The Prime PSU has a USB pass through which applies improved power to the USB bus for use by the Director.
I think the data sheets are in the public domain now. So this should be clear, if you read the data sheet. If you don't, then it won't be.

I just checked Duncan's Meridian Info, they have the Data Sheet with photos and pricing.
For my computer system, $1250 US is just a little steep.
I'm looking into getting a iFi Gemini USB cable and their external iUSB power supply, it's about $400 US for the pair which I think is reasonable.
I'm having a tough time swallowing a $1250 power supply for a $700 DAC. I would have much rather liked it if Meridian repackaged a better power supply with the original Director DAC and charged more like $1200. That would have been a little more reasonable.