[genclaymore]

I got my Gustard U12 from the thread starter, I didn't think i would notice any thing in compared to the Peachtree X1 usb to spdif converter but I did more then what i expected. I don't know how to put it in words I now just waiting for the gustard H10 just gotta wait for massdrop to do it think.

 

[pakultra]

There are commercially available data-only USB cables but they are expensive. I just cut off the red and black power wires of a Belkin Gold cable and cut off the shielding at the DAC end too. I checked with a multimeter that only the two data wires are connected between my computer and my NAD D 1050. Not the shield, not the ground, not the positive. This works beautifully with Nad and it proves that at least some DAC's usb input does not need any ground from computer to work. Interestingly, the Nad D 1050 doesn't seem to be grounded to AC power outlet either. It uses a switch type power block to provide 5V DC to the DAC. There are only two wires going from the power block to the Nad: the positive and the negative 5V DC wires.

 

[m0reilly]

small slices of electrical tape on the contacts in question at the computer side of cable also work if you do not want to do any slicing and/or dicing/spending small fortune on data-only cables. i don't see issue re leaving sleeve ground intact, or the 5v ground for that matter.

 

[Alexsander]

  There are commercially available data-only USB cables but they are expensive. I just cut off the red and black power wires of a Belkin Gold cable and cut off the shielding at the DAC end too. I checked with a multimeter that only the two data wires are connected between my computer and my NAD D 1050. Not the shield, not the ground, not the positive. This works beautifully with Nad and it proves that at least some DAC's usb input does not need any ground from computer to work. Interestingly, the Nad D 1050 doesn't seem to be grounded to AC power outlet either. It uses a switch type power block to provide 5V DC to the DAC. There are only two wires going from the power block to the Nad: the positive and the negative 5V DC wires.

Hmmm....
if it so, then is possible to make special adapter:

 

[m0reilly]

yes, an adapter will fit the bill easily. if you purchase somewhat expensive cables, the 'tape mod' is a safe alternative re cable alterations. the adapter option would be an easy choice

 

[hgpsemaj]

superceded.

 

[abartels]

  superceded.

 
I will try to make cable today and test, but, PCB U12 needs ground, so using GND IEC320 and connect to USB Chassis connector

 

[rurika]

 http://www.head-fi.org/content/type/61/id/1356208/width/500/height/1000/flags/LL

Well, I actually use that Teradak 9v and 5v LPSU. It came with adapter like in the picture but I didn't use it (cause I have Acoustic Revive usb cable with separate data cable and +5v cable).
Didn't even test the U12 with regular usb cable cause I'm too lazy to do that .... (the +5v end always connect to Teradak LPSU)
 
Even W4S dac with usb input that use Galvanic isolation still improve when feed it with +5v from LPSU.

 

[Alexsander]

  Well, I actually use that Teradak 9v and 5v LPSU. It came with adapter like in the picture but I didn't use it (cause I have Acoustic Revive usb cable with separate data cable and +5v cable).
Didn't even test the U12 with regular usb cable cause I'm too lazy to do that .... (the +5v end always connect to Teradak LPSU)
 
Even W4S dac with usb input that use Galvanic isolation still improve when feed it with +5v from LPSU.

if you used a cable from a kit: (in it shield is connected!)........ or not (I am not sure).....?

 

[rurika]

I'm not sure what the shield that you are talking about but it looks exactly the same as your picture.

 

[Alexsander]

  I'm not sure what the shield that you are talking about but it looks exactly the same as your picture.

you can check a tester ?
I will do DIY adapter as on the scheme (Scheme Special USB-Audio Adapter)

 

[abartels]

Why not buy cheap USB card from Apexi? The new Elfidelity AXF-100 II ( Pro ) version is an updated version with galvanic isolation for power.
You can feed it with external supply, regulated, non-regulated and Battery power!
 
I ordered mine at Head-Fi member hpgsemaj, he's very helpfull 

 
Btw, this card only cost about $50 , it's a real bargain 

 



 
 
The translation is from "Mr. Google", so it's a litle gibberish, but it explains a lot.
 
Elfidelity AXF100 Pro - USB isolator audio filter for PC

Perfect product for anyone using a PC or HTPC as a source with a converter (DAC)

 

USB.

Componentbased and highend connectivity, it will clean the USB port of the noise

by the switching power supply while allowing injection if you wish 5V "clean" from an

external source (battery, power supply Linear etc. ..).
 
This product integrates an advanced power management can automatically switch if for

example the external power supply were to no longer power the module correctly.

 

Specifications:

Maximum current: 5A

Maximum Power: 25W

Automatic power switching speed: <5ms

Ripple factor: <1Hz

Japanese capacitors

Shielded Inductors TDK

Takamisawa Relais Japanese

Dimensions (PCB): 90 x 60 mm

Weight: 130 g

 

Green light (DATA)prompt in the builtin power supply state

Red Light (External Power)prompt in external power supply state

Yellow light (Build in Power)prompt whether USB signal access

 

For the protection of USB signals:

• Native nonbridging

USB signal access, starting from the bus and drive to find the most simple level design, to avoid jitter.

 

• Hardware layer in strict accordance with the design specifications differential traces,

through industrial level of EMI test

 

• Builtin power supply directly introduced from the power source, completely isolated USB bus power, avoiding the motherboard, other electrical equipment interference

 

• Multiband, progressive times, the ultimate power filter design provides high stability, highpurity current

 

• Power dynamic compensation technology, large dynamic automatic compensation, providing constant ripple

 

• Less than 1Hz pure power! Multimode power input seamless switching, intelligent protection design

 

 

For USBpowered

security:

• internal and external selfpowered identification, automatic switching, selfprotection.

external power supply is lower than 4.8 V or removed, automatically and seamlessly switch back to the builtin

power supply. Device is not lost, not be damaged.

 

• Shutdown automatically disconnect the external power supply to ensure USB audio device completely powered off, prevent no signal load to damage to the equipment, energysaving external power supply.

Intelligent power optimization design.

 

Choose a variety of external power supply, especially designed for optimizing the use of battery

power

 

• Automatic monitoring, when battery loss of pressure and removed automatically switch builtin power supply, without having to manually select

 

• Automatic shut off external power supply, protective equipment, to save battery

 

• Filter mobile power supply ripple boost circuit
 
 
 
 
So, no hastle with self-made adapters, this is just perfect!

 

[hgpsemaj]

  Why not buy cheap USB card from Apexi? The new Elfidelity AXF-100 II ( Pro ) version is an updated version with galvanic isolation for power.
You can feed it with external supply, regulated, non-regulated and Battery power!
 
I ordered mine at Head-Fi member hpgsemaj, he's very helpfull 

 
Btw, this card only cost about $50 , it's a real bargain 

  
 
Please be informed that I do not do including postage postal service any more.
 
Hence, the price for each of the 'Elfidelity USB II card AXF-100 Pro' is RMB148.00 excluding transportation cost and postage.

 

[pakultra]

I have tried Elfidelity usb card (AXF-100 pro) and it does sound better than without it. This makes me believe that U12 will sound even better if we can mod it so that it does not need usb power anymore. Even the "Cleanest" usb power will not sound as good as No usb power. 
 
Has anyone tried bypassing the U12's USB power relay switch exactly the way it is shown below?
 

 
The upper part of the picture is the original schematic of the JQC-3F relay that U12 uses. The lower part is how it can be bypassed simply by using a hookup wire to connect two spots like the way the red line is drawn. This should put U12 into a permanently powered on mode, so that it does not need usb power to turn on. 
 
I am thinking about bypassing the relay this way and using my data-only cable with U12 so that there will be Zero pollution from USB power. 
 
Has anyone tried this already? Does it work?

 

[abartels]

  I have tried Elfidelity usb card (AXF-100 pro) and it does sound better than without it. This makes me believe that U12 will sound even better if we can mod it so that it does not need usb power anymore. Even the "Cleanest" usb power will not sound as good as No usb power. 
 
Has anyone tried bypassing the U12's USB power relay switch exactly the way it is shown below?
 

 
The upper part of the picture is the original schematic of the JQC-3F relay that U12 uses. The lower part is how it can be bypassed simply by using a hookup wire to connect two spots like the way the red line is drawn. This should put U12 into a permanently powered on mode, so that it does not need usb power to turn on. 
 
I am thinking about bypassing the relay this way and using my data-only cable with U12 so that there will be Zero pollution from USB power. 
 
Has anyone tried this already? Does it work?

 
pakultra,
 
Good to hear AXF-100 Pro increases SQ on U12.
 
Bypassing relay is not the solution. Problem is GROUND NOISE. And, ground noise interferes with Data +/-
 
AXF-100 Pro is galvanic seperated and should prohibit ground noise from pc interfering Data +/- to U12.
 
Best is to use AXF-100 Pro with battery power. No noise at all.
 
 
I wanted to test last weekend but didn't had time for it. Will check it as soon as possible.