It possible to substitute a 47uF NP cap with an electrolytic in a Boss FA-1?

[gigimarga]

Hello,

I want to build a Boss FA-1 clone and i saw that it uses a 47uF NP cap (which is impossible to find here at a reasonable dimension...only at 2000V for motors)!!!

So, the question is, can i replace it with a 47uF electrolytic? If yes, where the "+" will go and where the "-" will go?

The schematic is at http://www.schematicheaven.com/effects/boss_fa1_fet_amp.pdf

Thx a lot!

[John Lyons]

Most caps over 1uf are electrolytic.
You can get electrolytic non polar caps which is what boss used.
Since the cap is non polar the polarity does not matter...

john

[MarcoMike]

first a question...why would you build this one?!? anyway... the answers:
my guess would be that any large NP cap would work, like 20uF... but I found out it's apparently quite easy to find a "normal" 100V 47uF NP cap, at banzai's for exemple...

[Mark Hammer]

1) There IS no 47uf NP cap in the circuit.  It is 0.47uf.  Cheap and easily available in both nonpolarized and polarized form.

2) C2 (the cap in question) is placed in parallel with C3 to provide a combined parallel capacitance of .517uf....when R4 is bypassed.  When R4 is placed in series with C2, then the pathway is essentially C3, which results in more bass being rolled off.

Do you really need the C2/C3/R4 network?  Not really.  If you have no need for bass, and have concerns about 60hz hum, then ignore the switch and C2/R4, and use just C3.  If you need every last bit of bass, then ignore C2/R4 and make C3 470nf (0.47uf).

[MarcoMike]

  damn! shame on me, never reading schematics...

[Mark Hammer]

Trust me, that particular sickness has found its way from Italy to my city too!

[gigimarga]

Thx a lot all for your answers!!!

Mark, you're the eagle-eye-man
It seems to me that on the schematic the value is 0.47uF, but here http://ustomp.com/files/fa1buildetch.pdf, from where i got the PCB is written very clear that is a 47uF NP capacitor

Second, how it sounds this FA-1? I heard that Edge used it...that's why i want to build it

Thx again!

[RickL]

I have two of these, both bought when they were "used" not "vintage" and I've built one. It sounds fine as a clean booster and the tone controls are nice but I don't think it's any better than any number of other clean boosters. Depending on what you want to use it for an   LPB-1 might work just as well.

[gigimarga]

Thx Rick L...my favorite clean booster is Colorsound Power Booster (Overdrive) and MOSFET Booster.

[gigimarga]

I've finished it...sounds good (but not a must...) and has a lot of boost level.
As Mark Hammer suggested above (thx a lot again!!) i replaced C3 with 470nF to have the full bass always on.

Thx again all!

[ustompsteve]

I actually looked into this when I put together the layout.

On the original it is an electrolytic cap. I have included an image below. It is the electrolytic marked NP at the bottom.

I believe the dot is an artifact from photocopying. I assumed since the schematic specified NP and a voltage that it was an electrolytic.

It could be a .47uF electrolytic, I'm not sure why they would do that.

I was sure about it until Mark Hammer disagreed. He knows a lot more about this stuff than I do.

Does anyone have a real one that could take a look?

I will update my layout if we can figure it out.

--steve

[Boogdish]

The cap in question is drawn with the same symbol that the obviously polarized electrolytics in that schematic have (C10, C12, C4), which is a different symbol than the one which represents the obviously non polarized ceramic/film caps (c1, c3, etc).

I'd just try it one way, then the other with a polarized cap and see which way sounds better.  If neither work or sound good, you could try to replace it with two 100 uf caps back to back, making a polarized 50 uf (in theory).

[George Giblet]

It's definitely 470nF and non polar electrolytic because of the NP (common in Boss and Ibanez pedals.)

These days you would be better of using an mkt style film capacitor.  You can get a 470nF in a smallish package.

For example these are a 7.5mm lead pitch

http://export.farnell.com/avx/bq074e0474k/capacitor-470nf-100v/dp/1100594

and these are a 8.0mm lead pitch

http://www.jaycar.com.au/productView.asp?ID=RM7165&CATID=51&keywords=&SPECIAL=&form=CAT&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID=867