Clean power from any source? (Battery, unreg., reg. power supplies)

[R.G.]

I probably should have mentioned this somewhere.

There is no difficulty at all in getting one pedal to work from any power supply, even one which is the wrong polarity, AC, or which varies from above 9V to below 9V. There are power supply alphabet-blocks to handle all of those.

What's hard is getting a second through fifty-third pedal to use the same power supply and simultaneously to connect to the first through signal ground. It's the old positive-ground/negative-ground problem on steroids.

I have several times come up with a small isolated power supply which produces isolated 9V for just this purpose. I've just not hit the right combination of easy enough for the beginners that will flood the forum with "...butbutbutbut my isolated power supply doesn't work" and affordable.

Here's one. Bring in your whatever power from a jack which does not touch the chassis (hence grounding one side). Feed it through a full wave bridge, then a BFC, and have that feed a chopper of some sort, perhaps at high audio. A 555 will do for low powers, a CMOS oscillator driving BS170s will do for a few watts. Feed the chopped DC into a Xicon 400mW audio transformer. Take the output of the Xicon, rectify and filter it, then feed it to a 7809. This isolated secondary can then be connected to any ground you like.

It suffers from the same ills as any switching transformer: it uses power magnetics to make interference and be expensive, it radiates interference, and you have to work hard to keep interference out of your target circuit.  But it works.

[birt]

i actually understood everything said in your post

and now i really wanna know what's inside those aphex pedals :p

[Cliff Schecht]

A SMPS is the way to go when you want "universal" input power and nicely regulated output. With a proper design, it would be possible to derive a +-9 V rail as well as an 18 V rail and whatever other 9 V based rail you're interested in. This would be pretty easy to implement with a flyback design, you just custom wind your coupled inductor for whatever rails you need. These can be very quiet if filtered properly and provide well regulated power. Adjusting the output (i.e. implementing a "sag" control) is easy as well. So many possibilities!

The OneSpot is a good standard 9 V switcher if you don't feel like making one .

[earthtonesaudio]

Here's what I think I'll end up using, as the basis of the system:
http://www.national.com/mpf/LM/LM2936.html

It's nearly perfect: reverse protection, wide input range, low current draw, small footprint (TO-92), few parts, not too expensive ($2.65 at Digikey)...
The only other requirement is the high voltage for the effect circuit, and for that I'm pretty sure I'll be using a CMOS-based %^&*roft-Walton.
For my requirements, I'm estimating I can get away with 2 ICs and a dozen or so passive components.  Not bad.

[earthtonesaudio]

Now what kind of multiplier should I use...?  I'm thinking either the parallel-capacitor type, or parallel-in/series-out type.
Parallel/series shown in figure 2 here:
http://dustbunny.physics.indiana.edu/~paul/cwbase/

"Standard" all-series, as well as all-parallel are shown here:
http://www.techlib.com/files/voltmult.pdf

[earthtonesaudio]

A bit of an update:

I crammed the circuit I want to power over to one side of the breadboard to make room for the voltage multiplier.  I started with a 555 making a 50% duty cycle square wave, feeding a single-stage multiplier using 1uF aluminum electrolytics as the capacitors, and a mix of Ge and Schottky diodes.  I got about 11V (under load) from a 9V input.  Wretched.

Then I changed the caps to 10uF aluminum electrolytics.  This time I got about 14V, no other changes.  Then I added a second multiplier stage but the voltage only increased to about 16V.

Tonight I'm planning on swapping the electrolytics out for some 1uF multilayer ceramics, and I'll probably swap the diodes for normal 400x series.  I'm expecting big improvements!