18v explained please.

[Loxton]

When can you use 18v on a pedal?
Do you require to check or install 18v/25v/35v or above electrolytic capacitors?
Also what difference does a charge pump affect when using 18v ? I'm guessing a charge pump converts 9v to 18v, but does that mean 18v converts higher?

Thanks in advance.

 

[twebb6778]

I'm not an expert by any means, but this is my understanding. Happy for people more knowledgeable to chime in.

You can supply a circuit with 18 V when the components allow for it.

Each component will have a maximum voltage that it can handle. Electrolytic capacitors generally have a much lower voltage tolerance than other components which is why you hear about them more when increasing voltage. For most components, maximum voltage is inherently associated with size, that is, the higher the maximum voltage, the larger the part will be. Because of this we tend to use the smallest voltages allowable to save space on the board.

This maximum voltage is generally twice the operating voltage of the circuit, so for a 9 V circuit you could probably get away with 16 V capacitors, but 25 V would be safer.

Same thing for a circuit which is operating at 18 V (regardless of whether it's receiving this from a charge pump or directly from the power supply), it's recommended to double the voltage to allow for spikes. You'd want to use capacitors rated to at least 35 V, but higher if space allows.

IC's, including voltage converters like LT1054 or MAX1044 that are typically used for charge pumps, also have a maximum voltage. The peripheral components will dictate how these IC's function, so it's not as simple as just doubling any supplied voltage. LT1054 for example has a maximum supply voltage of 18 V for example, so giving it 18 V will just fry the IC. If the function of the charge pump is converting 9 to 18 V, only supply it with 9 V.

Likewise, if you aren't confident that all the components in a circuit can safely operate at higher voltages, do not increase the voltage. It's very likely something will fail.

 

[Feral Feline]

Do NOT feed your charge-pumped pedal with a higher voltage than the circuit can handle.

...I'm guessing a charge pump converts 9v to 18v, but does that mean 18v converts higher?
...

Yes, if your pedal bumps 9v to 18v, then feed that pedal with 18v and it'll go to 36v... if all the components can handle it.
Depending on the pedal, its components and the manufacturer's configuration, a pedal may be okay fed with 12v (bumped by the charge pump to 24v), but feeding the same pedal with 18v (bumping to 36v) will fry the pedal — specifically whichever components can't handle that much voltage (op-amps, transistors, caps, whatever).


I like the higher headroom of 18v, gives some breathing space for my bass signal without compressing it or distorting it — unless it's a fuzz circuit, in which case 9v is fine. I still operate some ODs at 18v, The Elements for example, but I like my Barbershop at 9v. They behave differently at the different voltages, at least, that's my perception. My Cool Cat chorus sounds fantastic at 18v, but at 9v I can't even recall if it works at all!

Bass or guitar, if your pedal can safely operate at a higher voltage, try it, you might like it.

 

[Chuck D. Bones]

Or you might end up with a dead pedal. If the original manufacturer suggests running the pedal at higher voltage then it's ok. If you are willing to perform a parts stress analysis on the circuit, then you can figure out for yourself whether it's safe or not. It's not enough just to replace some capacitors, you have to evaluate every part. Most charge pumps will die above 12V.