[Alexsander]

  I'd like to report that I just tried bypassing the relay like it is shown in red below
 

 
The U12 turned on fine but my computer does not recognize it with a data-only usb cable. The same cable works well with my Nad D1050 usb input. So the problem lies not with my PC or my cable. 
 
Of course, as soon as I switch to a regular usb cable, my pc starts to see U12 and everything starts to work.
 
It seems that even though U12 is turned on, it still needs to sense the presence of usb power before it starts to send out data to communicate with my computer. Anyway to get around this? Is there a way to trigger U12 to start communicating with PC without the 5V power connection?

Try to return USB Ground in cable. 
It has to work (into cable must be: D+, D-, GND)

 

[stuartmc]

Now this one surprised the heck out of me....I dusted off my Audio Alchemy DTI Pro 32 with the power station 4 and inserted it between the U12 and X12. I set it on 24 bit dither and it sounds amazing when using Tidal from my tablet. Deeper bass, better imaging and the midrange is more lush. I can switch directly between this feed and a direct I2S connection and the improvement with the DTI is unmistakable. Holy cow, I'm going to pull out more of this old school stuff from my Audio closet!

 

[pakultra]

I've found a work around!
 
D+, D- and Ground didn't work - the computer still doesn't see my U12.
 
It turns out that U12 needs usb power for handshake ONLY. 
 
I made a cable like this:
 

 
One cable for data, and one for power. Plug in the data, then plug in the power, the computer will see U12 immediately, then just unplug the power. U12 will keep working beautifully with my computer without any usb power. Now, finally, I can completely get rid of usb power pollution.
 
The only problem is, after rebooting my computer, U12 will be lost. I will have to plug in power for a second to make it seen and then unplug the power again.
 
The good news is that U12 sounds its best now. The bad news? My newly bought Elfidelity usb card seems useless for now...

 

[genclaymore]

What about some kind of power adapter with a switch on it to turn off the power and back again at a press of a button. So you don't gotta reach around and pull it out to do it. That way you plug the power side into it. If you get what i mean.

 

[pakultra]

  What about some kind of power adapter with a switch on it to turn off the power and back again at a press of a button. So you don't gotta reach around and pull it out to do it. That way you plug the power side into it. If you get what i mean.

 
Good idea!
 
I will try to find a nice DPST switch to do this more elegantly. Meanwhile, I hope we will still be able to find a way to get rid of the usb power handshake requirement. My NAD D 1050 doesn't need power handshake, why must U12 need it?.

 

[hgpsemaj]

   
Good idea!
 
I will try to find a nice DPST switch to do this more elegantly. Meanwhile, I hope we will still be able to find a way to get rid of the usb power handshake requirement. My NAD D 1050 doesn't need power handshake, why must U12 need it?.

 
For XMOS derivative version of the standard design, it connects the GROUND with the computer via the USB cable.
 
For high-end model, they got their own designed galvanic separate power supply. Mr. Huang of Gustard claimed the truly galvanic separate in our market at this moment is 'Hydra Z' of Audiobyte.
 
Does 'NAD D 1050' run by Xmos?
 
 
 
Regards,

 

[pakultra]

 

   
Good idea!
 
I will try to find a nice DPST switch to do this more elegantly. Meanwhile, I hope we will still be able to find a way to get rid of the usb power handshake requirement. My NAD D 1050 doesn't need power handshake, why must U12 need it?.

 
For XMOS derivative version of the standard design, it connects the GROUND with the computer via the USB cable.
 
For high-end model, they got their own designed galvanic separate power supply. Mr. Huang of Gustard claimed the truly galvanic separate in our market at this moment is 'Hydra Z' of Audiobyte.
 
Does 'NAD D 1050' run by Xmos?
 
 
 
Regards,

 
Yes NAD D 1050 uses Xmos and I've using the same V2.23 driver with Nad before I added U12 to the link. That's why I am sure Xmos can run without ground or Vcc. 
 
I just found an interesting article from XMOS publications:
 
https://www.xmos.com/download/public/XMOS-USB-Device-%28XUD%29-Library-%28documentation%29%282.2.1rc0.a%29.pdf
 
On page 12 it says this:
 
4.1.2 PwrConfig
The PwrConfig parameter to XUD_Manager() indicates if the device is bus or self-powered.
Valid values for this parameter are XUD_PWR_SELF and XUD_PWR_BUS.
When XUD_PWR_SELF is used, XUD_Manager() monitors the VBUS input for a valid voltage and
reponds appropriately. The USB Specification states that the devices pull-ups must be disabled
when a valid VBUS is not present. This is important when submitting a device for compliance
testing since this is explicitly tested.
If the device is bus-powered XUD_PWR_SELF can be used since is assumed that the device is not
powered up when VBUS is not present and therefore no voltage monitoring is required. In this
configuration the VBUS input to the device/PHY need not be present.
XUD_PWR_BUS can be used in order to run on a self-powered board without provision for VBUS
wiring to the PHY/device, but this is not advised.
 
This explains why U12 disables its data communication until a valid USB power is sensed. It does this to pass USB compliance test.
 
This also tell us that there are very simple ways to disable the VBus monitoring function: we will need Gustard to issue a special firmware that changes its PwrConfig from XUD_PWR_SELF to XUD_PWR_BUS, this will tell the machine not to check for USB power presence.
 
Or, we will need someone who knows how to mod an existing firmware to change its PwrConfig status to bypass Vcc check. 
 
Nad has issued several firmware updates for its D1050 since its launch. Perhaps it is time that Gustard issued a special firmware update for us who'd like to run U12 without Vcc?

 

[abartels]

That switchbox sounds like a winner. Do you plan to sell some? Or is there any commercially available one?

I don't plan to sell one, and i don't know if they are commercially available, but i will explain how to make one yourself later on.

 

[AKAI]

Question for my U12
 
I received my Gustard U12 yesterday, I was able to use it through my Vortexbox with both my W4S DAC2 (AES/EBU), and my Marantz SA8005 (Coax). It was working fine, I turned off the Vortexbox and the U12 turned off itself (I think it went into the stand by mode), I could hear a click from the U12.
 
After dinner, I tried to fire up the U12 again, it showed correct resolution from my Vortexbox both 44.1 and 88.2, both of my DACs showed correct resolution corresponding to the Vortexbox and the U12, however, THERE WAS NO SOUD!!
 
It appears as if both of my DACs received the signal from the U12 but Unable to Decode?  I am not sure what happened as am seeking explanations from those that are familiar with the unit., There is no ON/OFF switch on the U12 or a reset switch and I am at a loss on what happened.
 
My set up is Vortexbox USB -> Gustard U12 AES/EBU -> W4S DAC2
                                                  Gustard U12 Coax -> Marantz SA 8005
 
Both were working fine but now NO SOUND as if both DACs are unable to decode the signal from the U12.
 
Thanks,
 
Akai

 

[hgpsemaj]

  I've found a work around!
 
D+, D- and Ground didn't work - the computer still doesn't see my U12.
 
It turns out that U12 needs usb power for handshake ONLY. 
 
I made a cable like this:
 

 
One cable for data, and one for power. Plug in the data, then plug in the power, the computer will see U12 immediately, then just unplug the power. U12 will keep working beautifully with my computer without any usb power. Now, finally, I can completely get rid of usb power pollution.
 
The only problem is, after rebooting my computer, U12 will be lost. I will have to plug in power for a second to make it seen and then unplug the power again.
 
The good news is that U12 sounds its best now. The bad news? My newly bought Elfidelity usb card seems useless for now...

 
This could be a solution, save up the time a bit and more economical. It offers 0.75m, 1.5m, 1m, 2m or 3m for the same price RMB131.10 excluding postage.

 

[prot]

Question for my U12

I received my Gustard U12 yesterday, I was able to use it through my Vortexbox with both my W4S DAC2 (AES/EBU), and my Marantz SA8005 (Coax). It was working fine, I turned off the Vortexbox and the U12 turned off itself (I think it went into the stand by mode), I could hear a click from the U12.

After dinner, I tried to fire up the U12 again, it showed correct resolution from my Vortexbox both 44.1 and 88.2, both of my DACs showed correct resolution corresponding to the Vortexbox and the U12, however, THERE WAS NO SOUD!!

It appears as if both of my DACs received the signal from the U12 but Unable to Decode?  I am not sure what happened as am seeking explanations from those that are familiar with the unit., There is no ON/OFF switch on the U12 or a reset switch and I am at a loss on what happened.

My set up is Vortexbox USB -> Gustard U12 AES/EBU -> W4S DAC2
                                                  Gustard U12 Coax -> Marantz SA 8005

Both were working fine but now NO SOUND as if both DACs are unable to decode the signal from the U12.

Thanks,

Akai

Did you try restarting everything again? And/or connect only one Gustard output. Also make sure that everything is fine without the gustard in the chain.

If all that fails you may have a defective unit and you'll have to contact support.

 

[AKAI]

Thanks Prot, tried unplugged, restarted, unplugged USB from both Vortexbox and U12, nothing.  Reduced the output to just Coax, no sound.
 
Frustrated and puzzled, it was working fine when I first received it. Still looks like the U12 sends the signal to the DACs but the DACs can't decode it.
 
What is wrong with it?

 

[prot]

Thanks Prot, tried unplugged, restarted, unplugged USB from both Vortexbox and U12, nothing.  Reduced the output to just Coax, no sound.

Frustrated and puzzled, it was working fine when I first received it. Still looks like the U12 sends the signal to the DACs but the DACs can't decode it.

What is wrong with it?

Did you install any special drivers on that vortexbox? Could be that it recognized/configured the gustard wrong after the restart. Slim chances but just try another source.
If everything works fine without the gustard in the chain and another source fails too I'm out of ideas.

 

[AKAI]

Thanks Prot, tried almost everything, no driver on my VB.
I just tried my Augio-GD DI-2014 with VB the same way as the U12 and the Audio-GD works flawlessly.
I also tried USB from my VB directly into my Marantz DAC again, and it works.
I guess it is the U12 that is defective.
 
Just trying to find out if anybody knows which part of the U12 causes it to output signal that perhaps corrupted.

 

[pakultra]

I'd like to share with you my some of my test results.
 
I connected U12's optical out to my Sound Blaster ZXR input and used RAMM6 to measure how U12 scores with different power supply and connection alternatives.
 
Test link: pc => Elfidelity card => U12 input => U12 optical out => ZXR optical in 
 
Here are the results:
 

 

 
 
In terms of performance, Elfidelity +5V > D+, D- , motherboard ground > D+, D- only > motherboard +5V.
 
The biggest differences can be seen in noise level, THD and stereo crosstalk.
 
Please note that these tests are done with Belkin Gold usb cable. Belkin Gold's power wires and data wires are not shielded from each other, so they are more susceptible to power pollutions.  
 
Next I will test a 3 wire connection (D+, D- and Elfidelity ground only).