Power supply for pedals

[R.G.]

OK. Just checking. I thought you said it was working OK. And while the daisy chain cable is thinner that the cable on the main power unit, as I said, the cable on the power unit itself is in fact quite thick for such units. There may be another one with thicker copper wire, but I don't know of it if it exists.

There's another funny thing about copper wire. Flexibility (and with that, immunity to work hardening and breakage) is conferred by making the individual strands inside the cable thinner. House wiring is done with single-strand wire, and it's very stiff. It's also easy to break if it's flexed a lot, because what matters in flexing is not the overall cable size, but the radius of the bend in relation to the thickness of the individual copper strands. To a solid #12 wire, a 1" radius bend is pretty abrupt. To finely stranded wire, it's almost impossible to work harden the wire because the individual strands slip along one another and support each other so that it's hard to get a tight-radius bend on any one of them. #00 welding cable ( I weld a little, for fun) is quite heavy, but the good stuff is almost limp. It's made of many, many strands of very fine wire. It spends it's entire life being bent around. It's not the thickness that keeps it from breaking, it's the fine stranding. That's impossible to see without cutting one open. And the copper composition, especially an annealing step before encapsulating the wire in a vinyl overlay can't be told without some lab work on the individual strands.

Another thing that enters into the wire breaking stuff is abrupt transitions. Wire crimped into a metal sleeve will usually break right at the end of the sleeve, because the sleeve forces a tight bend right there. Inserting soft, gooey stuff to make it harder to bend it abruptly is another way to prevent bends with a small radius compared to the strand diameter. It's the radius of the bend compared to the strand diameter that determines bend sharpness and eventually work hardening and breakage. Another abrupt transistion that doesn't get thought about much is tinning wires. If you tin a stranded cable, the solder wicks up between the strands and turns it solid up to the point the solder stops. There is no soft transition possible. Tinned wires which are flexed often break right at the solder edge, even up in side the vinyl overcoat.

I understand that the daisy chain cable looks thin to you. And it is in fact much thinner than the main cable, the one that's permanently attached to the power unit. But from our other discussion on diystompboxes, I thought you liked the idea of using a separate cable, on connectors, which could be replaced, like the IEC power cables.

With the daisy chain cable being easily replaceable by connectors, it's entirely possible to replace it by the guitar-pedalboard equivalent of "monster cable", super-thick cable that will handle zillions of amps. It might be more expensive to do that, but the magic of the market is that, having seen this conversation, some enterprising young entrepreneur will likely introduce "Godzilla's Daisy Chain", an eight (or ten, twelve...) connector 9V power cable where the wires are half an inch thick, and made out of "oxygen-free, cryogenically relieved linear-crystal virgin copper yada yada".

As I noted, a lot of this comes down to how much can the maker afford and can you afford to buy. For instance; if I got the boss to authorize manufacture of the "Godzilla Daisy Chain", with #14 fine-stranded copper, 1/2" diameter plugs on the power connections to hold the thick wire, and possibly gold-plated connector barrels to make it look fancy to the uninitiated (but really offer no real increase in performance), how much would you pay for that daisy chain?

[Steve Conner]

I'm opposed to the whole idea of running pedals off a switch mode power supply. I had one that injected a nasty hissing noise into my distortion pedals. Although to be fair to RG, I can't remember whether it was an actual 1Spot or some (obviously inferior ) other brand.

I returned it and swapped it for a Sound Lab Power Bank, which is a metal box with a linear power supply inside and a half dozen power sockets all connected in parallel, that costs nowhere near 200 bucks.

What's the difference between EMI and RFI? It's all electromagnetic fields. Neither aluminium foil nor copper tape will attenuate the power frequency magnetic field from a transformer by much. It takes about a quarter inch of steel.

[R.G.]

Historically, it was quite difficult to get the first 1Spots to NOT inject noise. This predated me at the company, but I understand that it took many months of tinkering and adjusting to get it subjectively hum and noise free. I say "subjectively" because no power supply running from mains will be completely mains-hum-free, and no power supply, including a battery, will be hiss free. But batteries don't have switching artifacts or heterodynes with signal. But the then-we polished and refined until we could not hear anything on the worst (in terms of power supply susceptibility) pedals we could find.

We guitarists are kind of stuck with the ideal of pedals running from a switch-mode power supply. Governments world-wide are tumbling to the control-of-the-peasants ideas lying behind legislating against anything that can be construed as dangerous somehow or which makes using "too much" energy easy or even possible. The USA outlawed making and selling non-switching power adapters in the name of energy efficiency. Other countries have too. This was done by specifying efficiency and no-load losses below what a non-switching transformer adapter can do.

One idea we tossed around was making pedalboards run much like cordless drills - have an easily-pluggable rechargeable battery pack that is then made into 9V or whatever by linear regulators. The proto for this was done by shopping the used-goods sales for a cordless drill, cutting off the handle to get the power "socket" contacts, and renewing the battery pack. Works fine; it's a little bit of a PITA to get into a pedalboard, but nothing a few $100K in plastic die-molding wouldn't cure. About a year after we messed with this idea, Sanyo did come out with a rechargeable battery pack for pedalboards, but for reasons I can't fathom, they did it a very odd way that made it even more trouble to use.

I take occasional runs at rechargeable battery packs. I've done several designs, and I'm sure we'll eventually produce one when I hit a good compromise between "tastes great" and "less filling" to subvert an old light-beer advert from the US.

[jbltwin1]

RG brings out a very accurate point about the quality of the cord AND the abuse we put them through. I know people who have used their original 1Spots FOREVER and never have a problem. THey are also the people who take care of their stuff. I personally build my own power supplies but hey, that's me. I also buld mine to be pretty much bullet proff bacause I am NOT very careful and am a clutz at times. My pedalboard is designed to have most of the wiring underneath the lid and the wires are retained by soft plastic clips with no sharp bends. The reason is exactly what RG says-no sharp kinks and and no lost motion. Keep the wires from banging around, back and forth and have no motion. Wire has specs for the number of bends that it will take and being locked up inside a pedalboard banging around the country and sometimes getting cold as hell, stuff gets brittle. Like I said, I personally use a PS that you could charge your car battery with if you wanted but since I build my own stuff, what's it cost? A few caps, a fixed or variable IC regulator, four diodes(full bridge) and a few resistors. Nothing magic there. Oh yeah, and a transformer-forgot! The problem with these are the size. If you are cramped for size, the 1Spot is GOLD.

[Steve Conner]

RG: Are you saying that Visual Sound actually put some design effort into the electronics inside the 1Spot? I assumed it was just a stock 9v switcher from some Chinese OEM's catalog, and maybe you shopped around to find a quieter one.

[R.G.]

Yep. A stock switcher from an OEM's catalog is what I *think* the others are. We do have them OEM'ed, but I've personally met with and discussed tinkering the insides of the 1Spot with the design engineers in the companies that make them.

We (the company, now; it predated me) first asked an OEM for a switcher. The boss tested it, and it was OK, but had hum and whine issues. Back to the OEM. No good results, so enter OEM #2. Better, and more willing to work with the company on it. It actually took six? nine? months of back and forth, with each new prototype played by guys who make a living playing guitar and listening for better or worse by A-B-Z-ing them with other adapters and batteries. The insides were substantially changed over that time, tinkering with speeds, feeds, filtering, etc. to clean up artifacts. When the 1Spot went to market, it had been worked on by both critical listeners and some engineers I have come to respect (don't get me started on engineers, either ) to get it right.

Just to make sure, 100% of the 1Spots coming off the line are listening-tested using an especially power-supply-prone distortion pedal (thankfully, from another manufacturer! ) ; we pay extra for a person to sit at the end of the line, plug them in and listen to them, rejecting ones where audible artifacts can be heard.

And it's been worked on over time. The current version is about number five. We do actually listen to comments and complaints. Some complaints are -- well, less than substantial, if you get my drift -- but we get valid complaints and pretty much anything that can be replicated and a fix found for is fixed. One of the updates was to put that heavier power cord from adapter to plug in, just for reliabilty. Here are the two pictures from the other forum; they're not my pictures, I just copied the links. Notice the change in scale/magnification.



This process is one reason I'm a little sensitive to the use of "one spot" as a generic term for plug-in 9V adapter. We've actually had "customers" return other brands of adapters to us for repair/replace/refund. We do work at it. There are much cheaper ways to do this. But quality is achieved the same way, no matter who builds it. You do a quality design, a quality job of integrating (not 'turning over'!) the design into manufacturing, test the result, then *keep on* testing the results and tweaking/tinkering as needed to keep the quality up. It's not a one-time thing.

I really *did* have to sit through education sessions on "how the Japanese do it" to get quality products back in the -80s.

It's funny though. The 1Spot was presented to dealers first at a winter NAMM show one year. Another company whom I won't name had a booth across the aisle from Visual Sound. Four months later they had their work-alike on the market. They sold them for some years, but have now quit, I believe. We got some of them as "defective 1Spots" in the shop, so I know what is in them; well, OK, what was in them at the time. They were in fact identical to one of the several OEM 9V supplies we bought and keep for reference.

It is not simple to get a quiet switching power supply for audio purposes. I've been there. The easy approach is to, as you say, avoid switching power for audio. However, we're all kind of stuck with it until we can convince our nanny-state governments to leave us alone.

[Steve Conner]

Well, I guess mine wasn't a genuine 1Spot then!

I remember that it had several different coloured adapters, and I don't recall the 1 Spot sticker on the case.

[R.G.]

I'd be the last one to say that 1Spots are perfect. But we do work at it.

[dumbassbob]

Part sound quality, part because they believe the advertising.

A small, cheap plastic (-cased) plug in transformer can give you 500ma. But unless it's carefully designed for pedals, it can also give you bad hum in your pedals, and may not be the right voltage. You need the right voltage and enough current.

Most pedals specify 9Vdc, largely matching what a 9V battery gives when it's new and fresh.Some pedals *tolerate* higher voltages. A few, mainly decades-old ones need lower, as low as 1.5V or 3.0V. some digital pedals need large currents and may need 9V*AC*.

You take a chance on killing your pedal if you don't give it the right voltage. If there is enough current available, it will take only what it needs. That's why you need to be careful. Not all "9Vdc" pedals are alike. Some are 9V only at fully current, and some are not filtered at all.

However, there are $20 power supplies specially designed to mimic an inexhaustible battery, and power tens or (literally!) hundreds of pedals while doing it. The company I work for does one of these. There are other brands. Why the gulf between these and the $200 many-output power supplies?

Two reasons. First, there are some pedals which need negative 9Vdc, not positive 9Vdc. The best illustration is the Fuzz Face and other germanium PNP pedals. It is handy to have an isolated output that can do this, although there are less-than-$200 solutions to the same problem. Second, there are some fairly rare situations where having isolated power supplies can make for less overall hum; the makers of $200 power supplies obviously will thump on these situations hard and long.

I show how to do a multi-output power supply on my personal web site, geofex.com. Look for the "Spyder". The whizzo isolated power supplies are largely flourishes and enhancements on that theme. I probably ought to go do the detective work to see if the whizzos predated the Spyder, or the other way round. I don't remember them before I published that, but then I was not looking.

Questions?

thought this was a good post to review again

[TransLucid]

I used the following approach, and it's been working well for me for a number of years:

1. Find an old wall wart supply that outputs around 12VDC (I used a Sony 120V/9Vdc/1A unit). Cut off the plug, but leave some wire.
2. Make a regulator using a 9V 3-terminal chip (they're cheap), a filter cap at the input and another at the output, and maybe a small series resistor for safety. I mounted mine in a small plastic Radio Shack enclosure that included a board to mount the parts on. Drill holes in the box for the transformer wire and the output wires.
3. I added some wire to make positive and negative busses, then soldered a bunch of wires to each buss and the proper plugs (also available at RS) on the outputs. It's very important to wire the plugs properly, as polarity is not standardized. The pedals are labelled as to which part of the plug is positive and which is negative.
4. I mount the enclosure on the pedal board and, when I set up, move the transformer away from the board. So, all the pedals get clean 9 volts, and stray magnetic fields are far from the pedals.

Total parts cost is less than $10 (if you have a suitable wall wart around). I've got 6 pedals running happily. The only problem I had was when someone stepped on the transformer and broke the wire...

[eschertron]

I have a couple of 1-spots for my pedal board, not for fail safes but because I've run into the situation described here

It doesn't happen ALL the time, but many have noted that running two or more digital pedals off the same PS can result in a big increase in noise, if the power source does not feed those pedals in a manner that isolates them from each other. The problem is that digital pedals have multiple high-frequency clocks on them. On their own, they provide no audible noise, and no noise resulting from interaction with other analog pedals sharing the same power line. But if the clock signals riding on the power are free to move in both directions from digital pedal A to digital pedal B, they can interfere with each other to produce a great deal of audible noise.

which I discovered when I brought a 'Vox Time Machine' pedal into my lineup. it added an *incredible* amount of hiss to the audio path. Once I broke the power supply off (gave it a separate "isolated" supply) it behaved just fine. And 2x $20 is still way less than the cost of those brick units. There's a legacy supply on my Sans-Amp pedal, and the latest pedal came with an 18v wart, but all my power can sit nicely on a power strip and so keeps me happy by being out of the way.