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Gustard U12 USB Interface 8 Core XMOS chip

Discussion in 'Computer Audio' started by rb2013, Sep 27, 2014.
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  1. ginetto61
    Hi very difficult question.  I can only say that i have both and i think the Melodious is better.  I should keep just one i would keep the Melodious, more expensive.
    IMHO they have both margins of improvements, especially regarding mains filtering.
    Could you tell me a little more about this cable ? have you bought it or made it yourself ?
    I see that a usb cable has: screen, data + and - , Vcc and ground.    In your cable only the data wires are connected or also the screen ? 
    Unfortunately many usb dacs still rely on power from the pc to work.  While even my cat knows how dirty is pc power.
    With some dirty and other very very dirty ... and also weak in terms of availbale current.
    This is quite bizzarre for me. It should be one of the main requirements when designig a usb interface.
    as i said you should try and listen.   If you test the U12 you should use also a usb power supply (like the Wyrd) because the unit does not provide usb isolation by itself ... [​IMG]
    and i would use the AES/EBU out from the U12. [​IMG]
    It could be that the DD conversion of the U12 is better than the one inside the X-sabre.   But you will never know unless you try.
    With the right recordings and a decent system you should be able to hear some differences and then the choice is up to you.
    Good luck !
    Bye,  gino   [​IMG]
  2. ginetto61
    Hi thanks a lot for the very interesting review.  It looks like a very good designed and built unit.
    Do they have a website ?  where did you buy it from ?
    which usb and power cable are you using ?  which digital connection to the dac ?
    Thanks again,  gino
  3. bixby
    Thanks for your input.
    Regarding the USB cable, yes eliminating the power leg has resulted in a big improvement in sound.  Many XMOS based input stages do not require the USB power to be recognized and function perfectly.  To test my dac, I took a cheap USB cable and carefully opened it up (cut the outer insulation) and cut and isolated the power leg (taped).  Tried it out and it worked.
    Then a friend, who is a diy wizard started making a bespoke USB cable without the power leg.  He and several of my other friends use them and they sound great.  So I bought one of his, not cheap but not crazy either and he knows how to build it to meet USB specs regarding impedance not just slap some fancy wire onto some connectors and call it a day.  The negative line and data lines are made up with regular connectors and he uses a good geometry to keep inductance low.  When you think about it, you kill a bunch of the noise on the power leg and most of what is left is on the negative, with maybe some modulating along with the data lines.  Pretty clean though overall.  
    To me I do not see the point in translating USB to SPDIF when you already have a decent USB receiver, good dac clock and async operation.  But maybe I am missing something.  I know the big improvements I heard with my Halide and Audiophileo bridges was due the the fact I had to use USB to get the signal form the computer and the fact that many lower cost and earlier USB implementations on dac were pretty lousy sounding.  And in the case of dacs without USB, the better clock in the Audiophileo did wonders for my Blue Circle dac.
    I think I will hold off for now.  Another several hundred $ outlay may not improve things and I cannot afford to lose money on an audition.  Then again, maybe someone here will take the hit and try it with the Matrix.  
    I may have an opportunity to see how well an uber priced bridge does on a really expensive dac this weekend when I may get to hear the Hydra Z on the Rowland dac.
  4. ginetto61
    Hi and thanks a lot for the very kind reply.  And sorry but i am slow to catch up ... [​IMG]
    This is a usb cable open
    Have you left intact only the data + and - wires and cut everything else (i.e. screen, Vcc +5V and Ground) ?
    Because it is very important for me to understand this without any doubt.
    Leaving only the data wires is the only way to achieve that blessed complete galvanic isolation of the dac from the "dirty pc" i guess.
    ( it is dirty but i love it ... it is so handy ... i can do everything with it ... i love the pc for this )
    I did this as an experiment with a 2000 USD usb cable (joke [​IMG]) with a cheap cable and one of my dacs (the Cambridge Audio Dacmagic) actually worked perfectly the same
    This is how all the usb dacs with embedded power supply should work (and they should also provide a decent data only usb cable).
    I guess that in these dacs the USB screen, Vcc +5V and Ground are disconnected at the panel usb socket level
    Thanks a lot again for your very kind and helpful advice
    Kind regards,  gino
  5. bixby
    Hi Gino:
    A picture is worth a thousand words, I suppose.
    As you see the black plastic has been cut carefully all the way around along with the Braid and foil (if yours has it).  I call this the shield and for our test purposes it does not matter if it is gone.  I then cut the red wire ONLY and taped the remaining ends so it would not short against the shield.
    We want the ground (black wire usually, not to be confused with the Braid) to be intact.  When you have one made, I suppose you also get the benefit of having the braid intact all the way to screen RFI.
    The big question is how does it sound?
    Click on pic to see more closely 001.jpg
  6. ginetto61
    Hi and thanks again, but sorry in this way you will not have galvanic separation with the pc.
    I can assure you that i left only the two data wires (white and green) connected and cut everything else (screen, black and red wires)
    and the Cambridge Audio was still working perfectly.
    Clearly it has been designed very well and with some mods it could sound even better.  
    it is important to cut any electrical connection with the pc because there can be noise in the pc ground
    Then of course the ground and the +5V must be provided to the dac, if it needs them to work, from an external source (PS).
    But i see now that the screen is supposed not to be connected at the usb device ... so i think it could be kept
    Instead i bought this isolator here ... this should provide galvanic isolation i hope. Not yet received
    i think that electrical isolation from the pc is very good indeed.  All the very best dacs and interfaces provide that.
    These units can work with a usb data only cable. And they sound really good.
    The next frontier anyway is usb signal regeneration. Like a signal booster that increase i guess the S/N ratio of the usb signal and makes the life easier for the usb dac (any i read).
    But now i plan to try some isolation solution with also the cables only for data.
    Then maybe the regeneration.  But i hope to get a decent sound without it. I do not have a playback system enough resolving for very fine details.
    Thanks a lot again,  gino 
  7. stuartmc
    I made the contact through Taobao. Tanly Audio has a page there.  I set up an account on Taobao and was able to contact the manufacturer through its email relay.  I am a fan of the I2S interface and I have used it exclusively after testing the various connections between the U12 and X12 DAC and finding it to sound best in my system.  These units use the HDMI connector for I2S, so I was pleased to see that the Tanly unit was similarly equipped.   The Melodious DDC uses a different I2S connector, so I was not as interested in acquiring one. I could not make as clear comparisons with the Melodious because I would have to use the coaxial or aes/ebu connection with my DAC and to me, that would be like comparing apples to oranges.  Mind you, I was intending this little foray into DDC's for review purposes.  
    My power cables of choice are the Analysis-Plus Power Ovals.  I had six different brands accumulated in my audio closet and I once again found the Analysis-Plus cords to work best in my system.  I'm using them on the DAC and headphone amp as well.  For the USB cable, I settled on the Japanese Oyaide Neo D+ Class S.  It's very affordable, great materials and build quality, and most importantly, sounds great. 
  8. blasjw
    Sorry to interject but, I thought I should give an update on my MX-U8 issue.  Just wanted to let everyone know that I did get an RMA from Shenzhenaudio so I will be sending it back for replacement.
  9. auvgeek

    I assume they'll cover shipping both directions?
  10. blasjw

    I hope so.  [​IMG]
  11. ginetto61
    Hi and thanks a lot for the information.  I see the web site is in Chinese. I will try google translation but it will be tricky.
    I am mostly interested in AES connection because my best dacs have that kind of option. 

    But i am rievaluating the usb dac option also. I have an Hegel HD10 using this port also and i will be testing some usb isolation solutions soon, hoping to extract some more details from sound.    
    Regarding power cables i believe that can make a big difference especially with some power supplies.  I see the power cables as filter and in particular, for low consumption and digital equipment, i think that the capacitance is what matters.
    Problem is to find the electrical characteristics of various cable.  But i would like to make a test.  One high end very good cable and one cheap cable but with additional passive components in order to match the L and C of the high end cable and then listen for any difference.
    What i mean is that in the end i see the cables like a filter distributed along the cable length,  But in the end what matters are the total L and C values,
    And cable with similar values should sound quite similar.  But i am not able to perform this evaluation unfortunately. 
    Thanks again,  gino 

  12. stuartmc
    Gino, I have always been mystified by the effects of power cords. It was one of those things that I REALLY didn't want to have a significant effect on sound. I don't know about the L and C of the Analysis-Plus cords, but I'm pretty sure they have that info in their white paper. They are one of the few cable companies that are highly technical, computer modeling and testing everything they make. All of their design people have advanced degrees in engineering or physics. Thier company motto is "make me prove it."
  13. ginetto61
    Hi and thanks again for the valuable advice.  I have some feelings:
    1)   usually power cables have bigger effects on digital equipment
    2)   some equipment, i.e. those that have a better designed power supply, are less sensitive to a cable swap than other that are extremely sensitive.  For instance when i see power supplies in dacs without a mains filter at the input and a toroidal transformer i am a little puzzled.  A toroidal let everything thorugh.  All noise passes to the circuits.  To see instead a well realized power supply look at the Schiit Audio dacs, for instance.  Great power supply and not that complicated. Just well designed and realized and i think it is one reason of their very good sound.
    3)   i wonder if the same effects of a high end power cable could be obtained with a carefully matched combination of cheap shielded power cable plus a rightly selected mains filter.  For me high capacitance is key.  It tends to block the RF/HF noise that is almost always in the mains and it is so detrimental for digital circuits sound.  For instance RF is often the cause of what is called digital haze in the sound from a dac. A high capacitane power cord can do a lot to block RF noise at the cable. Of course same effect can be obtained with a filter.
    So  i am actually looking for a mains cord with high capacitance but it is difficult to find specs for a power cord.
    I could get maybe high capacitance with a very long cable i guess.
    I am planning to make a 10 meters power cord and put it on my dac.   And i wonder if i could do even without a shield.  For me the only entry possible for noise is the mains input. 
    In my city we have had a big industrial crisis.  You know that i have never heard so beautiful sound from my cd player like after they have shutdown some big factories in the aerea ?  sorry for the workers of course.
    Digital is so sensitive to power quality that is unbelievable ... analog  much less.
    Thanks a lot again.  gino
  14. abartels
    Hi Guys,
    I found this interesting site, they have the WORLDS FIRST HIGH-SPEED USB ISOLATOR
    Not cheap, but maybe a very nice add-on for us! :)
    Cheers [​IMG]
  15. Sonic Defender Contributor

    Then they need some double blind, multiple trial testing don't they? I'm sure machines can measure a difference, but how do we know we can actually hear it? I'm not a full-on objective only person, I believe in the subjective experience, but blind listening test satisfy both tests so that the subjective and objective are measured at the same time. It is telling in my mind that none of these companies that really aught to know how to set up legitimate testing procedures just keep showing us machine measurements, or they rely on sighted listening testimonials. I'm not saying these things can't make a difference, I'm just saying we need to admit that until proper unbiased testing is conducted we can't be confident in the results.
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