POWER SUPPLY NOISE   Encountered by guitarists using power supplies to power their effects pedals
SOUNDS LIKE   lots of different things (sorry)  🙁

2015 LogoBlueRGB-68-168-203 WEBw500onBLKGuitar Noise Manual    by PedalSnake®


Jody Strat 2 Crop 200Jody Page, PedalSnake’s inventor and lifelong pro guitarist, is an electrical engineer (a member of NASA’s Space Foundation Hall of Fame, no less) with special training in electrical noise.  In the Guitar Noise Manual, Jody starts by breaking down guitar rig noise into 6 types:


For each noise, Jody explains its causes, then offers a targeted set of solutions.  Also included are several helpful articles on general best-practices for noise reduction.




Before We Start…

So What’s the Deal With POWER SUPPLY NOISE?

What can cause power supplies to be noisy?

A noisy power supply model

A damaged power supply

An overloaded power supply

A power supply too close to a pedal


Before We Start…


Guitar CableMake sure you have a good guitar cord 

By good, we mean “not broken”.  A simple jiggle test at both ends will usually tell you.  Then consider…


DOD Clean Boost FX10

Boosting your guitar signal

Right away this can strike a lethal blow to any noise that might crop up.  Anyone and everyone should do it.  See Improving Signal-to-Noise Ratio (SNR).  With a hotter guitar signal, you can…


volume-knob-11Reducing your gain

Gain is not free.  The more gain you have, from all pedals and amps, the more noise you will have.  Amps at 11 can give you that extra edge, but you may be just as happy (and quieter) at 9.


So What’s the Deal With POWER SUPPLY NOISE?



Power supplies are most often used by guitarists for powering effects pedals.

The good ones should be quiet.  But even the good ones can cause noise if not used properly.


Now right here, before you $ay “ju$t get a $180 board-mounted power $upply” (we’ll get to thi$), just $low your roll a bit and $ee if there may be a more cost-effective way.


When power supplies are the cause of noise, the noise can be BUZZ, HUM, HISS, or even sound like digital noise (whine).

But noise that occurs when powering pedals is not always due to noise from the power supply itself.

So you should troubleshoot first.


  • Start with no pedals or power supplies, just the guitar plugged directly into the amp.
  • If things are quiet, add one power supply powering one pedal.

To ensure you aren’t overloading the supply (see below), just add one pedal with each supply.


  • If you have more than one supply, add another pedal and supply, and so on.
  • If you add a supply and hear noise, then you probably have found your culprit.
  • To make sure it is the supply and not the pedal, try another pedal on that supply, then try another supply on that pedal, etc.

If you do not suspect the power supply, then try to identify the type of noise you are hearing, and refer to the other articles here in the Guitar Noise Manual.


If you find the culprit is a power supply, it can be for several reasons.



What can cause power supplies to be noisy?


We are going to limit this discussion to noise that is actually caused by a power supply itself.  We will not include other noises that can be generated when a supply is used incorrectly.

You can find out about those other types of noise in articles in the Guitar Noise Manual.  The main ones would be:


Dealing with HUM



When noise is actually caused by the power supply itself, it will usually be one of the following:


A noisy power supply model


You must check to see if your power supply is designed to be quiet for audio, and comes from a reputable pedal (or supply) maker.  If you have a generic power supply made for electronic gear, then that could be the problem.


power-supply-tech21-dc-onblackYou should always use quiet designed-for-audio power supplies from reputable sources, like Boss, Dunlop, Fulltone, etc.

A real ground-isolated Class 2 Transformer is best.  The simple ones are known as “wall warts”.  Those we have tested are as quiet as a battery!


Please note, a real transformer will be heavy and bulky.  This is why they are referred to as “wall warts”.

Transformer Isolation PowerBut a real transformer is the only way to fully isolate and prevent ground loop hum.

As with all power supplies, a wall wart will have a current rating, which tells you the maximum current the supply will deliver without noise.

For standard pedal-audio wall warts, this is usually no more than 200 mA (printed on the label), which will power 4-6 typical 9V stompboxes.


NOTE:  PedalSnake’s 500 mA SnakePOWER supply is an exception.  See below.


You can get lightweight “high current” pedal power supplies that deliver 1000mA or more.  But a real “heavy iron” transformer is the only type power supply that will truly isolate and prevent ground loops.

In general, a good wall wart, with its isolated transformer, usually exhibits quieter operation than the high-current supplies (at least those we have tested).

Most of the time however, there is nothing wrong with using high current supplies.  But if you play high gain, you may notice a bit less noise with a real isolated transformer.


A damaged power supply


Even if the noisy supply is a good brand, and it works, and you seem to be using it properly, it could be damaged in a way that makes it noisy.  In this case, you just need to replace it.


The one thing you can do to ensure long life of a power supply, is to not overload it by putting too many pedals on a power chain.

Drawing a lot of current from a supply will cause it to run hot, which will shorten its life.  It may not die immediately, but noise filters or other components could be damaged.

To ensure long, quiet life of a power supply, you should know its current rating (in “mA”, printed on the label).  Then try to not exceed 50% of that, 75% at the most.

How do you know how much current your power chain is drawing?  See


This leads us to…


An overloaded power supply


Power ChainLike a power supply not designed for audio, an overloaded supply can cause HUM or BUZZ (or other nasty sounds that we have no name for).

If you are using a power-chain, start removing pedals from the chain, and see if the noise subsides.

100 mA Current Rating
100 mA Current Rating

If it does, you may have been exceeding the rated current draw for that power supply (printed in “mA” on the supply).  You can add another supply to ease the load on the first one, or upgrade to a supply with a higher current rating.

See Power Chaining if Fine (When Done Right).



It is hard to know how much current your pedals really draw.  A 9V pedal (that has a battery option) can draw as little as 1 mA, or as much as 75.

If you don’t know the actual current draw (and you probably don’t), we say to assume 25 mA per pedal.  This is a good average to use when adding up the mA draw of all your pedals.

If you want accurate info about current draw, has a site with The Power List, which is fairly extensive list of pedals and the mA each draws.

Or you can measure the current, or have a tech try to do it.  Stinkfoot is happy to report any new info you discover.


With this mind, you should not come too close to the current rating of the power supply, even if it remains quiet.  The mA current rating is just the maximum it can deliver, like the horsepower rating on a car engine.

A good rule of thumb is stay in the 50-75% range, or less.  This means 4-6 average stompboxes on a 200 mA supply.  Then the supply won’t heat up so much, and will last longer.


But 4-6 pedals is not a lot.  This is why PedalSnake decided to offer SnakePOWER.  At 500 mA, the 9D120 SnakePOWER supply has the highest current rating of any single-output 9VDC isolated Class 2 Transformer.

This is enough juice to easily and quietly power 15-20 typical 9V pedals.


Please know, PedalSnake will always be customer friendly.  We try to make life easier for guitar players, not exploit them.  We do not promote myths, we dispel them.  We do not promote wall warts because we sell SnakePOWER.  We sell SnakePOWER and promote wall warts because when used properly, they are the best, most cost-effective solution for having quiet power in your rig.



A power supply too close to a pedal


It is a simple trick to filter electrical noise out of a power supply.  These filters do not cost very much.

But radiated noise is another matter.


wall-wart-noise-demoAny power supply will emit a certain amount of electromagnetic interference (EMI).  When placed to close to an effects pedal, you can hear the effects.

At the PedalSnake Channel on YouTube, we demonstrate this.  At about the 0:35 mark in P-Lines and Power, you can see and hear what we are talking about.


There are expensive pedalboard-mounted power supplies available now, which are designed to be quiet near pedals.  They employ toroidal transformers, which radiate less EMI.

But wall warts can be just as quiet when used properly.   See Do I Need An Expensive Power Supply?


Author: Jody Page

The president of PedalSnake and a member of NASA's Space Foundation Hall of Fame, Jody is a lifelong pro guitarist and electrical engineer with special training in noise reduction. He has spent years in the trenches searching for better tone and better ways for guitarists to approach their craft. His passion is dispelling myths and hype in the guitar industry that seek to exploit our pocketbooks, as well as making entertaining observations about other music-related topics.

8 thoughts on “Dealing with POWER SUPPLY NOISE”

  1. Hi Jody,

    I wonder if you could help with a noise problem I’m experiencing?

    I have been having an issue with my guitar/rig for the past 4 months and it’s driving me crazy. I can only describe the problem as an intermittent loss of signal/distorting/farting issue. One minute my clean sound is nice and sparkly then it almost ‘fades’ (it is not a sudden change) to something more ‘gainy’ with loss of clarity and attack. At it’s worst my clean sound sounds like a cheap distortion pedal. Oddly, on a distortion setting the opposite is true – less signal and gain. It is like the signal is being degraded in some way (interference?). Also, the dynamic range is much greater – when I play lightly it is barely audible and when I dig in it goes very loud and distorts/farts. When I turn my compressor on (applied immediately after the guitar) it helps an awful lot, salvaging the gig for me in most cases. 

    It is totally random, comes on slowly (so you don’t notice it immediately) and only ever seems to happen on a gig (I have ran my rig for hours in the shed at home on numerous occasions and can’t seem to replicate the problem). With regards troubleshooting, so far I have…

    – Ruled out the amp (I have had the amp checked/serviced and have experienced the problem running a different amplifier)
    – ruled out all of my pedals (I have my pedals checked and the problem happens with just the guitar and amp)
    – ruled out the guitar lead and speaker cable (it happens with other leads)
    – I have ruled out the guitar (as the problems happens with my second tele) 

    Other info: It happens on all pickup positions, on both guitar amp channels, it is not my ears (the guys in the band have heard it!) and it is not anything to do with mics or monitoring. 

    Pretty sure I’ve ruled out the signal chain, as I’ve swapped everything out numerous times.

    Only thing I can think of is that there is something at a gig (amd we gig at a differnet venur each week) which is emitting a signal which is interfering with my guitar? However, the noise doesn’t confirm to any standard emi symptoms etc…

    Here is a link to video of y hje problem (this is my clean tone):

    If you have experienced anything similar I would be very grateful if you could give me a shout. At the moment gigging is pretty annoying, to be honest! 

    Thanks in advance 

    1. Your problem is intermittent. These are difficult to solve. Something may seem fine when tested, but still fail. It could be pedal, cable, power, amp. Anything. When they are most difficult, they are caused by slight temperature changes. So it could be the amp, which has the highest temp changes. Touching, bumping, wiggling connections can reveal things sometimes. How often does it occur? The less frequent, the more difficult. You may just have to start with guitar and amp, nothing else, and play until you are satisfied that it is OK, then add one component at a time and repeat the process until you find it. Yes, time consuming! Is the video an example of the problem? That sounds pretty good though! Are you saying that is supposed to be your clean sound, but it is not clean, and that is the problem? If so, that seems like the amp. Does it have a clean and a dirt channel? Does it have a foot switch to switch channels?

  2. TLDR: Can dramatic undersupply of current (500 mA wallwart powering pedals with 800 mA current draw according to cause permanent damage to my pedals, or will the wallwart/daisy-chain cable break before any pedal component damage occurs? I’ve probably run this faulty setup a total of 10-15 hours before I realised how badly undersupplied my pedals were with my current wallwart. Cheers!

    Thanks so much for this site! I’ve found it very useful over the years in choosing guitar gear and making sense of the electronics of power supply. Back in 2012 I bought a pedal snake and a daisy chain cable and have been powering all my pedals using a single Zoom wallwart since! I find the PedalSnake method very clean and elegant.

    Recently I bought a new digital pedal (Digitech Trio+). Under the strain of studying for my PhD (and excitement of a new pedal) I had a moment of carelessness with my gear, and simply plugged this new pedal onto my daisy chain without properly checking whether my power supply could cope with the new pedal. After checking the current draw of the Trio + on (450 mA) I now realise I have been playing with a setup that well exceeds the capability of my 500 mA wallwart. My pedals in total draw more like 800 mA (based on

    The setup has been running ok, but with some notable additional audio noise, and I also noticed the Trio + was restarting itself randomly sometimes. This was partly due to a faulty plug on my daisy chain, but after careful additional testing I now realise the random restarts and additional noise were also being caused by the excessive current draw.

    I was wondering how likely it is that running this setup with dramatic undersupply of current has permanently damaged my pedals? They all seem perfectly fine individually but I’m terrified I have permanently damaged some of their components. I probably played this way for a total of 10-15 hours. Cheers!

    1. While it may be possible in some extreme cases, it is unlikely you would damage pedals by under-powering them, but you may shorten the life of the power supply by trying to draw too much current. (Using a supply with the wrong voltage or polarity is more likely to damage a pedal).

      Power supplies have a current rating (in mA or A), just like cars have a horsepower rating. And, similar to a car, if you use the max power for a long time, the supply will run hot and have a shorter life.

      Other than running hot, all that happens is you get noise. Most supplies make an obvious obnoxious noise when current draw exceeds the max.

      Are you sure you are drawing too much current from your supply? Stinkfoot gives good data on pedal current draw. If you got all your current data from there, then your estimate is probably fairly accurate, and your supply may be somewhat tolerant to over-currenting. But beware, most folks confuse current draw with max current ratings. These are always printed on supplies. But sometimes they are printed on pedals too, which is usually telling you what size power supply you should use, not the actual current draw. So it is possible you aren’t drawing as much current as you think.

      And yes, pedals can act flakey if a supply is overloaded. Over-currenting a power supply can lower the voltage and add AC components which pedals don’t like, so they could behave badly, turning off and/or resetting and such.

    1. You shouldn’t get more noise. It may be that the power supply is bad, or maybe it is just a noisy supply that somehow is noisier on the GT500 (unlikely). That pedal only draws 14mA, so over-currenting can’t be the problem. I know Dunlop makes an 18V DC supply (ECB004) that used to be rated 150 mA max It is a true isolated Class 2 Transformer (generally the quietest types). I see now they make these with 500 mA rating, which may not be an isolated transformer. Your 2000mA supply, to be rated at that much current, is almost certainly not an isolated transformer, and the 500 mA version of the ECB004 may not be either. So try another supply, with the older 150mA version of the ECB004 being the best bet.

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