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johnmarkp 23rd March 2012 11:00 PM

USB Power Isolator
I was wondering if anyone has done a DIY version of the Aqvox USB power supply for USB audio. They use an external PS to run the downstream USB device, like a DAC. I am using the exaU2I USB to I2S converter. Most of the power comes from the USB buss. I think it may benefit from a device like the Aqvox. I do not believe that Aqvox provides any isolation on the signal lines. I think they cut the 5v power line and power ground and put a 44 ohm resistor in line. This keeps the host happy. The then use their 5v supply for the downstream device. I am wondering if it is really this simple?

nigelwright7557 23rd March 2012 11:03 PM

With my USB mixer I cut the 5 volts completely leaving the data and ground intact.
So all the power used comes from a mains adaptor.

stephensank 24th March 2012 05:03 AM

The problem with both setups you two mention is that there is no ground isolation. The computer's ground is just as large a source of noise pollution as the supply line. Ideally, in a hard-wired setup, power & power ground should be idependent, and the data line should be transformer-coupled, so there is no direct connection to the pc at all.

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