this is from an old post of mine. warning: it in fact does not come with a regulated power supply. you will need to get one from radioshack or an electronics supply. it is very important that you have the regulated supply. it is okay to use anything from 4.5 to 5v. absolutely no more or you will fry things like your dac! 4.5v supply's actually put out about 4.7-4.8v at no load which meets usb spec. you can actually use any good hub. you will need to get the correct adapter for the psu to hub and get the polarity right or you will kill something. do not plug anything else into the hub besides your dac! for one thing the psu you are going to get does not have enough amperage.
~~position the supplied cable(the side that goes into the computer) facing up towards you so you see the pins. put a little piece of scotch tape on the pin all the way to the right. make sure the pin is completely covered with tape. now plug everything in as normal and use the usb cable of your choice. I recommend Belkin gold with this. you now have clean linear isolated +5v power that is not coming from the computer. even if your dac has self power it most likely still needs +5v from the cable to sync. do not tape the ground on the left. you can also use this trick to make a data only cable if you wish. they rarely work though. now for 20 bucks you have a comparable device others sell for $200+.. good deal. there is one caveat, with jriver at least sometimes I get an error once on start and it works the second time. do not plug anything else into the hub for best sound. it sounds real good. ......this has been edited from my original post because I had misinformation at the time. others doubted it but I can measure it as good or better than any other option. of course then there are usb filters which will further increase performance which this do not have. good clean power is a good step in the right direction. a desktop or laptop computer supplies nothing but noise on usb!
if you have any doubts about your ability do do this don't! I thought that warning was in order even though this is very simple. I am in no way liable for what anyone does. I am simply providing instructions.
you can also splice the ground on the cable and ground it to something outside the computer. any solid earth ground in a building. again, do not attempt this if you are not sure of yourself!