N-audio Powerbox Mk2 User Manual - page 7
N-audio
Powerbox Mk2 - Regulated stompbox power supply
7
Input
Effect
electronics
Output
Reverse polarity effect supply
/center positive/
DC Jack
The difference with normal polarity effects - center negative is only that the polarity is
reversed. The negative of the power supply is connected to the ground, connecting the input
and output of the effect. These effects can be used with Powerbox Mk2, with the addition of a
reverse polarity cord to the normal supply cable. When you power such effect with Powerbox
Mk2, the second output can be used to power either a normal center negative or center
positive effect.
Positive ground effects.
A bit of history: After the radio lamps, the era of the first guitar effects begins with
Germanium transistors. They used these because in the 1960s and 1970s silicon (BJT)
transistors (which are widely spread nowadays) were not very popular. Transistors are two
types: PNP and NPN. Due to the technological features in the development of germanium
transistors, PNP transistors were cheaper to produce and more widespread. This is why many
effects utilized exactly such transistors. PNP transistors are characterized bythe fact that the
positive pole is connected to ground.
In the group of positive ground effects we can find Dallas Rangemaster, Fuzz Face, Tone
Bender, some versions of Octavia and others; in general – effects built with PNP transistors. For
safety reasons, in most of them a supply connector for an external adapter is omitted, but
nevertheless there are some with supply jacks or modified ones with added supply output.
Schematic representation for them looks like this:
Input
Effect
electronics
Output
Positive ground effect supply
/center positive/
DC Jack
Note that the ground is connecter to the positive pole of the power supply. Such effects
can be powered by Powerbox Mk2. In almost all cases, the power supply hasreverse polarity,
and a normal cable with a reverse polarity cord have to be used. It is important to know that
when you are powering such effect, the other free power output in the group should not
be used with a normal or reverse polarity effect. In it you can power only a center positive
effect.