Pedal Powering 101

We're musicians, not electrical engineers, and yet we are bombarded by technical jargon, notation and symbols, to which most of us either half-understand (and often get the wrong end of the stick) or just nod and agree and move along quietly.

Here we'll look at some of this terminology, and start from the ground up (no pun intended), so you know exactly what sort of juice you need to feed your stompboxes.

This is the Diago Pedal Powering 101.

What do I need to know?

For each pedal:
1) Does it require AC or DC current?
2) What voltage does it need?
3) How much current does it need?
4) What kind of plug does it use?
5) If the pedal requires DC, what polarity is the plug?

    AC or DC
  • The current type must be correct. If it requires AC, then using DC may break it and vice versa.  AC and DC are quite different, do not confuse them.
  • If it is DC, the plug polarity must be correct, or you may blow the pedal up. If it is AC then there is no polarity.
  • Some AC pedals will work from DC. Only try this on professional advice.
    Voltage
  • The voltage level needs to match within around 10% (for example, 9V is OK for a 9.6V pedal).
  • If you supply the pedal with too much voltage, the pedal may blow up.
  • If you supply the pedal with too little voltage, you won’t hurt it, it just probably won’t work.
    Current
  • The power supply must be rated at greater or equal to the amount of current required by the pedals, i.e. a 1,000mA supply is OK for a 200mA pedal. A 100mA supply is not OK for a 200mA pedal.
  • If powering a number of pedals from one power supply, the total current draw of the pedals (add them together) should be less than the available supply current. For example, if pedal A needs 50mA and pedal B needs 200mA, then the power supply should be rated at 250mA or more.
  • A pedal 'draws' the required amount of current from its power supply; a power supply can never be too big in terms of available current.
    Pedal Plug Types
  • There are 2 common types of power plugs: the barrel plug (see table below) and the 3.5mm mini jack.
  • Barrel plugs come in 2 common sizes: 2.1mm and 2.5mm. This refers to the size of the hole in the centre of the plug.
  • Both have 5.5mm outside diameter, so they are easy to confuse.
  • A 2.1mm plug will not physically fit in a 2.5mm socket.  A 2.5mm plug will fit in a 2.1mm socket, but it will be loose and not make a reliable contact.
  • 3.5mm mini jacks are the same as a headphone mini jack.

Barrel Plug Types

Complete Description:

Centre Negative/Outer Positive

Centre Positive/Outer Negative

Diago name:

Centre Negative

Centre Positive

Alternative name:

Barrel Positive

Barrel Negative

Symbol:

Alternative Symbol:

 

    Polarity
  • This only applies to DC, not AC.
  • For DC power, there is a positive and a negative contact on the plug and socket. These must be matched.
  • 3.5mm mini jacks are always wired tip positive. The ‘tip’ is the small bit at the end.
  • Barrel plugs can only be wired 2 ways, but there are many different descriptions:

Powerstation and Adaptor Specifications:

Product

Plug Type

Size

Polarity

Diago Powerstation

Barrel

2.1mm

Centre Negative

Diago Deluxe Daisy Chain

Barrel

2.1mm

Centre Negative

Diago Green Adaptor

Barrel

2.5mm

Centre Positive

Diago Blue Adaptor

Mini Jack

3.5mm

Tip Positive

Diago Red Adaptor

Barrel

2.1mm

Centre Positive

Diago White Adaptor

9V BatteryClip

-

As per a 9V battery

Diago Black Adaptor

Barrel

2.1mm

Centre Negative