When can a charge pump be used in a pedal?

[Dotted.eighth]

Hi guys,

I'm a new member here, but I've been roaming around the forums for a while. Hanging around the completed builds area in particular. Pretty inspiring yet demoralising at the same time, because it looks pretty complicated haha.

But enough waffle, onto my question- when can a charge pump be used in a pedal? I know that not every pedal can be powered over 9V, but some can. What are the rules? How do you know how high you can power it?

Thanks,
Joe

[shawnee]

Resistors and film caps are not a factor but you will need to make sure that your electrolytic caps are rated above whatever voltage you are going to push through them with a little breathing room (maybe use a 25v cap for 18v supply). Transistors are usually pretty safe but spec sheets on sites like MOUSER ELECTRONICS will tell you the limits of that particular device (specs can vary slightly from brand to brand so try to pull up the exact device if possible). The biggest component danger is the IC chips. Check those against a spec sheet for sure. The charge pump IC itself also needs to be checked to see if it can provide enough current to power the pedal. The LT1054 can provide way more current than a TC1044 type chip and should be used for high current pedals like delays or if you need to put more than 12v on the input of the charge pump (which usually doubles the voltage on the output). The average dirt box doesn't draw much current so the TC1044's work well for that. If you have a particular pedal in mind, please ask questions.

[jkokura]

It's sort of interesting what can and cannot be powered at 18V. In theory, anything can as long as the components can handle it. Datasheets will tell you what can handle it and what can't.

But further to the discussion, not everything actually benefits from it. In some cases, running at 18V actually detracts from the effect. For example, some people think running overdrives at 18V is automatically awesome, but in some cases I've preferred the sound at 9V. Some are better at 18V thought.

The most common use for a road rage board is in fuzz pedals that require -9V instead of +9V, so the charge pump is used to invert the power. Second most common use is to ramp up the voltage for pedals using BBD circuits like choruses and delays which like to be run at 15V.

Jacob