Cap Q's

[gotdabluz]

I am getting ready to perf up a Jack Orman "Son of Screamer" with a few mods.  One of the things I am going to do is use a TI TLE2426 virtual ground for rail splitting.  I will probably use RG's mosfet power protection scheme as well.  I am no guru, but I really want to understand what it is that each component does.

Looking at various schems I am sure that I will need a cap across the battery connections, between the mosfet and rail splitter, but I can't say I really understand why.  So my questions are:

1) What purpose does this cap of larger uf value serve?

2) How does one determine the proper value?  I have seen lots of different designs with various values from 10-220uf.  How does one make this determination?

I'd like to avoid using aluminum caps if possible . . . especially in the audio signal path.  

3) Can the output cap which is a polarized 1uf (aluminum?) be substituted with something like a NP metal film cap?

Thanks ahead for helping to enlighten a noob.

[gotdabluz]

Ok . . . after pouring over various schem annotations (fx and non-fx), I guess that I have found out a little bit more here.

From what I understand, the large cap across the power rails acts as a power reservoir, keeping the available current for the circuit at a happy level . . . however . . . I still don't understand how one determines just how big a cap is needed.  The Son of Screamer uses a 47uf cap, but I have seen caps as big as 220uf on other designs.

Also . . . the SOS has a polarized 1uf cap on the output of the effect . . . can a non-polarized cap be used in it's place?

[petemoore]

Ok . . . after pouring over various schem annotations (fx and non-fx), I guess that I have found out a little bit more here.

From what I understand, the large cap across the power rails acts as a power reservoir, keeping the available current for the circuit at a happy level . . . however . . . I still don't understand how one determines just how big a cap is needed.  The Son of Screamer uses a 47uf cap, but I have seen caps as big as 220uf on other designs.
  >>>These are PS filter caps, some cct.s benefit from larger Uf values, I generally use 100uf. They reduce PS noise only. Must be electrolytic [they're not in the signal path] because other types [maybe Tants come in big Uf values] don't go that big a Uf Value.

Also . . . the SOS has a polarized 1uf cap on the output of the effect . . . can a non-polarized cap be used in it's place?

>>>Sure...as long as the voltage rating of the cap is  = to or larger than the voltage of the PS. ...and have the advantage of being non polarized, cap orientation is required with polarized caps.

[gotdabluz]

Thanks . . . I guess I learn more 'n more all the time . . .

Some of the annonations I read said that the caps across the rails of the Voltage divider network were for power reservoir but did not mention noise reduction . . . but who am I to argue . . . I know next to nothing

I actually plan of using a metallized poly 1uf cap for the output . . . I am sure what is out there is rated at least 50v or better, so I guess that shouldn't be an issue.

Thanks again