USB Power Isolator

johnmarkp · 23rd March 2012, 11:00 PM

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.

23rd March 2012, 11:00 PM	#1
johnmarkp diyAudio Member Join Date: Apr 2004 Location: Wisconsin	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?

23rd March 2012, 11:03 PM	#2
nigelwright7557 diyAudio Member Join Date: Apr 2008 Location: Carlisle, England	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. __________________ http://www.murtonpikesystems.co.uk PCBCAD50 pcb design software.

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24th March 2012, 05:03 AM	#3
stephensank diyAudio Member Join Date: Oct 2006	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.