Just to make it clear for everyone. You can power the H9 or any other Eventide pedal by using one single 300mA outlet set to 12V ad using the green Flex cable.
You can power any two Eventide pedals with the two 300mA outlets of DC5, remember the 12V setting and the green Flex cable.
And BTW, you can’t use the #8800 parallel adapter Flex with two outlets with different current ratings. The two outlets used MUST have the same voltage (voltage setting) and the same current rating. So for ex. using two 300mA on the DC5 both set to 12V with #8800 parallel adapter Flex will power say a Kingsley tube pedal which needs 12V and 500mA…. or the Line6 M9, yes the M9, just remember the 12V setting on both 300mA outlets, use the #8800 parallel adapter Flex followed by the green Flex. The M9 draws just below 500mA at 12V DC.