The Complete Guide to Powering Your Guitar Pedals

Wall warts, daisy chains, isolated bricks, milliamps, polarity dots… pedal power trips up a lot of players. This guide breaks down everything you need to know to power any pedalboard safely and quietly — plus a searchable database of power specs for 1,299 pedals across 23 brands.

The three numbers that matter

Before you plug anything in, every pedal answers three questions. Get all three right and you are good to go; get one wrong and your pedal either won’t turn on — or, in the worst case, gets damaged.

Voltage: match it exactly

Voltage is electrical pressure. Unlike current, voltage is not something the pedal “takes only what it needs” from — you must supply the exact voltage the pedal is designed for. The overwhelming majority of guitar pedals run on 9 volts DC. Some run on 12V or 18V, and a handful of vintage or boutique designs use 24V or higher.

Feeding a 9V pedal 18V can destroy it. Feeding an 18V pedal only 9V usually just means it won’t work right (less headroom, or it won’t turn on) but generally won’t damage it. Either way: match the voltage on the pedal’s label.

Amperage: give yourself headroom

Current draw is measured in milliamps (mA) — 1000 mA = 1 amp (A). Think of it as how thirsty the pedal is. The golden rule: a pedal only draws the current it needs. If a pedal needs 50mA, you can safely plug it into a 500mA output — it will simply take its 50mA and ignore the rest. There is no such thing as “too much” available current.

The danger is the opposite: not enough. If an output supplies less current than a pedal demands, the pedal may not power up, may glitch, or may make noise. As a rule of thumb:

Polarity: the little dot diagram

A DC barrel plug has two contacts: the tip (the center pin) and the sleeve (the outer barrel). Polarity describes which one is negative. The guitar-pedal standard — set decades ago by Boss — is center-negative: the tip is negative, the sleeve is positive. Nearly every pedal and nearly every pedal power supply follows this convention.

You’ll see a little symbol near the jack: three circles, with the center dot wired to either the minus or the plus sign. If the center dot connects to the minus sign, the pedal is center-negative. A few pedals — some vintage designs and certain boutique builds — are center-positive instead.

AC vs DC power

Almost all pedals run on DC (direct current). A small number of pedals — some Electro-Harmonix models, certain digital units, and a few others — require AC (alternating current) from a special transformer, and AC power has no polarity. This matters because:

One more trap: “ACA” on older Boss pedals does not mean AC. It’s a DC adapter standard — those pedals still take DC, just calibrated around a 12V regulated supply. (See the notes column in the database below.)

Jack and connector sizes

The near-universal standard is a 2.1mm inner-diameter barrel plug. A few things to watch for:

Quick test: loosely fit a standard disconnected 2.1mm cable into the pedal’s jack. If it seats snugly you need 2.1mm; if it’s loose you probably need 2.5mm.

Daisy chain vs. isolated outputs

This is the single biggest decision when buying a power supply, so it’s worth understanding.

Daisy chaining (non-isolated)

A daisy chain is one power source split to several pedals along a single cable — like a power strip. It’s cheap and simple, and for a board of low-current analog pedals it often works fine. The downside: all those pedals now share one common ground, which can create ground loops — the dreaded 60-cycle hum — and lets digital pedals inject noise into your analog ones. A single high-current adapter like the Truetone 1 Spot, split with a daisy-chain cable, is the classic example.

Isolated outputs

An isolated supply gives each output its own electrically separate power section. No shared ground means no ground-loop hum and no cross-talk between pedals — a noisy digital reverb can sit next to a high-gain fuzz with no interference. Isolated supplies cost more, but they’re the standard for any serious board, and essential once you mix digital and analog pedals.

How to size a power supply

Three steps:

Special cases & power tricks

Pedals that need 18V, 24V, or more

If a pedal needs more voltage than your supply offers, a voltage doubler cable combines two outputs of the same voltage (e.g. two 9V outputs → 18V). Note that some doublers limit the available current, so check that the pedal’s draw still fits.

Pedals that need more current than one output gives

A current doubler (not the same as a voltage doubler!) combines two same-voltage outputs to add their current together — e.g. two 9V/500mA outputs → 9V/1000mA — for very hungry digital pedals.

Voltage sag

Some players intentionally under-power certain fuzz and overdrive pedals to get a spongy, gated “dying battery” tone. A few supplies offer a variable “sag” output for exactly this. Only do it with pedals known to tolerate it.

Batteries

Most 9V pedals still accept a 9V battery, which is inherently isolated and hum-free — fine for a single pedal, but impractical and expensive for a board. Note that plugging a cable into many pedals’ input jack is what switches the battery on, so unplug your guitar when not playing to save the battery.

Power supplies we carry

Here are the pedal power supplies currently in stock at City Music Annex, grouped roughly from simple daisy-chain adapters up to fully-isolated pro bricks. Click any one for full details and current pricing.

Stock changes often — if something here is sold out, browse our full catalog or get in touch and we’ll help you find the right supply for your board.

Pedal power database — 1,299 pedals, searchable

Search by pedal name or brand, or filter by brand and voltage. Click any column header to sort. Unless a row says otherwise, voltage and polarity are 9V DC, center-negative. Current draw figures are manufacturer specs and independent measurements compiled by the community — use them as a close guide, and always defer to your specific pedal’s label.