This is a review of Gustard U12 which converts USB input to S/PDIF, Toslink, AES/EBU and I^2S. The U12 retails for $170 shipped from Amazon as of this writing. I will be comparing it to Audiophilleo 1 (about $500), Fiio E10K ($76) and Melodious-Audio MX-U8 ($269). Sadly my Berkeley Alpha USB is broken so I can't test against it even though it is at much higher price point.
Overview
The Gustard U12 is for people who have existing DACs and would like to add USB connectivity to it. The device has very good functionality with both consumer S/PDIF and AES/EBU professional digital outputs. It also has I^2S output for the few DACs that support it. For this testing, I focused on S/PDIF output only. Let me know if you want me to test other outputs.
I tested the unit without any drivers. Source was Roon player which reports the following formats:
So as is, support is limited to 192Khz, not 384KHz as advertised.
Reliability was excellent in the few hours of testing so no concern there.
A front panel display shows the sampling rate which I like to see. It is a simply LED 7-segment but useful to figure out if resampling is in the pipeline without one knowing.
The box is brushed aluminum and hefty example of that seeing how it includes the power supply inside. That also makes the unit quite hefty for the little box that it is. Overall, it is still a low-budget affair but at the high-end of that spectrum. And fit for the price charged.
Measurements
Since this device is a digital input, digital output, I started my test with an "eye pattern." I played 24-bit/48 Khz J-Test inside Roon as usual but then measured the time domain response of the S/PDIF stream:
The purpose of the eye pattern is to show much of safety margin we have in a serial communication stream to detect the "one and zeros." The red zone is the defined minimum by AES. This is for balanced output which I am not testing but gives you an idea. The Audiphilleo has a pretty strong output that is also clean, able to clearly get above the minimums standard. The Gustard U12 on the other hand, has anemic voltage output that was nearly half of Audiophilleo. As such longer cables could pose an issue for it.
Next we jump into our favorite test, J-Test in all cases driving the Topping D30 DAC. Here, I am zooming in both in frequency and amplitude to show the more interesting bits. First comparison is against the Audiophilleo:
As we see, the Audiophilleo easily outperforms the Gustard U12. I should mention that my Audiophilleo is a first generation device that I bought nearly 10 years ago. There is now second generation version of it. Despite that, it has no problem producing the best the Topping D30 can through its S/PDI input (which I should say, is worse than its USB input). So good design trumps age!
Next, let's go to the other spectrum, testing against the much cheaper DAC+Headphone Amp Fiio E10K:
Alright so something had to give for $79 and all this functionality and the Fiio E10K generates worse performance. Not an audible concern mind you but objectively so. Note that I am only using the digital S/PDIF output of Fiio E10 to drive the Topping D30. Not its DAC.
Rummaging through my bins, I find a loaned Melodious-Audio MX-U8 from member Mivera. It has identical functionality to Gustard U12 but in a bigger box.
In this zoomed display the Melodious-Audio MX-8 does better but when tested broadband (not shown) it had a spike that bothered me. So I say it is a toss up which one is engineered better.
So far we have been testing with a budget DAC. For the next set of tests, I used the Exasound E32 as the DAC (around $3,500).
As we see here, there is no difference at all how you drive the S/PDIF input on the Exasound E32. It excellently cleans up whatever ills may be on S/PDIF and renders the same excellent output. So if you have a high-quality DAC, there is no reason to anguish over how you are driving it.
Summary
The Gustard U-12 is an "OK" engineered product. I like its display and connectivity so I am not opposed to someone buying it. But it doesn't get my recommendation.
As usual, comments, questions, corrections are welcome.
The Gustard U12 is for people who have existing DACs and would like to add USB connectivity to it. The device has very good functionality with both consumer S/PDIF and AES/EBU professional digital outputs. It also has I^2S output for the few DACs that support it. For this testing, I focused on S/PDIF output only. Let me know if you want me to test other outputs.
I tested the unit without any drivers. Source was Roon player which reports the following formats:
So as is, support is limited to 192Khz, not 384KHz as advertised.
Reliability was excellent in the few hours of testing so no concern there.
A front panel display shows the sampling rate which I like to see. It is a simply LED 7-segment but useful to figure out if resampling is in the pipeline without one knowing.
The box is brushed aluminum and hefty example of that seeing how it includes the power supply inside. That also makes the unit quite hefty for the little box that it is. Overall, it is still a low-budget affair but at the high-end of that spectrum. And fit for the price charged.
Measurements
Since this device is a digital input, digital output, I started my test with an "eye pattern." I played 24-bit/48 Khz J-Test inside Roon as usual but then measured the time domain response of the S/PDIF stream:
The purpose of the eye pattern is to show much of safety margin we have in a serial communication stream to detect the "one and zeros." The red zone is the defined minimum by AES. This is for balanced output which I am not testing but gives you an idea. The Audiphilleo has a pretty strong output that is also clean, able to clearly get above the minimums standard. The Gustard U12 on the other hand, has anemic voltage output that was nearly half of Audiophilleo. As such longer cables could pose an issue for it.
Next we jump into our favorite test, J-Test in all cases driving the Topping D30 DAC. Here, I am zooming in both in frequency and amplitude to show the more interesting bits. First comparison is against the Audiophilleo:
As we see, the Audiophilleo easily outperforms the Gustard U12. I should mention that my Audiophilleo is a first generation device that I bought nearly 10 years ago. There is now second generation version of it. Despite that, it has no problem producing the best the Topping D30 can through its S/PDI input (which I should say, is worse than its USB input). So good design trumps age!
Next, let's go to the other spectrum, testing against the much cheaper DAC+Headphone Amp Fiio E10K:
Alright so something had to give for $79 and all this functionality and the Fiio E10K generates worse performance. Not an audible concern mind you but objectively so. Note that I am only using the digital S/PDIF output of Fiio E10 to drive the Topping D30. Not its DAC.
Rummaging through my bins, I find a loaned Melodious-Audio MX-U8 from member Mivera. It has identical functionality to Gustard U12 but in a bigger box.
In this zoomed display the Melodious-Audio MX-8 does better but when tested broadband (not shown) it had a spike that bothered me. So I say it is a toss up which one is engineered better.
So far we have been testing with a budget DAC. For the next set of tests, I used the Exasound E32 as the DAC (around $3,500).
As we see here, there is no difference at all how you drive the S/PDIF input on the Exasound E32. It excellently cleans up whatever ills may be on S/PDIF and renders the same excellent output. So if you have a high-quality DAC, there is no reason to anguish over how you are driving it.
Summary
The Gustard U-12 is an "OK" engineered product. I like its display and connectivity so I am not opposed to someone buying it. But it doesn't get my recommendation.
As usual, comments, questions, corrections are welcome.
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. I deleted that reference.
