Q about capacitors

[nelson476]

on a capacitors  it shows the ohms value and the voltage, if it doesn't specify the voltage of the capacitor in the schematic i just need to use one that is more then the input voltage?? like if its a .47uf cap and the the whole thing is powered by 9volts then i can use any .47uf cap as long as the voltage is greater then 9volts ?? 
any help would be great
thanks
_Nelson476_

[Seljer]

M = mega = 10^6 = million

2M2 = 2.2M (it saves you the nuisance of writing that dot) = 2.2 million ohms = 2200000 ohms

[nelson476]

thanks selier...    i just changed my post topic so i wouldent be making a bunch of threads. i hope thats ok.

_Nelson476_

[gaussmarkov]

on a capacitors  it shows the ohms value and the voltage, if it doesn't specify the voltage of the capacitor in the schematic i just need to use one that is more then the input voltage?? like if its a .47uf cap and the the whole thing is powered by 9volts then i can use any .47uf cap as long as the voltage is greater then 9volts ?? 
any help would be great
thanks
_Nelson476_

correct.  like use a 16v. 

smaller voltages come in smaller packages.  so that's why you might go 16v instead of 25v.  otherwise, you could use a 500v cap AFAIK.

[nelson476]

thanks!   ok.. yet another Q.  i have a schmatic and it calls for a 20uf polarized cap and i cant find a 20uf cap.. is there such thing?
thanks
_Nelson476_

[gaussmarkov]

thanks!   ok.. yet another Q.  i have a schmatic and it calls for a 20uf polarized cap and i cant find a 20uf cap.. is there such thing?
thanks
_Nelson476_

yes, 20uF should be out there somewhere, but you can use a 22uF in most cases without it making an appreciable difference.  how are you using that cap?

[phaeton]

Capacitors are actually valued in divisions of a farad, not ohms, but you've got the right idea.  It's always ok to use a capacitor of the same value but with a higher voltage rating, and it will rarely have any effect on anything except the layout of your circuit (because the capacitor might be physically larger).

You can also usually exchange types (ceramic, poly, metal, electrolytic) just so long as you observe the correct polarity or non polarity.  Some folks will say it will change the tone a little bit (depending on where they are in the circuit).  You can also substitute caps of close but different value.  Depending on where the capacitor is used, it might affect the frequency response of the circuit, but it should always work.  So if you have a circuit that needs a .1uF but all you have are .082uF or .15uF go ahead and use one.  You can always change it later if you want

There are a few exceptions to this, but you'll probably not run into those scenarios when building 9V stompboxes.

[nelson476]

hmm. what do you mean by "how am i using it" ?? 
(edit) (woops lol i didn't even notice i valued a cap with ohms lol    )
thanks
_Nelson476_


if this helps with my Qs this is what im gointo to attempt to make. 

http://www.diyguitarist.com/PDF_Files/EA-TremoloPCB.pdf

[nelson476]

im assumeing that if it says to use a 25k potenitiometer its ok to use a 20k??
and how to i know whether to use linear or logarithmic??  or dual linear or dual logarithmic.
i remember reading about this i think but i  cant remember where it was..
thanks again
_Nelson476_

[QSQCaito]

on a capacitors  it shows the ohms value and the voltage, if it doesn't specify the voltage of the capacitor in the schematic i just need to use one that is more then the input voltage?? like if its a .47uf cap and the the whole thing is powered by 9volts then i can use any .47uf cap as long as the voltage is greater then 9volts ?? 
any help would be great
thanks
_Nelson476_

correct.  like use a 16v. 

smaller voltages come in smaller packages.  so that's why you might go 16v instead of 25v.  otherwise, you could use a 500v cap AFAIK.

I read somewhere the higher the voltage the better.. maybe its a very tiny differencet that doesn't woth changing a whole pcb for such a tiny difference.. and spending the money

bye bye

dac

[Paul Marossy]

I read somewhere the higher the voltage the better

This is true in the case of ceramic caps. The low voltage ones (100V or less) are far less linear than the 1kV or higher ones. In terms of the voltage rating, most other types of caps don't matter much in a stompbox, other than the voltage rating. As a general rule, use 16V minimum.

[brett]

Hi
About the linearity of high voltage ceramics - that's a new one to me.  Probably would be to most others here, too.

But in general, I totally avoid ceramics.  MKT are my capacitor of choice.  Slightly more expensive than greencaps and ceramics (maybe $1 per build), but they are more compact and have a standard lead spacing (5 mm).  They are mostly rated at 100V, but I once accidentally used one at 400V (for 6 months) and didn't destroy it.  Up to a point, they self-heal.

Concerning electro cap voltage ratings.  Why bother buying 10V or 16V caps?  25V and 33V caps cost maybe 5c more. 

Work that extra one hour of overtime and earn enough for high-quality caps in 20 boxes! 
Or build 19 quality boxes instead of 20 less good ones.
cheers

[Fret Wire]

I like the Panasonic ECQ-V's, nice and small. I was also lucky and found a good sized batch of 2.2uf 50v film caps that are only slightly bigger than a 1uf Panasonic. Great for fuzz input caps. Brett's right about electro's: use at least 25v, and you won't have to worry if you do a 18v build.

In the end, as long as you observe proper voltages and polarity, anything will work. We all have our preferences. Whether it matters or not, I use metal film resistors and film caps. I also use tants alot, 4.7uf up to 47uf. I like having a build without any electros. Nothing will ever dry up. Same with some of us that always arrange our resistors so all the tolorance bands point the same way. No sonic value, we just like it. My money, my time, and my satisfaction.

[Paul Marossy]

About the linearity of high voltage ceramics - that's a new one to me.  Probably would be to most others here, too.

Read this: http://members.aol.com/sbench102/caps.html
My own ears also bear witness to his findings. 

[Fret Wire]

About the linearity of high voltage ceramics - that's a new one to me.  Probably would be to most others here, too.

Read this: http://members.aol.com/sbench102/caps.html
My own ears also bear witness to his findings. 

In what regard? Hv ceramics vs lv ceramics? In what ckts? And in what places in those ckts? I take it you're not talking about 9v stomps. In amps, I generally replace ceramics with silver micas, or where I prefer ceramics, I usually just go to hv types. Mica isn't always desireable. I curious which ckt and where you A/B'd the hv/lv ceramics.

[brett]

Hi
Fortunately, most the impedance of audio lines means that most caps are mid-sized.  Only occsionally are large caps used in the signal path (e.g. 2.2uF into the low Z - 20kohms - Fuzzface).  Therefore, greencaps and MKTs can be widely used.  Mostly, small ceramics (10pF to 100pF) are used to bypass high frequencies to ground, to V+, or across the feedback loop of op-amps.  In those situations, it doesn't matter that they're not so good.
cheers

[Paul Marossy]

im assumeing that if it says to use a 25k potenitiometer its ok to use a 20k??
and how to i know whether to use linear or logarithmic??

The general rule that I use is log always for volume controls, sometimes gain controls, and linear for everything else works OK. Some circuits use log pots in tone circuits or gain controls and some circuits also use reverse log pots. The reverse log pot is the one that is most difficult to try and substitute.

In this case on the EA tremolo, the 20K pot would work fine.

In what regard? Hv ceramics vs lv ceramics? In what ckts? And in what places in those ckts? I take it you're not talking about 9v stomps.

Signal path. Even at 9V, the low voltage ceramics don't sound very good to my ears.

Mostly, small ceramics (10pF to 100pF) are used to bypass high frequencies to ground, to V+, or across the feedback loop of op-amps.  In those situations, it doesn't matter that they're not so good.

Yeah, for the most part, I agree with that.

[gaussmarkov]

hmm. what do you mean by "how am i using it" ?? 
(edit) (woops lol i didn't even notice i valued a cap with ohms lol    )
thanks
_Nelson476_

if this helps with my Qs this is what im gointo to attempt to make. 

http://www.diyguitarist.com/PDF_Files/EA-TremoloPCB.pdf

well, here's some general info that's relevant.  electrolytic capacitors come in fairly wide tolerances, at
least compared to resistors.  a common choice is the xicon aluminum electros that are plus/minus 20%.
so a 20uF cap could easily be an 18uF or a 22uF cap.  good circuit designers take this into account and
their circuits do not depend critically on a specific value when such variation appears in the supply used
for production.

[Paul Marossy]

well, here's some general info that's relevant.  electrolytic capacitors come in fairly wide tolerances, at least compared to resistors.  a common choice is the xicon aluminum electros that are plus/minus 20%. so a 20uF cap could easily be an 18uF or a 22uF cap.  good circuit designers take this into account and their circuits do not depend critically on a specific value when such variation appears in the supply used for production.

Yep, that's true. If you want something with closer tolerances and better performance, use tantalum caps.