A new version of the hiface has been released which incorporates in the box a battery charger & a 5V supply. This means no need for sourcing a battery charger. Here's what a reviewer had to say about the MK2 version
"there is a definite improvement with the Mk2. So what changed? Well, the space and resolution around individual instruments and singers was improved, which led to a much better appreciation of the soundstage. Better depth, width and height were readily apparent. I could detect no downsides to this: there was no trace of any kind of glare or harshness, listening fatigue never set it. In fact this unit was responsible for more than a few late nights chez Morrin. A curious thing: I found myself not needing to turn up the volume to hear small details in the recordings. These improvements, coupled with the neat box it’s now housed in, and the built in charger, all make this a significant step up from the Mk1."
With the MK2 there is no power coming from the USB connection so the PS of the PC is of little concern. The single battery is powering the clocks & will last for days before needing a recharge - it is topped up when the unit is switched off. The new internal 3.3V regulator is ultra low noise & it supplies the Xilinx output stages!
Some consideration should be given to the external 9V to 12V power supply. Remember, this is the feed for the 5V & 3.3V regulators in the MK2 modified Hiface box so the cleanest possible power is advisable. Yes the switched mode power supplies that come with most modern appliances WILL PROBABLY DO - you know the light ones. But it is better to use a better quality PS i.e. probably one with a transformer in it (i.e heavier).