would it be possible to swap the converter out for one that can handle a higher amperage? What's the internal draw on the UA-5?
You'd need something that would fit in there (on the board). Might be tough. I also noticed that it comes after a DC line filter, so they took great care to make sure the power is clean before it hits the electronics. You could introduce noise by connecting another device after the filtering.
Probably not worth the effort. Easier to just split power from your source. I've got a little setup that runs the JB3 and UA-5 from a single 9.6v - straight 9.6 for the UA-5 and a regulator for the JB3 (I've used both a 5v reg and a car adapter reg set to 4.5v