Regulators ONLY to feed multiple voltages?

[Kindly Killer]

I need to put together a pedalboard fast for a show on Friday (backing an artist who is passing thru). I have a tc nova drive (12v), a zoom g2 (9v), a boss rc-2(9v) and a bunch of footswitches (the switches with LED's are fed by 9v).

I want to just run one cable for DC so I found an old PSU from a Mackie firewire audio interface, which I assume is decent because it was a clean sounding interface. It is rated 12v and is good for 1 amp of juice. It reads 15v with no load.

Questions: do I need anything else in my box other than what is pictured? I notice in most schematics with regulators there are electrolyics before and after the regulators. What are those for and how do you chose values? If I may assume that my wall wart has some filtering [how would I know for sure?] do I need anything other than the regulators in my breakout box? Does having each type of thing (digital effects, boss looper, bypass boxes + amp switcher) on its own regulator address the ground hum problem R.G. Keen talks about in this: http://www.geofex.com/Article_Folders/Spyder/spyder.htm  Or does that only work if they are actually fed by separate coils?

[Processaurus]

I want to just run one cable for DC so I found an old PSU from a Mackie firewire audio interface, which I assume is decent because it was a clean sounding interface. It is rated 12v and is good for 1 amp of juice. It reads 15v with no load.

Actually it is probably noisy on its own, because it is unregulated, like most non pedal specific wallwarts.  The firewire thing surely has internal regulation. 

Questions: do I need anything else in my box other than what is pictured?

Yes, capacitors.

I notice in most schematics with regulators there are electrolyics before and after the regulators. What are those for and how do you chose values?

They are there for stability of the regulator.  They are necessary.  Also a film or ceramic cap in parallel is good, because electrolytics don't stabilize at high high frequencies.  The regulator can oscillate at radio frequencies without them.  You chose the value by looking at the example circuit in the datasheet.

If I may assume that my wall wart has some filtering [how would I know for sure?] do I need anything other than the regulators in my breakout box?

It would be safe to assume there is some filtering in the wallwart (otherwise it wouldn't be DC).  The regulators will work fine as long as their input is always a couple volts above the output, otherwise they will "drop out", meaning the regulation will fail momentarily.

Does having each type of thing (digital effects, boss looper, bypass boxes + amp switcher) on its own regulator address the ground hum problem R.G. Keen talks about in this: http://www.geofex.com/Article_Folders/Spyder/spyder.htm

They do nothing for that problem.  The grounds in your circuit are all physically connected.  That may or may not cause noise problems.  If there is noise, I would just go with a different PSU for the digital pedals.

Or does that only work if they are actually fed by separate coils?

That is the bulletproof solution for power supply noise on the ground.  That's what the voodoo labs pedal power II does.

Nothing is really gained by having multiple 9v regulators.  I would just do one 12v regulator and one 9v regulator.  You may want a different wallwart than the 12v mackie one, because it needs to always be a few volts over the output of the 12v regulator.

Hope that helps!

[PRR]

> put together a pedalboard fast for a show on Friday

IMHO: bad idea. Putting critical systems together on short deadline is asking for trouble, on-stage with an angry Famous Artist.

However.....

> I notice in most schematics with regulators there are electrolyics ... how do you chose values?

Steal values from the schematics. (Only call it "research.")

Assuming the schematic is for a "similar size" application, not a small clock or a large power amp.

"Probably" the guy who did the schematic knew something about the craft; at least something more than you do today.

What Ben said too. This won't break ground loops; you should test all the pedals together a week or two ahead of show so that you have time to work out problems or order multiple windings/warts for separate power. Without multi-windings/warts, there's little reason to have multiple regulators: one big 9V (and one 12V if needed) will work. (The power company gives you one 120V pole-transformer, not a separate 120V transformer for every light, TV, and Fender you plug in; a good power source can feed multiple loads.)

[Kindly Killer]

IMHO: bad idea. Putting critical systems together on short deadline is asking for trouble, on-stage with an angry Famous Artist.

Yeah it's pretty far from ideal, but I had to add the looper to the 'board and my usual, tiny, minimal board just wont' accommodate it. Also I have a show tonite and Wednesday, plus rehearsals, so hopefully that is enough time to iron out the kinks.

How's this look? I'm breadboarding it now BTW

[Kindly Killer]

PS I found a 18v, 850mA wall wart that I'm going to try.

[Kindly Killer]

K it was noisy and that was all the time I had to monkey with it. Oh well - it was a bad idea. I'm going to just get through the week and run two DC cables out to my pedalboard - no biggie. I just did a google search for "nova drive psu" and apparently it is a demanding pedal, power wise, so maybe i'll save my power tinkering for an easier pedal board.