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Review and Measurements of Gustard A20H DAC & AMP

invaderzim

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#23
There is no time to lose ... We need to buy as many Topping' devices as possible before they realize they are selling them too cheapy ... ;)
1) Buy them,
2) repackage in larger, fancier cases with heavy stuff inside, like power supplies
3) come up with a great name and back story on the new company
4) sell them for $800 - $2500
 

amirm

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#25
Your conclusion seems perfetly accurate to me - there's nothing wrong with this device except there are cheaper and slightly better performing alternatives.
Thanks. It is a good contrast to JDS Labs Atom. Many of these products cater to audiophile beliefs that the choice of components, plurality, weight, etc. contribute to better performance. In reality, something as "simple" as careful layout of a board results in much better performance than throwing millions of parts at a design.
 

amirm

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#26
Interesting test - I somehow missed it! So, that "bad stuff" would be IMD?
They are simple noise and distortion products generated by each tone. The reason you see more of them in higher frequencies is that all the earlier tones create them together. The more tones, the more "bad stuff" accumulates in later troughs between the tones.

And yes, they could also be intermodulation products.
 

Krunok

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#27
They are simple noise and distortion products generated by each tone. The reason you see more of them in higher frequencies is that all the earlier tones create them together. The more tones, the more "bad stuff" accumulates in later troughs between the tones.

And yes, they could also be intermodulation products.
That's why I used the term IMD. I'm looking at this test as a 32 tone IMD test so more and more tones, and thus more and more IM junk, are piling up at the right side of the spectrum. Is that a correct interpretation?
 

amirm

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#28
That's why I used the term IMD. I'm looking at this test as a 32 tone IMD test so more and more tones, and thus more and more IM junk, are piling up at the right side of the spectrum. Is that a correct interpretation?
Sure.
 

Krunok

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#29
The more I look at this test the more it is seems more relavant to me than THD+N test. IMO this test gives much more realistic picture thatn simple single tone THD test. I guess the resulting level of junk would be dependent of the signal level as well, right? Am I seeing well that the signal level you used was at app -16dB in this particular test?

I'm only thinking that you usually don't get such high levels at high frequencies so maybe a test where output level would decline with frequency would be more similar to real world music. What do you think?
 

amirm

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#30
I guess the resulting level of junk would be dependent of the signal level as well, right? Am I seeing well that the signal level you used was at app -16dB in this particular test?
No, the signal is at 0 dBFS:

1544724663205.png


The individual components that make up for it have to be at lower amplitude or their sum will be over zero.

Put another way, the DAC sees the time domain waveform, not its FFT analysis of its spectrum.

This is what the waveform looks like by the way (after capture):

1544724786747.png


As you see, it all looks random and jumbled up, showing the great value of FFT analysis to tell us what is really in the signal.
 

Krunok

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#31
No, the signal is at 0 dBFS:

View attachment 18770

The individual components that make up for it have to be at lower amplitude or their sum will be over zero.
Ah, sure - I forgot about that "little" detail. :D


Put another way, the DAC sees the time domain waveform, not its FFT analysis of its spectrum.
Sure, but isn't the waveform still a result of the frequencies and amplitudes of all the tones being played at the same time? I am merely thinking if you proportionally reduce the amplitude of the tones as the frequency is raising it would more resemble waveforms found in music. Or I'm wrong here?

I mean this: even when symphonic orchestra is playing fortissimo with all the instruments engaged amplitudes of the high frequencies won't be as high as the lower ones. I'm just thinking of the way to make this test more similar to real situations. :)
 

Louie

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#32
The A20H have both fixed or variable line output. I'm wondering which mode your measurements was made and if you can provide measurement of both to see if the variable control have additional noise? I appreciate your work to have measurement of more equipment than normally available. Thanks
 

garbulky

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#33
@amirm What do you think contributes it to not being loud enough? Also what contributed to the lack of bass? The unit puts out what seems to be more than enough power judging by measurements.
 

amirm

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#34
@amirm What do you think contributes it to not being loud enough?
Just lack of power when using unbalanced output. You can see that in the review graph:


As you see in red, Topping DX3 Pro has nearly twice as much power as Gustard A20H.
 

amirm

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#35
Also what contributed to the lack of bass? The unit puts out what seems to be more than enough power judging by measurements.
In my experience, you need tons of power for good bass performance. Our hearing sensitivity is poor in that region so you need the power to "feel" the sensation of bass. And yes, you do feel it in the cups and impact of the bass.

As for what is enough, the math people use never computes for me. I generally find that you need more power than the computation of sensitivity would tell you.

Alternatively, folks listen to lower levels than I do. I have set my standard to be sufficient to cover just about anyone. I don't listen at those levels all the time but for a few minutes, it is reasonable to be able to crank up the volume and enjoy powerful bass.

Finally, this is a function of the two reference headphones I test with: the HD-650 and HE-400i. With something like AKG K92, there is great power almost regardless of what drives them.
 
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#36
...Finally, this is a function of the two reference headphones I test with: the HD-650 and HE-400i. With something like AKG K92, there is great power almost regardless of what drives them.
Quick question: did you try the HD 650 with the balanced connection? I have volume issues with high-impedance headphones with balanced/SE combo amps if I'm not running balanced.
 

amirm

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#37
Quick question: did you try the HD 650 with the balanced connection?
No, I have yet to build the balanced cable for it. So much to do, so little time. :)
 
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#38
How's the crosstalk? I'd guess that it should do better in that area than DX3Pro. If it doesn't, the price is just too high.
 
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#40
A few months ago, I was about to buy the Gustard - luckily I became aware of the RME ADI DAC 2 here in the forum, I bought it and I'm still in love with it ;-)

Thanks to amrir!
 
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