18v charge pump or 18v source

[CthulhuOO7]

Wasn't sure where this should go, possibly beginner stuff.
I'm working on the original CB Galileo:

(http://tagboardeffects.blogspot.com/2012/10/catalinbread-galileo.html)

Everyone says an 18v charge pump works well with this one. I've not done a charge pump before, but understand it boosts the 9v to 18v? If I have an 18v power source, I won't need a charge pump? Just make sure all components are rated higher than 18v?

Thanks much!
Jeff

[balazs.bencs]

You are correct.

The charge pump makes 18V from a 9V power supply. If you have the 18V option on your power supply, then you can use that, all you need is the pedal built as it is, with caps rated at least 25V. (make sure you have always some room for tolerances)

[GrooveChampion]

Speaking of pedals that are built for 18V, I've built a Klon(true bypass version) and the two 47uF electrolytic caps, the only ones I could find were 16V. Now I connected it, it fired up and works, are these two caps actually receiving 18 volts?

[balazs.bencs]

Well, I'm not entirely sure, but there's the risk - those caps can blow up, and that is not a pleasant thing when you are around.

[GrooveChampion]

Well, except for these two 47uF caps, the rest are rated higher. According to the 7660 pinout one is getting 9V and the other -9V

Wait, is pin 8 of the 7660 responsible for outputting 18V?

[rocket88]

hold the phone, this is something much easier they it's being made out. first, every component needs to be rated then whatever voltage you're planning on running it, ie if you're running a pedal at +9V 16V rated caps are fine, if you're running a pedal at +18V you want a minimum of 24V caps, etc. if the voltage of the caps are lower then the voltage then they will explode, and i do mean explode, it's just a matter of when. you always want the caps to be rated higher, and not just by 1V or 2V to allow room for error in voltage since you may not get exactly the voltage planned.

the easiest way to handle the situation is to always use high voltage caps. for me none of my caps are rated below 50V, so i never have to think "is this cap rated high enough?" the trade off is the size of the cap, and want to get the smallest cap with the highest voltage.

groove, as for the klon layout, pin 8 of the 7660s is +9V input. so you don't need a higher rated cap, but like i said, i remove all risk by using high rated caps.

[GrooveChampion]

I'd remove all the risk I can, but desperate times....

[Sensei Tim]

What rocket88 said.

In most pedals that have integrated charge pumps you don't need 25V+ caps on the input power filtering side (components between the 9V input and the charge pump).  

This helps if you have a tight space and the 100/220/470 uF filter caps.

That being said, i hate having 3 or 4 different voltage electrolytic caps in my parts drawer.

1st world problems :)

[rocket88]

groove i hear ya. over time i've weeded out, used, or gotten rid of my lower voltage electrolytics. not to mention i only use panasonic evq caps which are rated at 63V, plus they're nice and small. as far as keeping size down of electrolyics, i use the smallest caps i can with the highest voltage. in some cases i'll use a narrower electrolytic that's taller to squeeze into tight space.

it happens over time, and something i picked up through experience. i can't tell you how many caps i have sitting in containers that are lower voltage that i don't use anymore, but if i really needed them i'ld use them.