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Guide to Power Supplies

Voltage (V)

Most pedals nowadays require 9V DC to power them.  However, some larger or boutique pedals can demand higher voltages of 12V, 18V or 24V.

It’s extremely important that you provide your pedals with the correct voltage.  There is no flexibility here…each pedal needs to have the correct voltage supplied.  Whilst it’s technically safe to provide less voltage (although still not advisable if you want them to perform at their best) you mustn’t provide your pedal with more voltage than it’s designed for.  Too much voltage can fry and burn out your pedal’s internal electrics causing irreversible damage and rendering it useless…not good!

If you provide your pedals with less voltage than they’re designed for, you may experience sounds that the pedal isn’t normally intended to produce.  Some pedals can sound great in this instance, and it’s once believed that tone hound Eric Johnson would source half powered batteries to power some of his pedals as he felt the lower voltage provided by the battery gave the pedal a unique tone that was different had it been powered by say a fully powered battery.  It may be worth something exploring but for god’s sake please don’t use more voltage.

Pedals with different voltages

There are literally thousands of different effects pedals on the market today and whilst many of today’s pedals require 9V to power them, it’s not unusual for pedals to require different voltages, typically of around 12V or 18V.  Some pedals can even operate on a range of voltages, for instance anywhere 9V to 18V.  If you have a pedal with this characteristic, it’s worth exploring the different tonal and dynamic differences you can achieve purely by changing the voltage supplied.  It goes without saying that it’s important to be conscious that you aren’t overloading any adjacent pedals with the higher voltage if you do choose to go experiment with the voltages within the range.

Current (A or mA)

This refers to the amount of electrical current a power supply can provide and is measured in Amps (or more commonly seen as milliamps mA – there are 1000mA to every Amp).  Every pedal will require a certain amount of mA to ensure that it operates at its full capacity.  Most analogue pedals use very little electrical current (around 10-20mA, this applies to a lot of overdrive and fuzz pedals) whereas digital effects will require more.   Depending on what pedals you have and how complex they are, they may require significantly more.  Generally, you’ll find that reverbs and delays will require the greatest amount of current.  It’s always worth checking your pedals to see exactly how much each one may need to work properly.  If you look at each of your pedals, you’ll most likely see a sticker or label which tells you just how much electrical current they each require.

From our pedal board setup above you’ll see that in total the board is drawing 290mA of electrical current by adding up all the individual pedal’s current requirements.

Technically, if we were to use a single power supply that could provide 290mA to power our board, it would be able to power all of our pedals here.  BUT, it is highly recommended that you use a power supply that provides at least double the total current draw, so in this instance, a power supply that provides at least 580mA.  When a power supply is at full capacity, consequently the amount of power too, which could affect your set up.   Having a power supply with more mA to spare ensures the voltage of the supply remains at its optimum level and doesn’t drop as it struggles to give out more power.

Some single power supplies can provide a healthy amount of electrical current and can therefore power several pedals from it’s one single source.  For example, the Stagg AC Adaptor and TruTone 1 Spot PSU both provide a whopping 1700mA of output.  Given these amounts these power supplies can comfortably power a small pedal board.

How do I power more than one pedal with just one power barrel?

Most single power supply units will come with one barrel connector, however as they are capable of powering more than one pedal, you can use a daisy chain extension cable to utilise this extra power.  These are great as they let you use one power supply for several pedals, rather than having to power each pedal individually with a separate power supply.  As stated above, you will need to bear in mind the demand your pedals will be making of the power supply to ensure it’s not being overloaded. 

Daisy chain extension power cables usually come with a male 2.1mm plug at one end so you can plug the single power supply plug into this and create a multitude of additional power plugs from the one source.  Daisy chains also can have all female connectors too.  These are particularly useful if you have a pedal such as the Boss TU-3 Chromatic Tuner which has a 9V DC in and OUT socket.

Multi Power Supplies

Many popular pedals on the market require 9V of power so using a decent quality 9V power supply with the addition of a daisy chain extension is usually ample to power a handful of small pedals.  However, as a pedal setup grows and becomes more complicated power wise, these power supplies reach their limitations and can struggle to keep up with the demands of a larger number of pedals.  As a result, they can be prone to unwanted side effects such as noise and overheating which in turn could hinder the power supply’s reliability in future.

The next step up in such instances is to opt for a multi power supply or power brick as they are sometimes called.  Multi power supplies are becoming more and more sophisticated to cope with the power needs of some more complex set ups.  Whilst these power supplies are more expensive than the humble single wall adaptor, they offer greater flexibility and can ease a lot of stress and headaches by offering individual power outputs to each of your pedals.  This basically means that whilst you are using one single power supply, each of your pedals is effectively being powered by its very own smaller power supply housed conveniently within the bigger unit.

Multi Power Supplies come in many shapes and sizes.  They can differ hugely in their capabilities and versatility… what’s great for one may simply be overkill or not quite powerful enough for another.

With that in mind, it’s important to choose one that will cater for your needs.  You don’t always have to go for the most powerful unit if you’re simply looking to power a handful of 9V DC pedals, however, if your pedalboard is a little more intricate, you may need something a little more sophisticated.  Either way, there’s something out there for everybody.  If we take a look at a few examples below, we can see how the features can vary and lend themselves to different situations and set ups.

T-Rex Fueltank Junior

The Fueltank Junior is a small but powerful multi-power supply.  Each of the 5 outputs is fully isolated and can deliver upto 120mA of 9VDC power.  It also has an input voltage switch which can change between 230V and 115V.  Whilst this may not be a feature applicable to every player, it’s a great selling point for travelling musicians who would like to use it abroad where the voltage supplied differs to that of the UK.  A power supply with this basic yet powerful specification would be perfect for a small pedalboard with a handful of 9V DC pedals, however, it would certainly struggle to power some of the larger digital effects many players utilise nowadays, or some more unique pedals that use different voltages e.g. 12V.

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Voodoo Lab ISO 5

The ISO 5 can be considered a step up from the Fuel Tank Junior.  Whilst it has the same number of isolated outputs, two of these are a little more versatile and able to power pedals that run on 12V and 18V respectively.  The 12V output can also be used as a 9V output that delivers up to 400mA… ideal for one of those 'power' hungry effects.

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MXR M-238

MXR’s M238 ISO Brick boasts 10 isolated power outlets.  Six of these are dedicated to 9V DC pedals with a variety of current outputs.  Another two can deliver 18V of power.  Whilst this specification is pretty impressive alone, the key unique feature to the M-238 is its two switchable voltage outputs.  The voltage delivered by these outputs can be altered simply with the turn of a knob anywhere from 6V up to 15V in 1V increments.  This is really handy, particularly for players powering pedals that operate on a range of voltages, or for those overdrive and fuzz pedals that sound great when supplied with lower voltages.  This can also be referred to as 'voltage SAG'.

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Voodoo Lab Digital

The Voodoo Lab Digital is a unique power brick that has 4 isolated power outputs.  Whilst it may not be as versatile as the MXR ISO Brick, it’s really been designed with a specific application in mind; to provide high levels of current to a smaller number of larger digital effects units a la Strymon and Eventide.  Whilst there’s not a huge number of them, each output can provide an impressive 400mA which makes it ideal for players who may not have a huge board, but the pedals they do have require a lot of power.  400mA is a huge amount of current to deliver for one output and you could power a small pedalboard simply from just one of the power outputs!

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Truetone CS12

The Truetone CS12 is a swiss army knife of power supplies.  It’s hugely versatile and powerful and incorporates all of the features in the power supplies above.  The Truetone CS12 is also an example of a power supply that doesn't incorporate a heavy transformer making it very light in comparison to other multi power supplies.  It's also compact enough to sit underneath an angled pedal board such as the Pedal Train Classic and Novo Series so doesn't take up space on the top of a board... another important point to be conscious of.

The CS12 has two x 18V power outputs and five switchable outputs all at 100mA that can power 9V or 12V pedals as well as four more high current 9V outputs (2 x 250mA and 2 x 500mA).  This makes it ideal for powering those bigger digital pedals.  It also has a variable voltage output (much like those on the MXR M-238) that can change the voltage in 1V steps from 4V up to 9V which is great for those old overdrives and fuzz pedals.

However, the real feather in the CS12’s cap is the addition of it’s 9V AC (not DC) output that supplies a colossal 800mA.  Many of today’s pedals use 9V DC voltage, however, there are still a few pedals lurking out there that operate on AC voltage (some popular examples of this are the early versions of the Digitech Whammy Pedal).  This unique feature makes the CS12 an ideal option for players that would usually need to carry around an additional power supply for that lonesome pedal that requires AC voltage. 

The CS12 also has the switchable worldwide input voltage feature allowing you to use it overseas where the voltage input may differ.

Shop True Tone CS12 >

Isolated Power

One of the big advantages of using a multi-power supply is that each of its power outlets are ‘isolated.’    

The benefits of having such a feature are;

• Less Noise within your pedal set up

• If one power outlet goes down it doesn’t affect the rest of the chain as it would with an individual power supply

• By powering each pedal individually, you are simply drawing the current from one single outlet, rather than all your pedals drawing from one individual power source.  As mentioned above, a board of pedals that is drawing a high level of current from one source can affect the power supply’s voltage and have a knock-on effect on how your pedals perform tonally.


One other crucial factor to consider is polarity.  What the hell does that mean I hear you ask?  Well without getting too nerdy, polarity refers to the makeup of the power socket within the pedal and is of significance when it comes to which power supply you plug into it.  Your pedal will have a barrel socket and a tip within the centre of this barrel (see image below).

Polarity refers to the charge of these parts of the socket.  Typically (but not always) the inner tip of the socket will be negatively charged and is commonly referred to as negative tip or negative centre (see what they’ve done there!) and the outside barrel will be positively charged.  Visually, you won’t be able to tell the charge differences just by looking at the socket, which is why most pedals will have a small sticker next to the power socket notifying you of the polarity of the pedal.  You can tell if the centre is negative centre or positive centre by seeing which direction the centre of the black circle is pointing towards (see below). 

It’s worth knowing what polarity each of your pedals is to ensure you don’t use a supply that provides the wrong polarity.  If you do, you will inevitably risk damage to your pedals.

As previously mentioned, some pedals will have a power socket with what is known as reverse polarity or positive centre.  If you do have a pedal that has this requirement, some power supplies have dedicated reverse polarity power ports to cater for this.  You can also purchase adaptors that will convert a standard 2.1mm barrel with negative centre polarity to a 2.1mm positive centre barrel.

Power Cable Variations

Many multi power supplies will come with enough power cables to power most of your pedals.  But, as with every aspect of powering pedals it may seem, you need to be conscious of the type of power sockets on your pedals. 

The vast majority of pedals on the market require a 2.1mm negative centre power adaptor, however, as we know, some pedal manufacturers like to buck the trend and build pedals that require different connections.  For example, many of the early Electro-Harmonix pedals and the Ibanez TS-808 Tube Screamer require a mini jack connection, whereas some pedals require a slightly larger 2.5mm barrel plug such as some of the Line 6 Modelling Stompboxes.  

Some of the power cables provided with multi power supplies aren’t always compatible for every pedal on the market.  Luckily, companies like T-Rex, Diago and Voodoo Lab provide a vast range of adaptors and power cables that that can handle the needs of most pedals. 

Within these ranges you’ll find adaptors and power cables that can convert a regular 2.1mm barrel into a 2.5mm barrel, a 3.5mm TS mini jack and even alter its polarity to make it centre positive.

T-Rex, Voodoo Lab and Diago all produce cables that can convert two isolated 9V outputs into one 18V plug by combining their voltage and another to combine the current of two outputs.  Voodoo Lab also makes power cables with both straight and right-angled barrels which can be invaluable when space is at a premium on your pedal board.  It’s always frustrating when valuable real estate is being taken up by a power cable sticking out and you just can’t quite fit that last pedal in.  The additional lengths are also very handy too.  If you have a larger pedal board, the distance from one pedal to your power supply may be too great for the current length of your power cables.  Voodoo Lab offer cables that are up to 36 inches in length, so perfect for situations such as these.