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I have a Boss BCB 30 pedal board with daisy chain. I have three pedals: TU2, CS3 and DD3. I was planning to pick up an universal power adapter I can use with it. I'm not that literate coming to electronics, so what should I look for when I pick a power adapter for this purpose?

  • I'm pretty sure Boss makes an adapter to power their pedals. Since you are happy with the Boss line, you might just continue down that road. – Todd Wilcox Oct 20 '15 at 19:44
  • Yes, I know their Boss PSA adapter would be a safe pick, but that's not my question. :) – janlindso Oct 20 '15 at 19:46
  • I made it a comment for that reason. Maybe if you mention why you aren't happy just getting the Boss adapter(s), it will make your question clearer. Without more information, it's tempting to recommend you simply look for a power adapter that will be compatible with your pedals. What else do you need? – Todd Wilcox Oct 20 '15 at 19:49
  • I need an adapter to be used for several different purposes rather than buying 10 different adapters that is pricy because of brand. – janlindso Oct 20 '15 at 19:50
  • Ok, that helps. So you want to be able to power other pedals in the future besides just the Boss ones you already have? – Todd Wilcox Oct 20 '15 at 20:00
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It's best to have the pedals picked out and/or purchased before finding a power supply for them, because there are some strange power requirements out there and it's hard to know what you need until you have it. That said, there are some power supplies that give you options to change the settings for one or more outputs to give you some flexibility.

There are some (usually boutique) pedals for which there are no power supplies that can power them with just a straight connection. The MuFX Tru-Tron is just one example.

Power for a pedal needs to fit three criteria:

  • Whether the power is AC or DC must exactly match
  • The voltage must exactly match
  • The current provided by the power supply must be equal to or greater than the current needed by the pedal

The most common power requirement for a guitar pedal is almost certainly DC, 9V, and 100 mA or less. So, most power supplies either only supply that kind of power, or have most of the power outputs designed to supply that configuration.

One more thing you may very rarely have to be aware of is the polarity of the power needed by the pedal. As far as I know, the only pedals likely to have reversed polarity are those with germanium transistors (usually vintage style fuzz pedals). You can power those with either a polarity-reversed connection or with an isolated power output or dedicated supply.

When looking at a device that can power multiple pedals, some of them will have a dedicated amount of current for each power output, and others will have a total amount of current that they can handle for all the connected pedals. For the ones with individual current supplies, each supply must be enough for the pedal plugged into it. For the total current style, the sum of the current needs for all the connected pedals must be less than or equal to the total supply.

Beyond having the power requirements met, there are some extras that the more expensive power supplies may offer. Isolated outputs are nice for keeping pedals supplied correctly and allowing for reverse polarity pedals. Other add-ons include more outputs, unusual power options, accessory outlets, voltage sag (to simulate old batteries), mounting brackets for rack or pedalboard mounting, etc.

The information above is for the output of the power supply, to match the input(s) of the pedal(s) that will be connected to it. The input for a power supply should match the building's power outlets. Power supplies should either have a sticker on them or a page in their manual detailing the input and output parameters. Here is an example sticker:

enter image description here

Notice that the input is AC and the output is DC. Also note that it says "0.5A" instead of "500 mA", which are two different ways to say the same amount of current is available. The polarity is shown by the circles and lines right under the output line. The polarity diagram on this sticker indicates standard polarity, often called "tip negative". This power supply could supply at least five standard pedals that require standard polarity 9V DC power of 100 mA or less.

  • Thanks for a very informative answer. I thought I had followed these criterias on my setup (in my question), and got myself a 9v 1000mA AC power adapter with reversed polarity. But I only got it working when connect to only one pedal, but not all with daisy chain. – janlindso Oct 20 '15 at 20:52
  • Are you trying to buy something different or figure out why the one you have is not working? If it works with one pedal then the output is certainly DC, even though the input is AC. Any power supply should have both input and output specifications. I'll add that to the answer. – Todd Wilcox Oct 20 '15 at 20:55
  • I actually got a universal adapter that doesn't seem to work, which should work according to the information I've read about pedals. But unfortunately it don't work, so I got interested in what I may have overlooked. The adapter has IN: 100-240 V, 50/60 Hz, 0,3 A, and OUT: 9 volt 1000 mA, and reversed polarity. According to the PSA adapter, and information given, I cannot see why it won't work. – janlindso Oct 20 '15 at 21:16
  • Most of the DC adapters I ever had to test were negative on the collar, so yeah, "check the polarity": good tip. – Yorik Oct 20 '15 at 21:30
  • @janlindso It might have been better to have asked your specific question, since it seems now like you still don't have the information you wanted. I agree that the daisy chain cable may be the problem. You might check to see if it works with two pedals instead of one or three. – Todd Wilcox Oct 20 '15 at 21:33
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You want an adapter that conforms to the wall plug in your country. In the US, that's 120V.

After that, a quick check indicates that Boss adapters output 9v (or 9.5v; makes sense since they are designed for 9v batteries) and I see photos of most of them supplying 200mA. I don't think most pedals draw anywhere close to 200mA (probably more like 10mA max; the CS-3 manual says 11mA for that one), and the power draw is straight additive so two would be 20mA etc.

The Boss website has one that can supply 9v at 500mA. So the BOSS-branded range off the shelf is going to be between 200mA and 500mA.

Most of the pedals I have actually held in my hand have had the specs on the bottom sticker.

The male-end connector is standardized for voltage as far as I know, so if it fits, and you can see the specs on the brick or in the manual, you ought to be fine. I have a very old one from Radio Shack which is switchable from 1.5v to 12v and has a swappable plug end for each voltage rating. I expect it was in the 5$ range.

So for US: INPUT: standard 120v AC 60Hz OUTPUT: 9.Xv DC 200mA-500mA

  • Just tried a universal adapter with 9v, 1000 mA. Check for correct polarity. I worked for one pedal, but not all through daisy chain. And on one pedal it was more noisy than with battery. But shouldn't it in theory work? – janlindso Oct 20 '15 at 20:43
  • I would suspect the daisy chain. If you have a voltmeter, you can test the connectors by switching the meter to the proper dc voltage range and then putting the positive probe inside the connector tube and touch the ground probe to the outer collar. Transformers are EM noisy, move it away/alter the angle, and try plugging it into the same power strip as your amplifier. – Yorik Oct 20 '15 at 20:56
  • I'll see if I can borrow a voltmeter, but the daisy chain is completely unused from the package, so it should be OK. – janlindso Oct 20 '15 at 21:18
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    I suppose an easy way to test the cable is to simply take the one device that works and plug it into each connector in turn. If the single device works on each connector, then it probably is not a manufacturing defect. – Yorik Oct 20 '15 at 21:22
  • There's no guarantee that each pedal won't feed some AC noise back onto the power line, so a pure daisy-chain cable may pass that noise around; or it could simply be acting as a ground-loop antenna. I'd stick with supplies that have independent output ports. – Carl Witthoft Oct 21 '15 at 19:22

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