A power supply (or wall wart) takes the AC current that comes out of your venue’s wall and converts it into a nice steady dose of DC (Direct Current) for your pedals. It’s important to choose a power supply with the right voltage rating for your pedals.
Some power supplies come with daisy chain connector cables that expand the single output to multiple pedals. However, it’s recommended to use an isolated power supply for best results.
Voltage
As the name suggests, a guitar pedal 9v power supply will provide you with regulated voltage for your pedals. This eliminates the need for multiple 9v batteries (and all the hassle of changing them) in your pedals. This also avoids over-voltage which can damage some pedals and cause a buzzing sound.
Regardless of how many pedals you have, a good power supply will keep your voltage consistent and within the minimum and maximum range specified by each pedal’s manufacturer. The stompboxes on your board will also thank you for the consistent voltage as it’ll help reduce humming and other annoying sound issues caused by voltage fluctuation.
While you can get away with a wall wart and a daisy chain for most analog effects, digital pedals like the Line6 HX Stomp and Strymon TimeLine will require isolated power. These types of power supplies use large, toroidal transformers to isolate each outlet for your pedals. They tend to be the most effective at rejecting hum introduced by noisy outlets, but their larger size can make them less portable.
If you have a lot of pedals that require isolated power you can opt for a dual output power supply like the 1 SPOT PRO CS7 from Strymon or the Eventide PowerMAX. These supplies provide two sets of outputs that can each deliver 500mA of current. You can expand the number of outputs on these units by adding a current doubler (like the Walrus Audio Swell) which will give you a total of 10 additional outlets.
Most pedals have a power requirement specified by the manufacturer which is usually printed on or near the power input jack. This will indicate a required voltage which should be noted in your planning chart. Some pedals may be able to run on slightly higher or lower than their recommended voltage, but this is usually by design and can affect the tone and dynamics of the effect.
While you’re at it, you should also note the polarity requirements of your pedals as each DC pedal has two power rails, a negative and a positive. This is typically indicated by a graphic symbol on the plug or by a label that states “center negative” or “center positive”.
Current
While the voltage of a power supply is important, the current or how much it delivers matters even more. Every pedal has a maximum mA (milli-ampere) current draw that it is designed to power up and run at, and the max mA varies from pedal to pedal. Always check the specs on your pedals to find this information, and be sure to add up the total mA of all of your pedals so that you know whether you need a small or large power supply for your setup. Pedals that require more mA than your power supply can handle will still turn on, but they may not work as well as they should and they might burn out the electrical components inside of them over time.
For this reason, you should never mix-and-match your power supplies or use the same power adapter for all of your pedals. Trying to power up a pedal with more than its rated mA will not harm it, but it can cause the stompbox to burn out or fail, and it may also damage the power supply.
Fortunately, most pedals will work with any compatible power supply with an appropriate mA rating. If you are worried that your favorite pedal might not be able to run on a standard power supply, many manufacturers have designed their own wall warts or power bricks with mA-specific outputs that are guaranteed to be compatible with the pedal.
Power supplies and wall warts convert the AC from your home or venue into DC power for your pedals. They also include capacitors to smooth out the current. This process is not perfect, and some pedals respond to the dips in the current with an undesirable sound that is referred to as power sag. Pedals like fuzz boxes can often be made to sound better by dialing down the power supply’s output voltage to reduce this effect, and some power supplies have this feature built-in.
Some power supplies, including those from Strymon and Cioks, have outputs that are isolated from one another so that you can daisy-chain pedals together without worrying about the polarity or current requirements of each individual output. This is especially important if you use pedals that have very different power requirements, such as a high-gain distortion and a clean boost.
Isolation
A power supply takes AC (Alternating Current) from your house/venue and turns it into a nice steady dose of DC (Direct Current). The AC power runs through a transformer to reduce the voltage, then through a rectifier to convert it back into DC. This DC is then pumped into your pedals to power them. Power supplies are a great choice for powering your effects because they offer clean reliable DC power and don’t introduce the audible 50/60 cycle hum that you can hear with batteries.
Most power supplies have a number next to their outputs which indicates the maximum current that outlet can deliver – in milliamps. You want to make sure your pedals’ mA requirements match this number. If you have a pedal that draws more than the supply’s mA rating it can cause the power supply to run hot and shorten its life. It can also cause erratic behavior or even damage the pedal.
The better power supplies have isolated outputs. This means that if one of your pedals draws more than the output can handle it will not interfere with the other outputs on the power supply. This will also prevent ground loops which can cause unwanted noise in your signal chain.
Pedalboards with more than two pedals often require an isolated power supply. For example, if you have a Boss DD5 and a RAT2 that both draw more than the DD5’s mA rating, it is important that they be powered by different outputs on the power supply to avoid potential problems.
If you’re looking for an isolated power supply check out the Joyo JP02. It offers 10 filtered outputs, each with its own isolated current tap at 100mA and has overcurrent protection and bright blue LEDs to help prevent short circuits.
Power supplies are a great choice for pedal boards because they provide clean reliable DC power and eliminate the need for messy daisy chains of batteries. However, if you’re not careful when choosing a power supply it can introduce unnecessary noise into your pedal chain that can affect your tone and even ruin your sound. To ensure you’re getting the right power supply for your needs, keep these 6 things in mind when buying one:
Noise
The power supply takes the high AC voltage from your wall and transforms it into the nice steady dose of DC (Direct Current) needed to run your pedals. This is done with a transformer which reduces the current to your pedal’s required rating and then a rectifier that converts the current back into DC. The result is a clean, steady current that’s safe for your pedals to use and won’t damage them or wear out the internal components of your pedal.
If you have multiple pedals on your board it’s common to daisy chain them together with the output from your power supply. This works great with 3 or 4 analog pedals but can quickly turn into a problem when you start adding digital pedals that have very different voltage requirements. The issue is that each pedal in the chain can create their own slight perturbations on the power supply which can be picked up and amplified by all the other pedals in the chain.
Isolated power supplies help prevent this from happening by providing each outlet on the power supply with their own individual transformers that provide each pedal with its own isolated voltage. This also helps keep the total current draw under each power supply’s maximum rated amount which can help avoid pedals not turning on, or even worse, having the power supply burn out from excessive load.
Depending on the type of power supply, some will also have each output with its own voltage regulator that can help prevent noise and interference between pedals. This is particularly useful with effects that require a specific voltage like wah pedals which can induce audible 50/60 cycle hum when placed too close to a traditional transformer-based power supply.
If you are struggling with an issue with a specific pedal or a whole pedalboard, it’s often best to work through each component and power source one at a time, starting from the top of the chain down. This can often shed light on where the issue is stemming from and allow you to solve it before it becomes a bigger problem.