18v for FL301 from Pedal Power 2

[jkokura]

So I have a Pedal power 2, (http://www.voodoolab.com/pedalpower_2.htm) and I need to get 18v to my FL301 from Tonepad that I'm going to build.

There's two ways I can go about this: 1. I use or make a special cable combining two 9v outputs to give me 18v. I'm not sure if 2 9V is series or parralel will give me 18v, so if someone can tell me that I'll make my own cable, and if not, then I guess I have to spend 10 bucks to get that special cable they make. 2. I use a charge pump which takes 9v in and gives me 18v out. The FL301 will be in the same box as a phase 45 and an EA Trem, so if I do that I don't know if I can run all three of them off of one DC Jack or if I have to have a a separate 9v jack for the FL301. I know that you can run multiple PCB's off one source (Parallel or series?) as long as they don't use up more mA than your supply gives.

Any advice is appreciated. I don't really know how a charge pump works, and I'm trying to learn about my parallel and series power questions, but my googling skills are turning up short.

Jacob

[G. Hoffman]

They need to be in series.

Here is a good way to remember it.  Voltage is a difference between two points in a signal.  So, if you measure across the terminals of a battery (or whatever), you are measuring the difference between those two points.  In parallel, you connect the ground to the ground, and the hot to the hot, so they are the same voltage.  If, however, you run them in series, you have the 9V difference across one battery, and then another 9V difference across the other, and they add.

At any rate, you need series.


And if the output has enough current, you can run them all off of one supply, but will need to drop the voltage down to 9V, either with a voltage divider or a regulator of some sort.  

Another option would be to run two 9 volt supplies to the box, and run the two 9V effects off of one supply, and run the other off both.  Just connect the negative side (the black wire of a battery snap) of the second supply to the hot side of the other supply.  Ground is the negative terminal of the "first" supply.  The 9V effects take their power from the junction of the two power supplies, and the 18V takes from the hot side of the "second" supply.  

I'm not explaining that well.  Like this:



Basically, it is exactly like making a series cable - you're just doing it in the box.  I'm not 100% sure it wouldn't cause some noise problems, but I'm pretty sure it wouldn't.  Certainly, it couldn't hurt to try it.


Gabriel

[jkokura]

I think that's a good explanation Gabe, and then it wouldn't matter if I used the 18v cable 'accidentally' into the 9v one and blew something.

Another thing I just realized is, what about the components on the FL301 - don't they all have to be rated for higher than 18v? I mainly use 16v electrolytic caps...

*Edit* Upon a closer look at the layout, it appears that the 18v gets brought down right away to 12v via a regulator! There's only a diode a 10uF cap attached to the 18v source before going to ground. IC 6 is a 12v regulator that then supplies power for the rest of the board.

So now the question is - Why don't I just use 12v, which the PP2 gives me already!

Jacob

[G. Hoffman]

Another thing I just realized is, what about the components on the FL301 - don't they all have to be rated for higher than 18v? I mainly use 16v electrolytic caps...

Yup.



Gabriel

[jkokura]

I edited my response Gabe - maybe you could explain it to me better if you had a look at the layout from tonepad.

http://www.tonepad.com/getFileInfo.asp?id=49

Jacob

[G. Hoffman]

So now the question is - Why don't I just use 12v, which the PP2 gives me already!

No good reason.  The regulators in the PP2 are pretty darn good - they are LM317s, by the way; I had mine open the other day - so they are probably doing at least as good a job as what is in the circuit.  It would mean you would probably have to add a 9V regulator for your other pedals, but then you only have one power cable running to the box. 

Or you could redesign the other boxes to run at 12V.  It would give you a bit more headroom, which doesn't seem a bad idea with those particular circuits, and it could sound pretty cool.  Or not, of course.  It looks like the only IC you've got is a TL072, which can handle a 36V PS (±18V, actually) so a 12V supply shouldn't matter to it.  You'd probably have to change the 4.7V zener on the Phase 45, though, and a bunch of resistor values.  Kind of a pain, but then it could also be a good learning experience, right?  I'd probably go that route, but then I'm a bit of a masochist too.

Then again, I use 35V and 50V caps all the time anyway, just for the sake of over-designing things. 


Gabriel

[jkokura]

I think what I meant was to have two jacks - one for 9V for the Trem and Phase, and the Flanger would get a 12v jack. The trouble is understanding if the FL301 will work fine on 12v or if it actually 'needs' 18v that gets regulated down to 12v. It's much easier to give it 12v to start with, case I don't need any fancy wiring - just a flick of the switch on my PP2.

Jacob