smps, for pedal.

[km-r]

hey,

im finally done with the schematics for my "distortion-compilation pedal"... basically its a dist, od, insane-dist pedal...

and now i want to power it directly from the wall socket and decided to use smps since there is still space left in the case.

any of you who knows a good/simple smps schematic for low power applications? like 220v or 110v to 12vdc at 100mA... somewhat like that...

thanks!

[RaceDriver205]

Switchmode devices are a fair bit more difficult to make. Like, a LOT more.
I do believe that you can downconvert 240VAC straight to 12VDC with no transformer, but current is not very high (it probably doesn't need to be). I would recommend a bigger capacitor for C2.
Noise may be an issue, or it may not, I don't know.
http://www.zen22142.zen.co.uk/Circuits/Power/tps.htm

Of course, if your worried about getting zapped, or turning your metal cased pedal into a death-trap, buying a 'wall-wart' power supply is the way to go.

[R.G.]

Good reply, RaceDriver205.

An off-line power supply involves rectifying the AC power line, unisolated, as a first step. If you have not had direct, professional training on how to do this safely, your chances of getting hurt, even killed, are actually quite good. Even putting AC power wiring inside your box introduces a shock hazard. It is incredibly dangerous to try to use a non-isolated AC power supply in any audio equipment.

Not to mention the possibility of picking up hum and noise.

Get a wall wart.

[db]

Has anybody tried using N?kia or M?torola type mobile wall-warts?  I must have a dozen or more of these units knocking around the house and was thinking that they may be worth using for effects.  I did use a couple in parallel to replace a faulty unit for a set-top box.
Usually they're quite low voltage 5-6V but quite good supply capacity (>0.5A typically).  I haven't tried this but perhaps they can be wired head to tail for a bipolar supply with centre ground reference.

I don't know what the isolation is like in these units but they must be safe (CE marked etc.).  I suspect there's a tiny high frequency transformer to do the isolation.

I also don't know how noisy they are, not built for hi-fi of course, but maybe with a bit of filtering I would imagine they would be OK for most purposes (and cheap and readily available).

[R.G.]

Switch mode wall warts might work fine. They also might not. You gotta try them to see.

... ahem... there is one SMPS specifically designed and intended for effects. The 1Spot is under $25, at many dealers all over the world, and is not only designed for effects use, each one is individually tested on a high gain distortion pedal before it leaves the factory.

You might try one of those.