N-audio Powerbox Mk2 User Manual - page 6
N-audio
Powerbox Mk2 - Regulated stompbox power supply
6
V. Center positive, center negative and negative ground effects
The majority of guitar effects are produced to be able to use a 9V battery or with an
external adapter. Of course, owing to the specificity of the schematic resolution, there are
effects which require different power supply. That is the reason why there are differences in
their power connectors. When using external power adapter, usually the jack has an external
diameter of ø5.5mm and internal - ø2.1mm. Effects which require stronger current use similar
jack, but with bigger inner diameter - ø2.5mm. That is so, because these power supply
connectors can withstand stronger current. There is also a small group of effects, which use
3.5mm mono jack. Exceptions include some processors, MIDI controllers, tube effects and
others with specific power supply, where different supply connectors are needed.
Normal polarity effects - center negative.
Guitar effects have standardized connectors and location of poles. They usually use
center negative ø5.5mm/ø2.1mm jack. The symbol, which indicates the location of the poles,
is this:
In this category we can put all guitar effects of manufacturers like Boss, Digitech,
Ibanez, Morley, Tech21, TC Electronics, MXR, EBS, Xotic, Behringer, Fulltone, Carl Martin,
Cmat mods and many others. With all of them, schematic representation looks like this:
Input
Effect
electronics
Output
DC Jack
Normal effect supply
/center negative/
Note that the negative of this effect is connected to the ground of the input and output
jacks.
Reverse polarity effects - center positive.
There are effects which operate with reverse polarity. The symbol, which indicates the
location of the poles, is this:
There are a relatively small number of effects in this category. The most notable
example of this type is Moog’s Moogerfooger line of effects. Here we include also effects
powered with a 3.5mm mono jack. Most of them are reverse polarity effects. Effects which
utilize this type of supply are Vintage Electro Harmonix, Pro Co Rat, Vintage DOD, etc. With all
of them, schematic representation looks like this: