Someone PMd me about this on head-fi regarding my V-DAC. Here is the response I gave him:
Actually, I had an old USB-12V DC power cable that I used instead of cutting the one that came with the wall wart--I figured it would be better to have in case something happened to the PS.
What I did was cut off that cable at about the 3-inch mark by the 12v plug. I then stripped the wire down to the 3 leads (black, red, white) and the foil shield. I had an old 12awg extension cable that I cut off about a foot from. This had 3 leads also: green, red and white.
On the 12v cable, I twisted red and white together and left the foil intact and unfurled for use when I taped. I then twisted red and white on the cut extension cable. I connected (twisted, then soldered) the black to green, red-white to red-white (both from 12v cable to extension cable). I wrapped the black/green tightly with electrical tape, then wrapped the foil ground around the whole assembly (touching the red/white wiring) and wrapped that tightly in electrical tape around the entire cable. I added heat-shrink tubing to make it look a little better.
Finally, I stripped off the wire ends on the other side of the extension cords. I twisted the red-white together and left the green by itself. I then soldered these onto red and black banana plugs (yes, the same as used for speakers); with the red-white combo going to the red and the green (in my case) going to the black. These then plug into the same colored binding posts on the power supply.
I don't have a site for pictures so I can't include any, but this is basically the process. Others on head-fi have also mentioned this process in the V-DAC thread, though it is a long read (about 1000 posts?).