speaker simulating direct box schematics (phantom powered)

[jbm222]

I want to build a speaker simulator so I can run a guitar direct into a PA (and possibly for recording), and since you need a direct box after it anyway, I figure why not build one in a direct box.  I know there are companies out there that make them, but I can't seem to find a schematic.  What I really want is to be able to do is build it out of a passive DI (which i already have), and run it on phantom power (from a mixer).  I don't know much about how phantom power works, so I don't know if this can be done.  But if anyone knows how to do it, please let me know.  

If its not possible to do the phantom power thing, i'll just build a 9v one and gut the DI and put it all in a bigger box to make space for a battery.  There's plenty of schematics out there for these.