Voodoo Lab Pedal Power 2 Plus - Manual (Page 11)

A device which can be powered by a single 9V battery will require
less than 70mA and can be powered by any output with the corre-
sponding switch set to NORMAL.
The only thing you can determine from the current rating of the
supplied power adapter is that the effect will draw less than the
specified value. For example, if the adapter is rated for 600mA,
you know that your effect requires less than 600mA. You don’t
know how much less.
Unregulated power adapters are rarely run at their full capacity,
which means that their actual voltage will typically be 20-30%
higher than their rated voltage. A 9VDC unregulated adapter will
usually be closer to 12VDC. If the effect doesn’t run from a battery,
it probably requires more than 100mA and should be operated from
output 5 or 6 with the switch away from NORMAL.
You can identify a switch-mode power adapter because they are very
light weight, usually specify a wide input voltage (90-250VAC),
and output DC only. They are inherently regulated so that if the
output says 9VDC, you should run the effect at that same voltage.
Some effects which specify AC will also operate from DC.
However, since AC voltages are specified as Vrms, the peak voltage
is 40% higher and a device which normally operates from 9VAC
should use 12VDC. Line 6 Modelers (DL4, MM4, etc.) are a good
example of pedals which specify 9VAC input voltage, but can be
powered from 12VDC.
Note that many devices are designed to operate from AC only, and
require the AC voltage to drive a transformer, voltage multiplier, or
derive bipolar (both + and -) power. These will not work from DC
and a Pedal Power 2 Plus can only power them using the courtesy
outlet and their supplied adapter.