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Illustration: seven effects pedals wired together on a pedalboard - AI-generated artwork, not a photo of the exact product

Pedal Power Supply Noise: How to Fix Hum, Whine and Buzz

A steady hum, a high whine that changes as you turn a knob, or a buzz that only appears with pedals on is very often a power problem, not a broken pedal. Most of it comes from sharing one power source between pedals that do not get along.

Quick answer

Power the noisy pedal on its own, from a battery or a separate supply, and listen. If the noise goes away, your power setup is the cause. The usual fix is a supply with isolated outputs instead of a daisy chain, with each pedal at its correct voltage and polarity. Then route power cables away from audio cables.

See all care & repair guides

Safety and pedal care first

Match each pedal's voltage and polarity. Most compact pedals use 9V DC, center-negative, but not all. The label next to the power jack is the authority.
Check current (mA): the supply output must give at least what the pedal draws. Digital pedals often need far more than analog ones.
Never run a pedal at a higher voltage than its maker allows. It can destroy it.

Find the cause

Bypass test. Guitar straight into the amp. Is it quiet? Then the noise lives in the pedals or their power.
One at a time. Add pedals back one by one and note which one brings the noise.
Battery test. Run that pedal on a battery if it takes one. Silent on battery means the power supply or daisy chain is the problem.

Common causes and fixes

Daisy chain hum. One adapter feeding several pedals shares a ground between them, which can hum, especially with digital pedals. Fix: a supply with isolated outputs.
Digital pedal whine. Delays, reverbs and modelers can put a whine into shared power. Give them their own isolated output.
Cheap or wrong adapter. A poorly filtered adapter can add hum. Use a supply made for pedals.
Cable routing. Power cables and transformers laid next to audio cables can induce hum. Cross them at right angles and keep the supply away from the input of high-gain pedals.
Dying battery. A fading 9V can make a pedal sputter, gate or distort. Replace it.
Not power at all. If the hum drops when you touch the strings, it is coming from the guitar's grounding, not the power: see our guitar grounding hum guide. Single-coil pickups also hum near screens and lights.

When to stop

If a hum stays with the guitar plugged straight into the amp, or the amp hums with nothing plugged in, it is not your pedals. Do not open the amp. Take it to a tech.

The usual fix: isolated outputs

This is a larger investment, so do the battery test first to confirm power is the problem.

Truetone 1 SPOT Pro CS7 Isolated Pedal Power Supply

Best for Boards with digital pedals or a daisy-chain hum problem: seven isolated outputs instead of one shared adapter

7 isolated outputs: 2 x 9V, 4 x 9V/12V switchable, 1 x 18VCables and adapters included (per Truetone)

Specs: Truetone listing details, checked 2026-10-26.

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Product links checked Oct 2026 against each exact Amazon listing; Amazon shows the current price. See How we rate.

Sources checked Oct 26, 2026: Boss and Truetone power-supply guidance on voltage, polarity and isolated outputs; Truetone CS7 listing.

FAQ

Why do my guitar pedals hum?

Most often a shared daisy-chain power supply, a digital pedal on shared power, or power cables lying next to audio cables. Test each pedal on its own to find it.

What is an isolated power supply?

A supply whose outputs are electrically separate, so pedals do not share a ground or pass noise to each other. It is the standard fix for daisy-chain hum.

Can I use any 9V adapter for my pedals?

Only one that matches the pedal's voltage, polarity (most are center-negative) and current draw. The wrong adapter can add noise or damage the pedal.

Why does my delay pedal make a whining noise?

Digital pedals can push a high-pitched whine into shared power. Give the pedal its own isolated output.

How this page was made: Andrew wrote this guide from makers' manuals and support pages, listed above. Each button opens the exact Amazon listing (checked 2026-10-26), and Amazon shows the current price. How we rate