Power Your Pedals Without the Guesswork

Every pedal on your board needs power.

The easiest way to understand whether your power supply can handle your pedals is to think of it as having a power budget.

Your pedals draw from that budget.

Once you understand four things — voltage, AC/DC, polarity, and current — pedalboard power becomes much easier to manage.

Think of Current as Your Budget

A power supply can provide a certain amount of electrical current, measured in milliamps, or mA.

Each pedal requires a certain amount of current to operate.

So if a power supply provides:

500mA available

and your pedal uses:

70mA

then that pedal has used 70mA of your available current budget.

You still have:

430mA remaining

available for other compatible pedals.

Your power supply provides the budget. Your pedals consume it.

Step 1: Match the Voltage

Voltage must match what the pedal requires.

Common pedal voltages include:

• 9V
• 12V
• 18V

A pedal designed for 9V should normally be connected to a 9V output.

Think of voltage as the operating requirement. It is not something the pedal gradually “uses up.” It simply needs the correct voltage to operate properly.

For example, if a pedal requires:

9V DC / 70mA

you first need a compatible 9V output.

Then you look at the available current.

Step 2: Match AC or DC

Voltage alone is not enough.

You also need to know whether the pedal requires:

DC — Direct Current

or

AC — Alternating Current

These are different types of power and are not interchangeable.

Most modern guitar pedals use 9V DC, but some pedals — especially certain older or specialized designs — require 12V DC, 12V AC, or other configurations.

Always check the pedal before connecting power.

Step 3: Match the Polarity

Most modern guitar pedals use:

Center-negative DC power

But not every pedal does.

The polarity symbol printed on the pedal or its power requirements tells you which part of the connector is positive and which is negative.

Before plugging in a pedal, verify:

Voltage ✓
AC or DC ✓
Polarity ✓

Once those match, you can evaluate the current budget.

Step 4: Check the Current Budget

This is where things become easy.

A pedal generally draws only the current it needs.

If your pedal requires:

70mA

and the power output can provide:

120mA

that's fine.

The pedal doesn't suddenly receive 120mA. It simply draws approximately the 70mA it requires.

What matters is that the supply has enough current available.

Good

Pedal requires: 70mA
Power supply provides: 120mA

✓ Plenty of available current.

Also Good

Pedal requires: 70mA
Power supply provides: 300mA

✓ Still perfectly fine.

Not Enough

Pedal requires: 250mA
Power supply provides: 120mA

✕ The output does not have enough current capacity.

Shared Current vs. Individual Current

This distinction is extremely important.

Some power supplies give each output its own current capacity.

Others provide a shared current budget across multiple outputs.

Example: FuelTank Classic

The eight 9V outputs on the T-Rex FuelTank Classic share a:

500mA 9V Current Budget

That means all of the pedals connected to those eight 9V outputs together must stay within that 500mA total.

For example:

You still have plenty of available current.

This is why the FuelTank Classic can remain an excellent power supply for a traditional analog pedalboard even though its eight 9V outputs share one power section.

Individually Isolated Outputs

Other power supplies allocate power differently.

For example, a FuelTank Junior provides separate isolated outputs.

Instead of asking:

“How much of the total 500mA budget have I used?”

you ask:

“Does this individual output have enough current for this pedal?”

If an isolated output provides:

120mA

and your pedal requires:

70mA

you’re good.

The unused capacity on that output generally does not transfer to another output unless the power supply is specifically designed to allow that.

What Does “Isolated” Mean?

Isolation is separate from current capacity.

Two outputs can provide exactly the same voltage and current while behaving very differently electrically.

An isolated output separates one pedal's power connection from another.

This can help reduce:

• Ground-loop hum
• Noise between pedals
• Interaction between certain digital and analog effects
• Problems caused by pedals with unusual grounding arrangements

A shared power supply may work beautifully with a group of conventional analog pedals.

A more complex board containing multiple digital effects may benefit more from individually isolated outputs.

The Four Questions to Ask Before Connecting Any Pedal

Every time you add a pedal, check these four things:

1. What voltage does it require?
9V? 12V? 18V?

2. Does it require AC or DC?
They are not interchangeable.

3. What polarity does it require?
Center negative? Center positive?

4. How much current does it need?
And does your power supply have enough available current?

If all four answers match, you've done most of the work.

A Real T-Rex Example

Consider the T-Rex Creamer Reverb.

Its power requirement is:

9V DC / approximately 70mA

Here’s how it fits into the FuelTank family.

FuelTank Classic

9V available: 500mA shared
Creamer uses: 70mA
Remaining 9V budget: 430mA

✓ Compatible

FuelTank Junior

Individual output: 9V / 120mA
Creamer requires: 70mA

✓ Compatible

FuelTank Chameleon

Compatible output: 9V / up to 300mA
Creamer requires: 70mA

✓ Compatible

One pedal. Three different power architectures. The same four questions tell you whether it works.

More Current Capacity Is Okay

This is one of the most common areas of confusion.

If your pedal requires:

9V DC / 70mA

it is okay to connect it to a properly matched output capable of:

100mA
120mA
300mA
or even 500mA

The important thing is that:

• the voltage is correct;
• AC/DC is correct;
• polarity is correct;
• the supply can provide at least the amount of current the pedal requires.

Think of a 300mA output as having up to 300mA available.

The pedal takes what it needs.

What Happens When You Exceed the Budget?

If the combined current requirements of your pedals exceed what the power supply can provide, you may encounter problems such as:

• Pedals failing to start
• Digital pedals rebooting
• Unusual noise
• Weak or unstable operation
• LEDs behaving incorrectly
• Intermittent performance

If your board behaves strangely after adding another pedal, check the current budget.

You may simply have exceeded the available power.

Leave Yourself Some Headroom

You don't necessarily want to build a pedalboard right on the absolute edge of the supply's rated capability.

Leaving some unused current capacity gives you:

• room to add another pedal;
• flexibility when changing effects;
• easier troubleshooting;
• a more practical long-term rig.

A little headroom is a good thing.

Build Your Board Before You Buy Your Power Supply

One of the smartest ways to choose a power supply is to make a simple list.

Write down:

Pedal
Voltage
AC/DC
Polarity
Current Draw

Then add up the current requirements where appropriate.

Now you can select a power supply based on the actual requirements of your board instead of guessing.

The T-Rex FuelTank Family

FuelTank Classic

Best suited to traditional pedalboards and mixed-voltage rigs.

• Eight 9V connections
• 500mA shared 9V current budget
• Dedicated 12V DC power
• Dedicated 12V AC power

Best for: analog and lower-current pedalboards with multiple pedals.

FuelTank Junior

Compact isolated power for straightforward 9V boards.

• Five individually isolated 9V outputs
• 120mA per output

Best for: compact boards using conventional lower-current pedals.

FuelTank Chameleon

Greater flexibility for mixed-voltage boards.

• Individually isolated outputs
• Multiple voltage configurations
• Higher current capacity
• Support for 9V, 12V, 18V and compatible AC applications

Best for: more complex boards containing pedals with different power requirements.

Know Your Budget. Power Your Board.

Pedalboard power doesn't have to be complicated.

Remember:

Match the voltage.
Match AC or DC.
Match the polarity.
Stay within your current budget.

Do that, and you're most of the way to building a quiet, reliable pedalboard.

Need help figuring out your board?

Contact T-Rex Effects USA with a list of your pedals and their power requirements, and we'll help you understand what your board needs.