Voodoo Lab Pedal Power 2 Plus - Manual (Page 10)

Positive Ground Effects
Almost all DC powered effects are negative ground. This means that
the negative terminal of the battery or power supply is connected
to audio ground. There are a few exceptions which are positive
ground, such as some vintage germanium transistor designs and
octavia-based circuits.
When you combine negative ground and positive ground effects
in the same system, you must isolate power between them.
Attempting to power both types of effects with a common ground
(non-isolated) power supply or a daisy-chain cable will short the
output of the power supply causing your effects to shut down and
possibly damaging the power supply. Since Pedal Power’s outputs
are isolated, it will work fine.
Reversed Polarity
Almost all guitar pedal effects use a center negative barrel jack
for power. This is considered standard polarity. Barrel jacks
wired for center positive are considered reversed polarity. You
can power reversed polarity effects with a Pedal Power by using
the correct reversed polarity cable. It doesn’t matter that the
effect is negative ground or positive ground, both types can be
wired for either polarity.
The black barrel cables included with your Pedal Power 2 Plus
are standard polarity center negative. The 3.5mm mini plug is tip
positive, which is also standard for pedals which use this connector.
About Power Requirements
Most manufacturers don’t specify the actual power usage of their
effects. The labeling on the effect and their specifications more
often will match the ratings of the supplied adapter only. Here are
some tips to help you determine if the effect can be powered by
your Pedal Power 2 Plus.