Capacitor Voltage Ratings

IvIark · Post by **IvIark** » 20 Feb 2010, 02:13

I've heard people say that higher voltage electrolytic caps can sound better but in all honesty I've never noticed any real difference. I'd always choose the highest rated cap that can comfortably fit on the board, which will give you some freedom with other (maybe higher voltage) builds and give you less of a concern about spikes. But if I only had a 16V cap for a 9V pedal, I wouldn't be too concerned.

I do like higher voltage ceramics though, better quality and closer tolerances (at least in the ones I used).

white_cat_7000 · Post by **white_cat_7000** » 27 Feb 2011, 00:35

IvIark wrote:I've heard people say that higher voltage electrolytic caps can sound better but in all honesty I've never noticed any real difference. I'd always choose the highest rated cap that can comfortably fit on the board, which will give you some freedom with other (maybe higher voltage) builds and give you less of a concern about spikes. But if I only had a 16V cap for a 9V pedal, I wouldn't be too concerned.

I do like higher voltage ceramics though, better quality and closer tolerances (at least in the ones I used).

Aside from them being akwardly large, is 100v or 200v ok if i want to experiment? I can find Ceramic caps with the proper values but i want to know if using a 200 volt will do no harm if i can manage to get it onto the board. Thanks!

Hides-His-Eyes · Post by **Hides-His-Eyes** » 27 Feb 2011, 10:41

None whatsoever. But a 200V electrolytic where the schematic calls for a 47u cap will be enormous.

DrNomis · Post by **DrNomis** » 04 Mar 2011, 16:14

I seem to remember using 3000V ceramic caps in a circuit running at 9V once, it worked fine, and no damage whatsoever was done to the rest of the circuit......

Provided that the voltage rating of a cap is equal, or greater than the supply voltage, it shouldn't be a problem, personally I will err on the side of "greater than", when selecting components for a circuit build....

scream314 · Post by **scream314** » 04 Sep 2011, 10:27

I tend to use 16V or greater elcos. It is safer this way, they don't die even if you plug a 12V PSU in, and they are not too big. But in general you should pick a voltage rating equal or greater than the power supply voltge, that your circuit will ever see.

asatbluesboy · Post by **asatbluesboy** » 07 Sep 2011, 15:05

I'm paranoid, so I just assume I'll run my effects at 18V tops and get capacitors rated for at least twice that--in case there's some spiking or whatever...

DrNomis · Post by **DrNomis** » 07 Sep 2011, 15:22

asatbluesboy wrote:I'm paranoid, so I just assume I'll run my effects at 18V tops and get capacitors rated for at least twice that--in case there's some spiking or whatever...

Anything from 25 to 50V rating for caps is fine for operation in a circuit supplied with 18V....

Incidentally, when you rectify the AC voltage from an 18V plugpack, the filter caps will charge-up to the Peak voltage, the voltage rating of AC plugpacks is quoted in Volts RMS, the RMS voltage is about .707 of the peak voltage so, the Peak voltage will be greater than the RMS Voltage, to calculate the Peak voltage the formula is Vrms/.707, in this case 18.00V/.707= 25.459689V Peak....

KHELSTROM · Post by **KHELSTROM** » 07 Sep 2011, 17:14

I met Alfonzo Hermida back in 2009 at the New York Amp Show and we talked tech for a while. One thing we touched on was actually just this topic. In reference to the zendrive he stressed that a key component to the feel of that pedal is due to the capacitors used in the power supply. Specifically he said that they must be low ESR and that the rated voltage should be as close to the intended working voltage as possible. In the case of the zendrive the intended working voltage would be 9V and I believe he said he uses caps rated at 10V or 12V.
This makes sense of the way he responded to this question on the FAQ page of his website:

Q: Can your pedals run at 18V?

A: No. They were designed to run efficiently at 9V. Some people have used them at 12V but don’t report any significant benefits.

The way he explained it to me was that by the caps being both low ESR and being operated close to their rated voltages they are able to discharge more quickly when current is drawn by an incoming signal.

DrNomis · Post by **DrNomis** » 07 Sep 2011, 20:22

ESR is short for Effective Series Resistance, you could think of it as an imaginary fixed resistor that is connected in series with the capacitor, inside the capacitor is a rolled-up sandwich of two long strips of Aluminium foil separated by a porous membrane which is impregnated with an electrolytic paste, this paste forms an oxide layer on one of the strips of Aluminium foil and this happens when the capacitor is "formed" by connecting it up to a DC source, manufacturers try to get a capacitor's ESR as low as possible so that the voltage drop across it is as small as possible, having a very low ESR means that the capacitor will be more effective at shunting AC to ground when used as a filter capacitor in DC supplies, it is also a necessity in Switch-mode Power Supplies too....

KHELSTROM · Post by **KHELSTROM** » 09 Sep 2011, 02:42

DrNomis wrote:ESR is short for Effective Series Resistance, you could think of it as an imaginary fixed resistor that is connected in series with the capacitor, inside the capacitor is a rolled-up sandwich of two long strips of Aluminium foil separated by a porous membrane which is impregnated with an electrolytic paste, this paste forms an oxide layer on one of the strips of Aluminium foil and this happens when the capacitor is "formed" by connecting it up to a DC source, manufacturers try to get a capacitor's ESR as low as possible so that the voltage drop across it is as small as possible, having a very low ESR means that the capacitor will be more effective at shunting AC to ground when used as a filter capacitor in DC supplies, it is also a necessity in Switch-mode Power Supplies too....

I know all about ESR and cap construction but what conclusion are you drawing in regard to this property and how it relates to the characteristic of an overdrive?