Battery or not?
There are two main ways to feed power to your pedals - either with an internal battery or with an external power source. I'll come out straight off and say that the battery option is by far the best - from an electronics point of view at least. By having separate power sources for each pedal, they can all think they are alone and king of the hill. No ground loop hum (caused by the signal getting two ground paths - one via the signal cables, and another via the power cables) and no messy daisy chain cables to set up. But batteries are expensive - if you play a lot, an adapter will pay for itself rather quickly. But if your pedals (or rather, your wallet) need external power or not has a lot to do with how much power they consume - if a pedal eats batteries for breakfast, getting an adapter for it will be economically wise. If a pedal draws very little power, you might be better off running it on batteries even if you get an adapter for other pedals - usually, the less pedals you give external power, the smaller the risk of getting annoying hum and noise. But how do we know how much power they draw? If you still have the documentation (papers/manuals etc that came with the pedal) you might find the information there, otherwise you'll have to ask the manufacturer. Or... you could measure it yourself.
Here's how: You need a multimeter set for DC, mA and a patch cable. Get the pedals' battery out, still attached to the battery clip. Unplug the clip and put it back sideways, so that the negative battery pole still is connected. Plug the cable into the input jack (turning the power on), and grab the multimeter cables (red and black). Touch the positive battery pole with the red cable, and the open connector on the battery clip with the black. The multimeter is now a part of the pedals' power circuit, and will show the current draw.
For scientific purposes (eh?) I measured some of my pedals this way, and you'll find the results in the table below.
| Pedal |
Current draw (bypass/active) |
| Ibanez CS-9 stereo chorus |
9,3 / 10,2 mA |
| Ibanez TS-9 tube screamer |
6,8 / 7,5 mA |
| Boss OD-1 overdrive |
4 / 4,5 mA |
| Boss CE-2 Chorus |
8-8.8 mA (fluctuating) |
| Boss DC-2 Dimension C |
29 / 29,3 mA |
| Boss DC-3 Digital Dimension |
60 mA!!! (stated) |
| Tech 21 XXL |
4,34 / 5,33 mA |
| Voodoo Lab Tremolo |
8,5 / 11,5 mA |
| Electro-Harmonix Big Muff Pi |
3,95 / 3,95 mA |
| Dunlop GCB-95 Wah |
0,43 / 0,43 mA |
| Danelectro DanEcho |
38 / 38 mA |
| Danelectro DJ-14 Fish&Chips |
17,8 / 19,5 mA |
| StinkFoot CloneBender |
1,08 / 4,5 mA |
| TC XII Phaser |
|
As we can see, any differences between when the pedal is on or off are quite small - they can mostly be accounted for by the added current draw of the LED. The biggest difference is in the StinkFoot pedal - its fuzz circuit draws barely nothing when it's just sitting there on the pedalboard, but its yellow LED needs a little more power to be seen than others. We can also see clearly why the Boss Dimension C drinks batteries like a thirsty camel - as if I hadn't noticed it already - it has a current draw that is 7 times that of the OD-1... And - just for comparison - the digital version draws double that. Gulp. In essence, the same battery will last 7 times longer in the overdrive pedal than in the analog Dimension C... But that's nothing compared to the wah pedal... the same battery will last a whopping 67 times longer in the CryBaby than in the Dimension C. No need to mess with adapters for the wah, then... And it also proves that there's hardly any need to modify it to shut the power off when you bypass it - if you have someone do that mod for you, you will probably not recoup the cost for a looong time...
I still want external power - so there!
Ok. I won't hold it against you - even though personally I wouldn't bother with it unless I had my pedals at least semi-permanently set up on a pedalboard. The added inconvenience of having to plug and unplug the power cables as well would be too much. But If you want to (and I will, whenever I get a stable enough setup to build a pedalboard around) there's two ways to go about it. Options, as always...
- "Wall wart" or adapter with daisy chain
- Dedicated power supply unit
1. Adapters...
...come in all shapes and colours and some are good, some are bad. A generic Radio Shack adapter is more likely to cause you grief through hum and noise than a genuine Boss, Danelectro Zero Hum or Switchmode unit, but you might get lucky. You need to decide which pedals you're going to power with the adapter, and know their current draw. Then add the numbers up - the adapter's max current output must never be exceeded! Also, be aware that not all pedals use 9v - some Boss pedals actually want 12v on the adapter input, even though they use 9v batteries. If your Boss says "ACA" on the bottom plate (instead of the more common "PSA"), and it's manufactured before august 1997, it needs a 12v unregulated (ACA) source. If it's manufactured after that date, it will work with 9 volts, but it prefers it to be unregulated.
Unregulated (ACA) and regulated (PSA) are two terms that you need to know about. A regulated power supply always put out the same voltage, no matter the load. A Boss PSA adapter will give all pedals 9v regardless of the total current draw (up to the adapters' max current output). An unregulated power supply will drop its output voltage as the current load increases, which might be the reason Boss decided to use 12v rather than 9v unreg. If you have a Boss pedal that needs the ACA adapter, it's probably an overdrive that doesn't have a very big current draw. As gain effects like overdrive/dist/fuzz are most sensitive to hum from adapters, you might be better off running the ACA pedals on batteries, while powering the rest from the adapter. Just a thought...
- Note: Not all Boss ACA adapters are made equal. Depending on its manufacture date, it is either 12 volts or 9 volts - and you need to know which one you have, and which one your pedals need, if you want to properly feed them. Click here to read more (opens in separate window).
Anyway, the adapter has a plug that fits in the power jack of one of the pedals, but to power more than one you need some means of splitting the power. Enter the daisy chain cable. It's a cable with several plugs on it (in general it has 4 to 6) that starts with a female connector. The adapter plug fits into the female connector, and the other plugs goes in the pedals. Easy!
A major possible problem is hum caused by ground loops. As your pedals will now have contact with ground not only through your signal cables, but also through the adapter cables, you are in danger of creating a ground loop --> loud, annoying hum. There are no rules about these things - you might find that in some rooms you get hum, but in others it's fine. Ok, there's one rule that applies here, and it's the one Murphy wrote. It's usually fine at rehearsal, and when you get to your big gig, the thing hums like crazy... Time to do some woodshedding. Make sure you have batteries in the pedals, and (with your amp on low volume, but loud enough to hear the hum) start unplugging them from the external power. Do them one at a time, and see if you can identify a single pedal that seems to cause the noise. If you find one or two that, when you run them on batteries instead, make the whole chain nice and quiet, consider yourself lucky, and get some spare batteries. On the other hand, if the whole thing still is a mess, and your pedals don't like each other at all, you might have to enter the world of the dedicated power supply.
2. Dedicated power supplies...
...also come in many flavours. Some are more or less a splitter unit (like a daisy chain, but with all the splits inside a box, and a separate cable to each pedal), while others are more involved. The splitter type runs from its own adapter, which means that it receives 9v power and feeds it to the outputs. Some of them are really good - they provide stable power while preventing ground loops - while others are utter crap (since they cost a lot more than a daisy chain, but do exactly the same thing). The good thing with all "splitter" type psu's is that you don't need to fit the whole transformer/rectifier package inside the box - which could be a noise-maker in itself. The bad thing is that you need to know the max current output of the adapter, because you will need to conform to its limits. An example of this type of power supply is the Dunlop DC Brick (formerly known as the Dunlop Juice Box). It has gotten good rewiews, and seem to work fine for most people. Some "powered" pedalboards like the SKB fall into this category - the SKB seems to be relatively well filtered (less noise), while the Visual Sound One Spot and Power All are daisy chains, plain and simple.
At the higher end of the market you'll find units that not only split the power, but also isolate the outputs from each other. This will prevent any ground loops, as the pedals all think they are alone. Clever stuff, and quite pricey. But if you have problems with noise, it might just be the ticket. Some units use isolated groups (like having two daisy chains), so you can partner pedals that can live together and isolate those that can't. Other units isolate ALL outputs separately, which means that unless you daisy-chain several pedals from a single output, all pedals will think they are alone. As always, you need to know the current draw of your pedals, and the max current output of each output/group of outputs on the psu. Good units are the Voodoo Lab Pedal Power 2 (8 isolated outputs at 80 mA each), the ADL Juice Box (not made at this time) and the Black Cat, but there are plenty of them about. A VHT Valvulator will - while its primary function is signal buffering - let you power some pedals as well. It has 4 isolated outputs at 80 mA each. Furman makes a pedalboard with integrated psu that also have 8 isolated outputs.
Check out the Carl Martin Big John (the same as the one on the right, just not the "anniversary" model). The outputs are not isolated, so it could possibly cause ground loop hum - but so would a daisy chain with the same pedals as well. It has more to do with how sensitive the individual pedals (in that particular combination) are to ground loops. But the transformer/rectifier unit looks like it could survive a nuclear attack, and the filtering caps look pretty serious too - I doubt that anyone will get choppy DC from that unit. It can provide a total of 600 mA, from one or all jacks (they are wired in parallel), and uses rca jacks (tip positive) as outputs.
But hey... my Boss TU-2 can power pedals!
No... it can't. Let's put that issue firmly to rest. The TU-2 (and the other Boss pedals with power output) has a link output that will let you daisy-chain from it, rather than straight from the adapter. A forumite at the Harmony Central Effects forum (where I hang out too much) coined the term "power thru jack", and that's just what it is. But it's still the adapter that does the powering... The only difference is that you plug the adapter cable into the TU-2 rather than into a female cable connector, and then you need a special daisy chain cable (as the link output on the pedal is the same type as the input). I've found that often when people have ground loop problems, they disappear when the TU-2 is removed either from the signal chain or the power chain. As it usually sits at the front of the effects chain (where the signal is most vulnerable to picking up hum), to me it seems like a daft idea to pass signal as well as all the power through it...
But if you do use it this way, please note that the TU-2 can only cope with 200 mA output, no matter what your adapter can deliver. If you need more power than that, you need to daisy-chain around it, instead of through it. Just get a regular daisy-chain cable (like the one pictured earlier) and add the TU-2 to it like you would any other pedal. Or... better yet - put the TU-2 in the nearest bin, then go get a good tuner (the TU-12 for instance) or use your ear and a tuning fork. Needless to say, my own experiences with the TU-2 has been less than satisfactory...
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