Dumb Collosalus cap question

[blearyeyes]

Can I swap 15uF @C13 and C14 with another value, Like 22uF?

They're electro caps, looks like they might be there to stop ocillation ? Both negative sides connected together, in series, positives to parts of the LFO control circuit. A8 on schematic.

[blearyeyes]

http://www.madbeanpedals.com/projects/Collosalus/docs/Collosalus.pdf

Link to docs

[blearyeyes]

Well I put them in and will see!

[Scruffie]

They together form a poor mans NP cap, as 2 caps in series divide, close enough would be 33uF & 10uF.

[blearyeyes]

So it's not about a polarized cap but just a cap with a certain Micro Farad rating?


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[Scruffie]

So it's not about a polarized cap but just a cap with a certain Micro Farad rating?


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Yup, think of it as your LFO 'range' cap, setting how long a swing the LFO can have, if you used a 1uF NP, you'd only get very fast rate settings.

[blearyeyes]

Thanks Scruffie...

[blearyeyes]

Ok bi-polar cap or NP cap @1uF is what is called for when it's 15uF/15uF in series. So 22uF/22uF would be the same...1uF
The way it is now I only get oscillation over 1/4 of the range of the pot...


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[Scruffie]

No... 15uF & 15uF in series is 7.5uF.

33uF & 10uF like I suggested would be 7.674uF, so you'll actually get a tiny bit more range.

I don't know how you got 1uF (in fact I mentioned what would happen up there, you're only getting the very fastest of the range) but that's why you have no range practically.

[blearyeyes]

At the moment it is as you suggested. 33uF & 10uF.. I'm lacking basic math information regarding electronics. I guess I'll have to look this up and get it straight..duh!


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[Scruffie]

Are you using the correct value and taper pot?

I'm a bit confused, where did the 1uF bit come from if you're using 33 & 10uF?

[blearyeyes]

My bad. Got my Electronics Assistant program going and figured it out. The 1uF came out of my addled brain..sorry.

Yes I have the proper pot and am only getting oscillation speed control over 1/4 of a turn of the pot.. then the LFO stops. but I'm using the wrong opamp. Is the C rated pot audio taper or linear?

[Scruffie]

My bad. Got my Electronics Assistant program going and figured it out. The 1uF came out of my addled brain..sorry.

Yes I have the proper pot and am only getting oscillation speed control over 1/4 of a turn of the pot.. then the LFO stops. but I'm using the wrong opamp. Is the C rated pot audio taper or linear?

A C pot is reverse audio, so you can use an audio taper wired backwards but the pot will work backwards... if it's stalling though sounds like you still have issues though i'm afraid, but you're using an NE5532 correct? As I stated in the other thread, usually a terrible LFO OpAmp, the original 1458 or a 358 may solve the stalling issue.

[blearyeyes]

Yes NE5523..I should wait until I get a few 358s.
If you wire an audio taper pot backwards then it would work the right way wouldn't it? Or do you mean the taper will be backwards?


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[Scruffie]

Yes NE5523..I should wait until I get a few 358s.
If you wire an audio taper pot backwards then it would work the right way wouldn't it? Or do you mean the taper will be backwards?


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If you switch lugs 1 & 3 of an audio taper pot, the pot will work as a reverse audio pot but full clockwise will be the slowest sweep and full counterclockwise will be the fastest.