freestompboxes.org

This is the right way to do it:
This is commonly done for a few reasons: bipolar electrolytic capacitors are (usually) of poorer quality than polarised ones, manufacturers and suppliers often don't have stock of these bipolar capacitors, and it's usually trivial to make one side of a capacitor "more positive" than the other, thereby biasing a normal electrolytic capacitor.

It must be considered that electrolytic capacitors are inherently noisier than other types, and can suffer from microphony. In many instances, "designers" just throw in an electrolytic capacitor without considering its actual reactance and the practical frequency response of the circuit they're putting together. I've often seen guitar effects boxes with responses down to the milliHertz region! Good designers know that there's not much point in having a response much below the frequency of the lowest string on a guitar (or a bass), and that a response down to very low frequencies is often detrimental - the "handling noise" from a guitar or a bass can really cause the speaker cones to flap if very low frequencies are allowed through!

I remember one well-known (and respected) maker of a triggered filter who had huge problems with the filter spontaneously changing frequency in response to inputs that he couldn't hear. When I pointed out that the over-specified input capacitor to the sidechain circuit gave the rectifier a response down to <2Hz, the value was changed to 1/20th of its original value, and the problem disappeared!

Exercises for beginners: Look up "Capacitive Reactance" and see how it changes with frequency. Look up C-R filters and find out how to calculate their response. Try designing some simple C-R filters of your own and try putting them in the output of a simple booster or fuzz circuit, and listen to the change you can make with just a couple of parts!

287m wrote:normally, you right.
normal elco actually conduct in the reverse direction, two 1uF polarized act like they each have a diode in parallel with them that conducts when the voltage is backwards for that one cap.

grrrunge wrote:Where did you learn that? I have never seen any diodes in the equivalent diagram for electrolytics. Only capacitance, inductance and resistances.
As far as i know, the only reason electrolytics are polarised devices, is because improper DC-bias will break down the dielectric layer.

The diode thing isn't perfectly accurate, but the rough idea is correct. Reverse-biased electros conduct DC, but correctly biased electros don't. When you put two equal value electros back-to-back in opposite directions, each electro blocks DC in one direction, so you end up with a non-polar cap of half the given value. That part is fine.

I don't understand the claim that series 1uf electros don't follow the formula for adding caps in series, though. No idea where that came from.

induction wrote:

287m wrote:normally, you right.
normal elco actually conduct in the reverse direction, two 1uF polarized act like they each have a diode in parallel with them that conducts when the voltage is backwards for that one cap.

grrrunge wrote:Where did you learn that? I have never seen any diodes in the equivalent diagram for electrolytics. Only capacitance, inductance and resistances.
As far as i know, the only reason electrolytics are polarised devices, is because improper DC-bias will break down the dielectric layer.

The diode thing isn't perfectly accurate, but the rough idea is correct. Reverse-biased electros conduct DC, but correctly biased electros don't. When you put two equal value electros back-to-back in opposite directions, each electro blocks DC in one direction, so you end up with a non-polar cap of half the given value. That part is fine.

I don't understand the claim that series 1uf electros don't follow the formula for adding caps in series, though. No idea where that came from.

oh crap, just show this now

im not alone

B_Y_O_Bass wrote: when you need a non polarized capacitor and you have none, wire up the negatives of two half value capacitors together, et voila, a non polarized cap is made.

maybe me and B_Y_O_Bass in the wrong side of heaven
and maybe(again), its suggested from https://www.diystompboxes.com/wiki/inde ... CAPACITORS
and sorry for bring you guys to this mistake.

hey, i not have component tester now. if you have, please show to me and B_Y_O_Bass, so we can move to right side of heaven

thanks for Blitz Krieg for remembering this thread from vibro thread

287m wrote: its suggested from https://www.diystompboxes.com/wiki/inde ... CAPACITORS

Well that is quoted from R.G. Keen who is considered an authority. If he sees this I'm sure he will chime in.

When in doubt, trust RG over me. I always do.

I guess it does make sense. Two electros in series don't behave like normal caps in series because when they are reverse biased, they act like jumpers. So for any given signal polarization, only one of the caps has a voltage across it, the other one just sort of disappears (ie acts like a short). At least that's how I read it.

The 'diodes in parallel' thing is slightly misleading unless the diode has a tiny Vf (corresponding to the 'tiny region near zero volts where they withstand a tiny reverse voltage' and then the normal series cap math still applies). But that's a nitpick.

Thanks for clearing that up for me. I stand corrected.

induction wrote:When in doubt, trust RG over me. I always do.

I guess it does make sense. Two electros in series don't behave like normal caps in series because when they are reverse biased, they act like jumpers. So for any given signal polarization, only one of the caps has a voltage across it, the other one just sort of disappears (ie acts like a short). At least that's how I read it.

The 'diodes in parallel' thing is slightly misleading unless the diode has a tiny Vf (corresponding to the 'tiny region near zero volts where they withstand a tiny reverse voltage' and then the normal series cap math still applies). But that's a nitpick.

Thanks for clearing that up for me. I stand corrected.

Induction, i just honest especially for you
i just make that (the 1u back to back elco caps) once, when build my first clone some year ago.
yes, your first thought is right, a ts clone.
then, when i have non polar, i change the back to back with real non polar
amazingly, sound still same. not drastically change like when change 820n to 47n, for example
i just dont know how that thing happen. i just suggested first from tv tech, we meet when i go to local store to buy 1u NP, but the stock is empty
the tv tech just said
'hey don't worry. you buy two 1u elco and solder like this (he show the back to back config)
then the outer is solder to your pcb'
that is my first and only i build the back to back caps in pedal fx
its my story

someday, i found https://www.diystompboxes.com/smfforum/ ... ic=53737.0
and i just