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!