Anyone know the polarity of the DC jack on the beaglebone black?
awesome… glad we cleared that one up. 
All DC barrel connectors have the same polarity, so that people don’t shock themselves by accident. The outside conductor of the barrel connector is gnd.
Is this a new thing? I remember having to check, and the multi-voltage adapter having the ability to switch polarity for that purpose…
Back in the 1970’s and earlier, positive ground electronics and PNP transistors were common…and the positive barrel jack… Most of those have burned up by now lol!
Well guess that makes life easier for me… Learn something new everyday as they say! 
Thanks for cluing me in guys!
The board uses the same power supply as the Beaglebone. 5VDC, 1A, 2.1mm, center positive. The power supply is not supplied with the board.
Sources for supplies that work include:
Adafruit
Sparkfun
http://circuitco.com/support/index.php?title=BeagleBone_Black_Accessories
I have several devices with “wrong” polarity.
That is because you are at heart, bi-polar!
Yes DC is the center pin on the connector.