This is a repost of an article I wrote a couple years ago.
I have often been asked to explain the “daisy chain," so here is my best attempt at explaining it in the simplest terms possible.
There is little bit of math in this but it is VERY basic. Don't let it scare you!
If you’re unfamiliar with the term "daisy chain" it is a nick-name for a group of “male” power supply plugs, linked together so that they allow you to power a handful of pedals from one single power supply. Often, the chain’s main source is the extra female jack on the good ol’ tuner pedal. While the daisy chain is a great and economical solution for many players, there are some things that need to be considered when using one.
Milliamps: Without getting into a bunch of tech-talk, the amount of milliamps or “mA” is very important. Aside from making sure your “wall wart” is the correct polarity, regulated, and 9V (for most FX), the amount of mA’s (current) is the next most important number. To save yourself having to figure out the polarity and “regulated” part, it’s best to stick with any of the usual power supplies specifically made for effects pedals.
For an example, let’s use a garden-variety 9V power supply you’d get at your local music shop.
A typical power-supply will give at least 300mA. Just look on the box or power supply itself and it should be listed but we’ll use 300mA for our example.
Here’s a common question: “How many pedals can I power with my daisy chain?”
The simplest answer is that your power supply could care less if you have 1 or 100 pedals, as long as the mA's aren't exceeded. Overdrives and fuzzers don't need much juice to keep them happy. A Boss DS-1 for instance (the old faithful orange distortion) is only going to suck around 4mA. So in theory you could run 75 of them off one output! Obviously this would be silly, not to mention noise issues and such.
However, it’s not uncommon for a digital delay to use around 65mA or more. That’s more than 15 times our boss distortion. Theoretically if you had four delays, you’d almost be using all your little wall-wart can give. Add to this the rule of thumb that it’s a good idea to leave an extra 75-100 mA overhead just to play it safe and we’re talking around 200-225 mA for our example. Now, with the higher amount of juice the delays need, and our 75-100mA safety buffer, our math has changed in a big way!
(BTW, the 65mA approximation for a digital delay is just that... an approximation. Check the user manual to find out your specific pedal’s draw).
To keep things simple, lets say they’re all the same pedal, drawing 65mA.
Now we’ve got:
300mA - 75 (for safety) = 225mA
225mA ÷ 65 = 3 digital delays (3.5 actually but I haven’t yet come across half a delay pedal).
If we had all Boss DS-1’s pulling 4mA each we get:
225mA ÷ 4 = 56 pedals!
Quite a big difference. To figure out a mix of pedals, it’s just simple addition.
Two delays and two DS-1’s:
65 + 65 + 4 + 4 = 138. Well within the safe zone for our supply.
One caveat: If you’re using a tuner pedal for your daisy chaining, the tuner itself must also be accounted for when totaling your mA’s needed.
So what happens when one exceeds the power supply’s limits? A nasty hum and a fried power supply most often.
I hope this clears up some of the confusion involving the use of daisy-chains on your pedal board. IMO, daisy-chains are fine for very simple set-ups involving four pedals or less. Beyond that, it may be time to invest in a VooDoo labs, Fuel Tank Jr, or similar quality isolated output power supply.
Matthew Holl/Owner, Wren and Cuff Effects
*Please note that this article does not address vintage style pedals requiring (+) positive tip adapters. Any pedal needing to see a positive ground CANNOT be daisy chained with standard "boss-type" neg-tip adapters (which 99% of effects use). Bad things will happen if you do this.