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Review and Measurements of Gustard DAC-X26

amirm

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The reason I asked the question perhaps is obvious to you but not some other readers. If you plan on purchasing doc and using it as a preamp you have to realize a few things. Power amps typically require 1V RMS to achieve full power on the output. Considering the typical amplifier gain and modern speaker sensitivity one would never use this thing with volume setting near 0dB (or -2dB). It would be great to see measurements in 10dB increments from -90dB up to 0db in 10dB steps. I realize it is your time and extra work. Though -90 and -45 (half way) would be sufficient to satisfy my curiousity. ;)
The IMD measurements show those steps. A THD+N curve would be similar.
 

amirm

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When I see AP measurements and that are interesting I always have some questions. I hope you don't treat them as me trying to criticize any work that you do. When you perform DAC measurements what load are you using? 100kOm? If so have you considered using 300 or 600 Ohm instead and plotting them side by side with 100kOhm?
If you look at the the bottom of the dashboard, you see the test conditions such as what you ask:

1552520921654.png


For unbalanced, it is 100 K ohm. For balanced it is naturally double that per above.

This is for DAC testing. The dashboard for headphone amps does use 600 ohm.

I don't think it makes much sense to test a DAC output at 300 or 600 ohm. I know stereophile does that but I don't see a common case where the target device has such a low input impedance.
 
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If you look at the the bottom of the dashboard, you see the test conditions such as what you ask:

View attachment 23552

For unbalanced, it is 100 K ohm. For balanced it is naturally double that per above.

This is for DAC testing. The dashboard for headphone amps does use 600 ohm.

I don't think it makes much sense to test a DAC output at 300 or 600 ohm. I know stereophile does that but I don't see a common case where the target device has such a low input impedance.
Thanks. I have seen that but I wasn't sure if you used 100k/200k for all tests. You know you would be surprised what one may find in some cases. Passive preamp I have mentioned previously is not the only example. About a year ago I had to deal with AUX input port in my wife's BMW. The input impedance at 100 and 1000 Hz was around 1.1kOhm and at 10kHz it was at 180 Ohm! The Android device I have installed had 1kOhm series resistor in the output. To make matters worth Aux port in BMW has 2 caps in parallel with the signal... You can imagine what frequency response looked like. Similarly it had no bass response as someone created the RC filter with incorrect selection of nominal values. Though it was relatively easy fix... This is a mass produced device.
So one more request to add to the "suggestion box" is to measure output impedance of the DAC.
 

amirm

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No they don't! You vary the stimulus amplitude on digital generator instead of attenuating the amplitude using builtin volume control.
IMD is that way. And any THD graph I run will be the same.
 
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I am not sure. Their marking material just says it goes from 0 to 90 and is digital in nature.
I sent an email to Gustard, which also mentioned this question.
They said that the X26's volume control is based on the built-in digital volume of the ES9038Pro.
By the way, this is their official email address. I found it on Head-Fi.
[email protected]
 

Music1969

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Hi @amirm

In which of your typical measurements would you expect to best see any USB 8kHz PHY microframe packet noise?

Have Gustard done a good enough job that it doesn't even show up in any of your measurements, i.e. it's below the noise floor of your APx555?
 

Newk Yuler

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Is it fair to assume the Gustard X26 is an example of a proven, very well designed modern DAC that would gain no benefit from something like an Empirical Audio device? I'm not trying to open a fresh can of worms. I know there is at least one camp here that will say there's no use for EA in many to any case. Please understand that I'm from the side who will testify good experience with EA products over many years. I'm wondering, short of paying just to prove it to myself if mid-range DAC products have evolved to a point that there is nothing more to be gained from external digital refining devices. I suppose I'm asking for opinions from members who have relied on Steve Nugent's products perhaps until DACs like the Gustard X26 have become available. I'm aware there are subjective reviews of DACs at higher price points (higher design sophistication and quality components) that users claim to have tried and state EA products don't improve. Could it be because more sophisticated tech has trickled down to DACs at a lower price point? Has Amir tested much more expensive DAC products that measure extraordinarily well for reference?

BTW, I'm waiting on the Yulong DA10 profile then I'm going to make a short list of prospects in that price range, although I may choose to leave it be. Seems there's a new niche of products trying to compete with the RME. A very interesting niche, IMO.
 

amirm

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Hi @amirm

In which of your typical measurements would you expect to best see any USB 8kHz PHY microframe packet noise?
It shows up in the jitter test. If you look there, you see a spike at 8 Khz.

 

amirm

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Is it fair to assume the Gustard X26 is an example of a proven, very well designed modern DAC that would gain no benefit from something like an Empirical Audio device?
I will test them together when it arrives. For now, USB is the universal input as far as I am concerned and there, Empirical doesn't offer anything.
 

Newk Yuler

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I will test them together when it arrives. For now, USB is the universal input as far as I am concerned and there, Empirical doesn't offer anything.
Not sure the Synchro Mesh is the right product to compare to the USB. The result will surely be interesting but the Off Ramp is the USB product with much more sophistication including S/PDIF by BNC and balanced connections. Also I2S by HDMI and RJ45, although the HDMI pinout is not compatible with the Gustard (according to Shenzhenaudio). An optioned Off Ramp has Hynes regulators on important circuits. The Synchro Mesh maybe none until it's powered by the Dynamo. The Off Ramp is bit perfect, the Synchro Mesh not. I expect Steve asked you to test the Synchro Mesh because it's his most popular product and he's getting ready to introduce a new Off Ramp making a test of the OR5 nearly a waste of everybody's time.
 

Veri

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Not sure the Synchro Mesh is the right product to compare to the USB. The result will surely be interesting but the Off Ramp is the USB product with much more sophistication including S/PDIF by BNC and balanced connections. Also I2S by HDMI and RJ45, although the HDMI pinout is not compatible with the Gustard (according to Shenzhenaudio). An optioned Off Ramp has Hynes regulators on important circuits. The Synchro Mesh maybe none until it's powered by the Dynamo. The Off Ramp is bit perfect, the Synchro Mesh not. I expect Steve asked you to test the Synchro Mesh because it's his most popular product and he's getting ready to introduce a new Off Ramp making a test of the OR5 nearly a waste of everybody's time.
I think Amir was getting the whole mesh and dynamo stack though.
 

Krunok

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I will test them together when it arrives. For now, USB is the universal input as far as I am concerned and there, Empirical doesn't offer anything.
But I'm sure he would offer platinum USB cables in the near future which will sound much better in terms of reduced smearing than cheap ordinary ones :D
 

pkane

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Not sure the Synchro Mesh is the right product to compare to the USB. The result will surely be interesting but the Off Ramp is the USB product with much more sophistication including S/PDIF by BNC and balanced connections. Also I2S by HDMI and RJ45, although the HDMI pinout is not compatible with the Gustard (according to Shenzhenaudio). An optioned Off Ramp has Hynes regulators on important circuits. The Synchro Mesh maybe none until it's powered by the Dynamo. The Off Ramp is bit perfect, the Synchro Mesh not. I expect Steve asked you to test the Synchro Mesh because it's his most popular product and he's getting ready to introduce a new Off Ramp making a test of the OR5 nearly a waste of everybody's time.
Considering the asynchronous nature of USB input, I see no reason for external reclockers of any kind -- the data is already reclocked by the USB receiver. That's been my experience with properly implemented modern DACs, both, in measurements and in listening tests.

Amir measured Gustard X26 here with his AP, and I measured an older Gustard X20Pro (with much, much more modest equipment). The result puts jitter below -135dB mark with 0dBFS signal. This is far below audibility, even if you play music at the loudest setting that doesn't destroy your ears.
1552650649028.png
 
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Can you fix the volume on this DAC, like you can on the VMV D1? Also can you run either synced or asynchronous in the USB option menu?

The new ESS USB jitter control looks "worse" than the XMOS designs (XU208/216), What benefit did ESS add by creating it's own USB chip? I wonder if the ess usb chip is cheaper to purchase by gustard

I would love to see testing off the I2S (HDMI) input if possible. I have always wondered if that is a improved interface over toslink or usb.

Also where is the gustard actual website, for drivers and manuals?
 
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Thanks for the review.

I own a X-20 Pro with USB input and after one day of listening I retired my Benchmark DAC-2 that was twice the price. This was a little under two years ago, the unit was purchased blind (no reviews were up at the time) from Shenzen Audio as well and their service has been nothing short of exceptional on either that or the Sanskrit 10th and the DX3 Pro I picked up last year. I have been considering an upgrade to the X-26 as well later this year, if my purse allows it.

I had not seen the review of the X-20 before I purchased and it took some time for the measurements to be made available, I bought it on the strength of design (that I could see and a gut feeling). Seems like it was a good decision at the time - and the X26 looks like more of the same. I would really like to see what happens with sharper filters, IME the measurements and the listening experience are both better with less hf hash in the output. The new I/V stage looks a treat - obviously with the massive output current of the 9038Pro they needed a new design from the ground up.

I like that they separate the clock and run it over a dedicated RF path. I believe this to be one of the keys to the Gustard's performance, as clocks can really mess up power supply performance for all other circuits. I'm hoping the front-end is good - the X-20 was a more lazy DSP by comparison and lacked the sophistication of something like the Benchmark, which has a much better thought through design. Looks like Gustard dipped into the ESS goodie bag for the USB solution - which is a refreshing change from the XMOS bandwagon though it's not a proven part yet. Truth be told it's the one thing - apart from $$ - that's holding me back a bit.
 

yummy

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amir, they have this new preamp coming you should contact them to send you one to mess with, heard it was pretty high performance
 

yummy

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the rep only told me new preamp without model name, plus a entry level DAC x10

guess the name would be h30
 
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