Hi, we only officially test and support power supplies made by Cioks such as the DC7 or the Eventide PowerMax and PowerMini. On those devices, a 12V 500mA outlet works for the H90.
The same configuration may work on the Canvas 15, but our official recommendation is 12V 600mA for power supplies other than the ones listed above.
I would suggest contacting the manufacturer (Walrus) and asking them how they recommend you power a devices that requires 12V 600mA with a center negative connecter. Or perhaps another user on this forum has experience with this power supply.
You may end up needing a current doubling cable or a polarity reversing adapter.
