How To Handle Positive Ground Guitar Effects Pedals
All guitar effects pedals require power to function and it’s important to note that not all pedals run off of the same type of power supply.
Not only do you have to consider operating voltages, but also the necessary milliamps for that pedal to function correctly and the polarity of that power. Most guitar effects pedals require 9 volts of DC power which can be supplied by either a battery or an external power adapter.
However, if you’re going to use an external power supply for your pedals, you need to check what each pedal needs before plugging them into the power supply. Does the pedal require a negative center power supply or a positive center power supply?
What Is The Difference Between Negative Ground & Positive Ground?
The standard power adapters we use for guitar effects pedals are 2.1mm coaxial barrel connectors. This means there are two connections available within the connector. A tip and a sleeve (just like an input/output jack). The tip of the power supply is the polarity center and how this is wired will tell you what types of units it will work with.
Looking at the information on your pedal, you should be able to see the power requirements located near the power input jack. Here, you should find one of two symbols:
Center Negative or Negative Ground
Center negative power is what you will find with the majority of the pedals on your pedalboard. This is the industry standard and used by the major brands such as Boss, MXR, Ibanez etc. As you can see from the diagram, the center (tip) of this diagram shows that the pedal requires a center negative power supply.
Center Positive or Positive Ground
Center positive power is what you might find with older germanium circuits as they use PNP transistors. As you can see from the diagram, the center (tip) of this diagram shows that the pedal requires a center positive power supply. Many power adapters and effects pedal power supplies will not utilise center positive power, so we need to be clever with how we approach it.
What Types Of Pedals Require A Positive Ground Power Supply
The main types of pedals that would require a center positive power supply are fuzzes and range master type pedals. This is mainly because they utilise old germanium PNP transistors that were readily available when these circuits were first created in the 60s.
How To Correctly Power A Positive Ground Guitar Effects Pedal
Supplying the correct power to your pedals could be the difference between them working correctly and producing the exact sound you’re after, or frying the insides of the pedal and making it a very expensive boutique door stop. I’ve fried a couple of pedals in my time and it never gets any easier to stomach.
Some pedals will contain an inbuilt voltage protection circuit which may help protect your pedals from the wrong type of power. However, please do not always count on this from saving your gear. Always read the label!
Here are 4 different ways to power your positive ground effects pedals:
Option 1 – Power Cable Adaptor Method
One of the simplest ways to power your positive ground pedal is to use an adapter that takes your existing negative ground outlet and reverses the polarity.
This is a relatively inexpensive way of powering your pedal. However, if you use a daisy chain or a non-isolated power supply for your pedals, this method could create a hum in your signal chain. If you’re only looking to power one pedal off one outlet, or if you have an isolated power supply (like the MXR ISO Brick), this solution is a pretty safe bet.
Option 2 – Use A 9 Volt Battery
This may feel like the most obvious answer, but it’s often one people neglect. Using a standard 9-volt battery is how many of these vintage guitar effects pedals were supposed to be powered and have been wired up correctly to accept them.
As long as you unplug the input jacks to any pedals running off a battery, you should get a fantastic lifespan out of each battery. Whilst there is a huge amount of hearsay around which types of batteries to use to get the best ‘tone’ out of your pedal, you can’t beat a classic Duracell or Energizer battery. They’re reliable and they have a decent enough lifespan to help ensure your favourite vintage fuzz doesn’t die on you mid-set.
Option 3 – Purchase a Specific Positive Ground 9 Volt Power Supply
If you don’t mind carrying around another plug/adapter, then a stand-alone positive ground power supply is a fantastic option. By going down this route you can ensure that your pedal is getting exactly what it needs, it isn’t affecting the signal for any of your other pedals and there’s no chance of you damaging the components inside it.
Option 4 – Internal Reverse Polarity Circuit
If you’re building your own effects pedals and want to make sure that your customers don’t face any polarity issues of their own, you could integrate a reverse polarity circuit into your pedal. This essentially takes the negative ground power from your standard power supply and reverses it to work with your positive ground pedal.
It’s a super easy circuit and only requires a handful of components to achieve. You can find the tagboard layout for this here:
If you can ensure that your pedals run on standard power supplies, it’s one less thing for your customers to worry about. It’s also a way to keep them from accidentally destroying their pedals straight out of the box.
So there you have it. Four different ways to power a positive ground guitar effects pedal.
As always, if you have any questions on anything in here or would like anything added to help make this guide more useful, please get in touch and let me know.