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No transformer, no noise...?
In the old days, the only way to build a AC->DC adapter was by using the trusty transformer/rectifier combo. These days, we are starting to see more and more switching (also known as "digital switching") type adapters. Examples of this new breed are Godlyke Power-All, Visual Sound 1-spot, Diago Powerstation, PowerPad and EBS AD-9, among others. Now, I'm not totally up to speed on the inner workings of these power supplies, but I do know they don't use traditional transformers (the traditional way). The benefits are more power from the same (or smaller) size package, the potential to be used all over the world (most of them will work with anything between 90 and 250 volts in) and potentially cleaner power. But this doesn't mean that your rig will be forever free of noise. Not by a longshot...
Transformer adapters
With traditional transformer adapters, there are two potential causes for noise - EMF and ripple.
- EMF is simply an electromagnetic field emitted by the adapter itself, which can be picked up by sensitive pedals (wah pedals are notorious for this) and badly shielded signal cables. The only remedy here is to physically move the adapter away from the pedal/cable that is picking up the noise.
- Ripple can be described as leftover AC that the rectifier bridge didn't quite straighten out. I won't bore you with the technical details, but suffice to say that the DC voltage that comes from the transformer/rectifier unit will have some remnants of the 50/60Hz AC, which presents itself as slightly choppy DC voltage which undulates at twice the frequency of the AC voltage. This will, if left alone, result in a low frequency hum in your gear (at 100 or 120Hz, depending on what part of the world you're in). Decent-to-good adapters have filtering capacitors that "eat up" the ripple - technically, they charge when the voltage is at its peak, and discharge when it's at its low point, thus filling out the gaps. Most pedals have additional filtering as well, which seems to do the trick. Not-so-good adapters (quite often the "universal" ones you buy at Radio Shack or similar electronics outlets) have too little filtering inside them, which makes it up to the individual pedal to cope with the ripple. Sometimes that's good enough, but plain common sense says it is best to do as much prevention as you can at the noise source, and then use whatever filtering the pedal manufacturers have added as a last defense.
Switching adapters...
...will of course produce EMF just as transformer adapters, but they are just as easy to move around, so that shouldn't be a problem. The selling point for this type of adapter is rather that it doesn't produce any ripple, which would be great news... if it was true. I don't pertain to understand the technology completely, but from what I can gather they seem to switch the AC frequency outside the audible range, which produces a ripple in the 44kHz region, instead of the 50/60Hz we're used to. This means that you can't hear the ripple. Sadly enough, some pedals do pick it up, and then some. What seems to happen is that with some pedals - mostly digital chorus/flanger/delay/reverb pedals, but it can happen with their analog counterparts too - the ripple frequency clashes with the clock frequency. This clash presents itself as a steady high-pitched whine, which in some cases increases in pitch and volume as you turn the pedal's delay time up. Not nice at all. In all the cases I've come across where this has happened, the only remedy has been to replace the switching adapter completely, bringing in the trusty transformer adapter instead. By the way, in every case, the regular Boss PSA adapter (note: I'm talking about the old transformer-based PSA, not the new switching type PSA-120S) did the trick.
I keep hearing reports of people who just before their switching type adapter (usually a 1spot or Godlyke, as they are the most popular so far) died, they heard a loud crackling noise through the amp. For me, that's a cause for worry - at worst, with a regular transformer based adapter you might get a loud humming noise (when the voltage regulator gets overloaded and is about to fail), and then nothing - once the voltage regulator has failed, it will not pass any power at all. But when switching adapters fail, they tend to fail spectacularly, and it's not uncommon for them to take the pedals with them. Ever heard of people's mobile phones exploding while being charged? The switching type adapter was originally designed to be used for mobile charging and as a laptop power supply...
I've also seen several pedals being damaged by a switching power supply pushing in far too much current, even though it's nothing wrong with the power supply itself. This isn't supposed to happen - the pedal is only means to draw the amount of current it needs - but it sometimes does anyway. If something goes wrong in the pedal, causing the power supply to put max out, the insane amounts of current these supplies have on tap (1700mA for most of them, aside from the Diago which can dish out 5000mA) will melt any protection system your pedals might have. They are simply not designed to deal with this much current. I found the pic on the right on the web (if it's yours, and you want credit, contact me), but I've seen a few of these burnouts myself as well. Of course, as the initial problem was in the pedal, this can happen with a Boss PSA as well. The difference is that the Boss tops out at 200mA, a relatively low figure. The Boss can not power as many pedals as the switching type supplies, but neither can it do as much damage!
Boss recently released a switching version of their PSA adapter (PSA-120S), and I don't know yet if Boss intends to discontinue the regular PSA adapter, but it seems likely that they will. If they don't, I'd take it as admission that there's something about the switching technology that isn't kosher for all pedals. In any case, I might just buy up a few of the regular PSA adapters, to be on the safe side. =)
Now what?
So... while switching adapters do have their merits - high power from a small/light package, for instance, to say that they will not produce any noise is simply not true. There are instances where they not only allow noise, but actually cause it. If you have a digital delay or reverb pedal that whines when powered from a switching adapter, you can argue all day about wether the pedal or the adapter is to blame. The fact remains: You want to use the pedal - that's why you bought it in the first place, right? - so the adapter will have to go. It's as simple as that.
Personally, I never let any type of digital switching adapter near my rig - I don't care how many people on internet forums say their 1spot or similar works great. I still give them a very wide berth - partly because of the whining noise (my DanEcho and Voodoo Lab Tremolo simply goes nuts when I power them from an adapter of this type) and partly because of the potential damage they can cause. I'd rather have a fault in one of my pedals blow the fuse and voltage regulator in the adapter, than melt the insides of my pedals... I stick to transformer-based power supplies, and have never had any trouble with any of my pedals. Case closed. For me, at least.
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