailed measurements of Gustard A20H DAC and headphone amplifier. It is on kind loan from a forum member. It retails for USD $850 on Amazon with free shipping (from China?). I am accelerating this review because it is on sale on massdrop for USD $700. Still not cheap but more reasonable.

For your extra money you get a much larger and beefier enclosure with a large LCD display:

I usually clean the units and touch them up in photoshop but in this case I choose to leave it alone so that you can see how well it shows smudges and scratches. Overall the enclosure is bland but OK.

Claim to fame of this unit is stepped attenuator implemented using a bunch of relays. The volume knob therefor is a rotary encoder telling the unit where to set the volume. And therein lies the main usability issue I found: if you rotate the knob quickly, it will change very slowly! This is of course the opposite of what you want. If I play a loud track, or after I have changed to a more sensitive headphone, I want to be able to rapidly turn the volume down. If you do that, the counter on the display changes very slowly (once a second?) as will the volume. You have to rotate the knob at a slow to medium rate to get it to change quickly.

Other than this, the menus are easy to navigate with up/down and knob to change setting.

For this testing, I am only using USB input. I tested both balanced XLR and unbalanced RCA for most of the tests. Let's see how she did.

Measurements
As usual we start with our dashboard view:

View attachment 18728

Our distortion measurement falls a bit short of published measurements. But if you look at the fine detail, you see that Gustard measurements are at -6 dBFS, not 0 dBFS as I test. Due to loudness compression, we tend to get a lot of music that reaches 0 dBFS so I like to see good performance at the limit. This puts the unit at the bottom of tier 2 of performance as far as distortion:

View attachment 18729

As you see on that graph, unbalanced produces about 3 dB lower performance.

Dialing down the level to -6 dBFS as Gustard has done, improves performance pushing SINAD to 108 dB using balanced connection.

We can see this issue immediately when we run our intermodulation distortion test versus level:
View attachment 18730

We see how both outputs start to rise in distortion levels as we approach 0 dBFS. This is likely due to the output buffer stage saturating.

As the A20H uses the AKM Dac chip, its performance almost mirrors that of Topping DX3Pro.

Jitter distortion and noise is a bit disappointing although not of audible consequence:
View attachment 18731

An ideal DAC would just show the main tone at 12 kHz and nothing else. Here, we see tons of jitter and distortion spikes in both balanced and unbalanced outputs.

Gustard A20H nails the linearity though showing that it produces correct voltages all the way down to -120 dB (20 bits):

View attachment 18732

That's the DAC performance. Let's switch to its headphone output and see what power we get with a 300 ohm dummy load using 1/4 inch unbalanced output:

View attachment 18734

This is a disappointing showing. The unit falls short of the performance of Topping DX3 Pro which retails for nearly 1/4 of it. It has both higher noise and distortion and less power.

Switching to 33 ohm load, we get this:
View attachment 18735

We see slightly better showing here but still nothing to justify paying more.

These values are far below the power specs from Gustard:

View attachment 18736

Of course they have no details as to how these power numbers were computed. Perhaps they are for "balanced" XLR headphone out? Let's test that at 50 ohm:

View attachment 18737

OK, we finally get decent amount of power. At 50 ohm, I am seeing nearly 1.7 watts which if one interpolates from the specs, seems correct.

Channel balance is excellent due to digital control of volume/stepped attenuator:
View attachment 18738

Likewise output impedance is a low 0.7 ohm which means it can drive just about any headphone without changing its frequency response:
View attachment 18739

Listening Tests:
As usual, I started testing using my Sennheiser HD-650 whose 300 ohm impedance let's us compare the objective results with subjective listening. Here, there simply was not enough power. I could dial the volume to max of "60" and while it was loud, it just wasn't enough. :) Base impact simply was not there. Switching to Topping DX3 Pro, there was an authority and headroom that was quite satisfying and lacking in Gustard A20H.

Next I switched to HifiMan HE-400i which with its 40 something impedance, attempting to match the objective to subjective again. Due to more available power at this low impedance, the situation was improved but I still preferred the Topping DX3 Pro. There was a bit more power in Topping and I got the impression of better resolution (could be placebo).

Conclusions
If you plan to use the normal 1/4 "single-ended" output of Gustard A20H, my advice is to save your money and get much cheaper products such as Topping DX3 Pro. You actually lose both performance and out of pocket money by using Gustard A20H.

Balanced mode has a lot more power but I can add a superb headphone amp such as JDS Labs Atom or Massdrop THX AAA 789 and be way, way ahead. It will be a two-box solution so if you want a tidy desk, and money is not a concern, then I guess the Gustard A20H fills that gap.

Overall, the A20H is not a bad unit and seems to have decent engineering. I just can't figure out what it does all that better to justify its premium.

-------------
As always, questions, comments, recommendations, etc. are welcome.

If you like this review, or even if you don't but wish for me to have lobster and steak for dinner tomorrow, please consider donating funds using:
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or upgrading your membership here though Paypal (https://audiosciencereview.com/foru...eview-and-measurements.2164/page-3#post-59054).
I own both the H2O and the A20H, reading what you wrote made me laugh a lot.
Every opinion must be respected, but when some devices are told as top class and opening the box we found something similar much more to a toy than a hi fi equipment...
Anyway keep on like this and good luck!
 

amirm

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#67
I own both the H2O and the A20H, reading what you wrote made me laugh a lot.
Meaning what?

Every opinion must be respected, but when some devices are told as top class and opening the box we found something similar much more to a toy than a hi fi equipment...
It doesn't matter what it looks like. It matters how it treats the audio signals you hear which is what the measurements are about. Once you know that, then you can pick on basis of looks, features, price. Audio marketing people love for you to just go by those non-audio factors. Don't fall prey to them....
 

dancord

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#68
Beg Your pardon,this is only an audiophile's opinion:
I'd like to stay quite and keeping on enjoying music, but, cannot agree with the method of the analysis at all ,infact, in spite of the abudance of measuraments,which frankly don't impress me much,..there is no enough space for serious listening tests.The better path is the "Santo Graal"of every constructor...but have never seen even middle class products ,built in a poor way, so a good hardware cannot be avoided.
What counts is music , the richness,the dynamics,the way make you thrill, getting close to hurt your ears, but finally,caressing, the emotions that can rise.. .Well...it has been at least 35 years I have been spending time and money in every kind of equipments,whith a lot of Joy and torment. but it is difficult to accept, that you don't listen to and neglect the balanced output...I REMENBER YOU THAT THIS DEVICE IS MEANT TO BE PLAYED IN BALANCED CONFIGURATION ,a territory unknown for your cheaper and miracoulous objects. THESE ARE NOT DETAILS!!Just like,discrete components,class A,high current.
If You only trust in meausuraments , can analyze a pair of tubes monoblocks and discover that a whatsoever masssdrop is better...take it in count,if You want give a good service.please.
Moreover,the A 20HGustard can act as a good simple transparent and neutral preamp ... balanced naturally.
Finally indeed,for this last and more other reasons ,the products are not comparable at all.
Best Regards
Dan
 

JohnYang1997

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#69
Beg Your pardon,this is only an audiophile's opinion:
I'd like to stay quite and keeping on enjoying music, but, cannot agree with the method of the analysis at all ,infact, in spite of the abudance of measuraments,which frankly don't impress me much,..there is no enough space for serious listening tests.The better path is the "Santo Graal"of every constructor...but have never seen even middle class products ,built in a poor way, so a good hardware cannot be avoided.
What counts is music , the richness,the dynamics,the way make you thrill, getting close to hurt your ears, but finally,caressing, the emotions that can rise.. .Well...it has been at least 35 years I have been spending time and money in every kind of equipments,whith a lot of Joy and torment. but it is difficult to accept, that you don't listen to and neglect the balanced output...I REMENBER YOU THAT THIS DEVICE IS MEANT TO BE PLAYED IN BALANCED CONFIGURATION ,a territory unknown for your cheaper and miracoulous objects. THESE ARE NOT DETAILS!!Just like,discrete components,class A,high current.
If You only trust in meausuraments , can analyze a pair of tubes monoblocks and discover that a whatsoever masssdrop is better...take it in count,if You want give a good service.please.
Moreover,the A 20HGustard can act as a good simple transparent and neutral preamp ... balanced naturally.
Finally indeed,for this last and more other reasons ,the products are not comparable at all.
Best Regards
Dan
1, Have you heard dx3pro? No?
2, Are you just trying to justifying all your purchases in the past?
3, Time is different now, there weren't products with this level of performance. Not available. But it's going far far away from what it was. It's getting really really good.
4, If you want to spend more money for same performance. Sure, go ahead, whatever makes you happy.
 

maxxevv

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#70
1, Have you heard dx3pro? No?
2, Are you just trying to justifying all your purchases in the past?
3, Time is different now, there weren't products with this level of performance. Not available. But it's going far far away from what it was. It's getting really really good.
4, If you want to spend more money for same performance. Sure, go ahead, whatever makes you happy.
Its what happens for many when cognitive dissonance kicks in ....
They just choose to stick to their affirmation biases instead.
 

JJB70

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#71
I would agree with the idea that what really matters is the music and the emotions created by the experience of listening to music (or spoken word etc). That is art. However, designing and manufacturing audio equipment is not art, it is science and engineering and measurement and analytical tools really can evaluate performance far more effectively and reliably than golden ears. The objection to measurement and objective evaluation from many audiophiles is I think a reaction to such techniques highlighting a lot of audio myths and snake oil for what they are.
 

JohnYang1997

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#72
I would agree with the idea that what really matters is the music and the emotions created by the experience of listening to music (or spoken word etc). That is art. However, designing and manufacturing audio equipment is not art, it is science and engineering and measurement and analytical tools really can evaluate performance far more effectively and reliably than golden ears. The objection to measurement and objective evaluation from many audiophiles is I think a reaction to such techniques highlighting a lot of audio myths and snake oil for what they are.
I agree on half. But subjective evaluation is the key of learning and progress. Objective measurements alone won't lead you to anywhere. Also more and more "snake oil" are objectively evaluated as beneficial. There are always reasons for those things. And audibility is not as easy as described before. Anything measurable should be considered audible. We should constantly measure and listen and progress.
 
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JJB70

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#73
I think we should be open minded to possibilities. If a subjective impression is validated by a double blind test then I think there is something to investigate. It may be that we need to reconsider what we measure or to develop new measurement methodologies. If, however, differences cannot be discerned in double blind tests and cannot be identified by measurement then I think it is spin and snake oil.
If there is a discernible and/or measurable difference validated by double blind testing then the discussion of whether it is significant or not, positive or not can be had. Not all discernible differences are significant (if people break out into a cold sweat with the stress of trying to discern allegedly "night and day" differences then that tells a story in itself).
My own entirely subjective opinion is that really well recorded great music just sucks me in and I don't really notice audio equipment, It's surprising how well great music shines through even on modest (some might say crappy) replay hardware.
 

amirm

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#74
I'd like to stay quite and keeping on enjoying music, but, cannot agree with the method of the analysis at all ,infact, in spite of the abudance of measuraments,which frankly don't impress me much,..there is no enough space for serious listening tests.
I have a cold right now and my ears are plugged. My instruments never catch a cold. :) If a device can't do justice to a simple sine wave, it can't do justice to complex music. My analyzer works a million times better in analyzing that sine wave than my ears can. It would be like asking your doctor to not use an X-ray machine and just look at you to tell you what is wrong with you. You don't tell him that, so don't tell me the same. :)
 

RayDunzl

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#75
My analyzer works a million times better in analyzing that sine wave than my ears can.

Audio Buddy brought his new DAC over last night to compare to my Benchmark.


Prep:

Levels set by ear (preamp trim) using mono pink noise - indistiguishable when switching between the two..​
Switching DACs was instant with a single click on the remote.​

Listening:

We thought the new DAC sounded quite different (much more spacious) than the Benchmark on much, but not all, material.​
Amazingly spacious.​
Sometimes spectacularly spacious.​
With the other guy switching, it was usually easy to tell which was playing, but not always, depending on the source material.​
We concluded the new DAC was creating some spatial "effect" that you got used to, but when switching back to the Benchmark, you just got used to it instead, and all was fine again.​
Made me think "Well, maybe the impression the Harbeth speakers gave me at the Audio Show was due to the electronics and not the speakers".​
So, it bothered me a bit. But not enough to want to run out and buy a new DAC (or speakers). I try not to be too easily excitable. It can be expensive.​
Then...​


Objective Test:

Identified a huge problem with the setup. The miniDSP, still in-circuit with the Benchmark but not the new DAC, expected to be simply passing digits based on selecting filter memory #4 (empty, and it was empty), had been left in a crossover mode from an experiment sometime back, so, instead of stereo, it was feeding the right channel to both the right and left speakers, and sending the left channel signal to the bit bucket.​
Mono source - no problem.​
Stereo source - sounded a little odd depending on the stereo separation (soft or hard panning) in the material. Whatever was in the left channel was missing, if it wasn't also in the right channel.​
Duh.

Fixed that and both DACs sounded the same. Indistiguishable on switching. The little click/discontinuity on switching makes you think maybe something is different, but no.

Ears. Brains. Expectations. Confusion. Reality.

Bleh.
 
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