Let's be accurate, OK? I happen to know a great deal about the 1Spot in particular and other wall adapters in general, as well as having designed switching power supplies for a living a ways back.
Brian M wrote:i dont have a schematic, but i can tell you the reason why it is smaller than a typical power supply. It has no transformer.
Actually, it does have a transformer. It has a high frequency transformer. The power a transformer can handle is limited by its temperature rise and the lowest frequency it has to pass. By rectifying the AC power line to DC, then switching the DC at a few hundred kilohertz to maybe a megahertz, the size of the transformer needed is vastly decreased FOR THE SAME POWER TRANSFERRED. The isolation transformer in the 1Spot is about the size of the end-section of your thumb.
Brian M wrote:It is becoming a more and more common way of making DC power supplies.
It's not only becoming more common. California has LEGISLATED that all wall adapters sold there must be switching type (based on the required efficiency). This goes into effect this year.
Brian M wrote:Essentially what they do is they use an electronic switch (probably just a beefy transistor with a heat sink) it turns on when the mains power reaches a certain voltage (usually peek) and charges a capacitor. When the capcitor gets to a certain voltage the switch gets turned off. The charge goes to a voltage regulator, and from there you have your voltage output.
Close, but moderately wrong on all counts. As I started with above, what they do is to first rectify the incoming AC power line to either 170 or 340Vdc. Then they use typically a power MOSFET (used to be bipolars, but they're too slow in general) to chop the DC into rectangular square waves which are fed to a transformer. The transformer provides the necessary safety isolation (4kV) between the power line and the secondary, as well as stepping the voltage down. The secondary is rectified to DC again and used as an output. The output is fed to an optoisolator back to the control IC on the primary side for regulation. The circuit regulates itself by the pulse width in the chopped waveform fed to the transformer.
Brian M wrote:Since they primarilly rely on the regulator for their output voltage they will run off a wide range of input voltages and frequencies if designed corectly.
Since they rely ENTIRELY on the pulse width regulation of the IC in the primary side, they can run off a wide range of input voltages, generally 80Vac to 260Vac and still maintain regulation if designed properly.
Brian M wrote:The active switching puts a bit of a limit on how much current you can economically get out of this type of power supply.
The active switching allows you to get vastly more current out of the same size, weight or price power supply compared to a non-switching power supply in all but a few instances. One of those used to be the very small size power supplies. No longer, as the 1Spot and its ilk show. I don't think you can get a non-switching power supply for the same price and size that produces as much power (i.e. voltage x current) as the 1Spot. Switching is the way to get high current and power in small packages with low waste heat.
Brian M wrote:Most of these types of of power supplies have other stuff in them to make sure they turn off if they start to fail, although the earlier onespots supposedly fried a lot of pedals a few years ago. Not sure if they have changed anything.
Unless you're using "onespots" as a generic term like "xerox" for copier and "kleenex" for facial tissue, you are incorrect. "1Spot" is a trademark for the single-AC-plug power adapter sold by Visual Sound. There are other brands, as I mention below that have copied the concept. One very common one appeared less than six months after the company had a booth next to the Visual Sound booth at NAMM.
It is true that some switching style plug in 9V adapters are poorly designed and probably have fried effects. It is not true that there was ever a 1Spot frying epidemic. I know, I work for the company (Visual Sound) and part of that work is to evaluate *every* 1Spot related issue where the adapter has supposedly fried a pedal. We have given some people the benefit of the doubt, and we have had a few die in the field, but overall, the 1Spot has an incredibly (even to me) good track record. It was designed specifically for powering pedalboards over a long design period, and does it very well; to the best of my knowledge, it is the ONLY adapter designed solely for powering pedals, not adapted from some other use. The 1Spot is not perfect - but the statistics show it's very, very good at what it does.
It does it so well that it has of course attracted imitators. Take your own chances with the imitators. It is possible that the imitators inspired what you heard about as fried pedals.
The 1Spot has also been the target of some effects makers blithely saying that the 1Spot kills their pedals. We have investigated a number of these down, provided free 1Spots and technical data for them to do their own tests and also conducted OUR own test on reliability. I believe that all of the pedal makers who have had this position and worked with us have changed their minds and now have no issues with the 1Spot.
We have yet to find a case where the 1Spot, even the earliest ones, wantonly killed pedals. The insides of the 1Spot provide a number of safety measures designed to keep the pedals safe, in fact.
Brian M wrote:edit- also, when i was working in the energy, as these types of power supplys were becoming more common, they were actually causing electrical problems in large office buildings. Lots of fax machines, and computer equipment uses them these days. Since the load the mains power sees is not at all linear the cumulative effect, especially in large buildings (long cable runs) ends up causing a lot of harmonic distortion on the mains power. When this happens, the neutral connections at the breaker box heats up and can start a fire. fun stuff.
When I was working in power supply design, that was indeed an issue, and is a recognized one in the power distribution industry. You don't go far enough. I can't think of a single current-manufacture office machine other than "dumb" stuff like refrigerators and coffee makers that do not have a switching power supply. With California and other places legislating power efficiency, you can assume that the power distribution is simply going to have to cope. However, it's the aggregate of the zillions of kilowatts of switching power supplies doing that, not the 1Spots.
The 1Spot meets or exceeds every standard for safety, performance, efficiency, radio emissions and even power factor issues (that's your distortion/neutral current issue), as well as being the only pedal power adapter I know of that is 100% tested on the power line for working with no switching noise in a high-gain distortion pedal. Every single one is plugged in to power a high gain pedal that's selected for being finicky, and must not produce audible hum or whine. I've watched them do this on the assembly line.
Do you get the idea that you hit a nerve?