How much USB current can the AudioboxUSB draw. I am investigating using a USB optical isolation device to decouple the USB ground from my PC. These devices have power limits and I need to know how much power the AudioboxUSB might draw (the max including with the 48V enabled on both mic ports). I cannot find this value anywhere in the specs. All it says is USB power. I assume it is less than 500ma which is the USB 2.0 spec put many isolation devices can only provide a little over 300ma.