How to Wire a Variable Capacitor?

[perro5151]

Hello, everybody.

I decided to put up a post on this because a search of the inter-web didn't really bring notable results...

On my first pedal build, I stumbled on a lucky/happy accident. I was building an NPN Fuzz Face and wired the 2.2uf cap as a variable capacitor and voila! It worked great as a Bass control (50k Lin pot). I wired it with the capacitor ( - side of the cap from the input) tied to Lug 2, and the hole where the + side of the cap would've gone wired to lug 3.

Here is where my question enters in. This worked great with a large value cap (such as is used in the Fuzz Face), but with smaller value caps it is hard to notice the addition of Bass when turning the knob... Is this because the value of the capacitors are too small, or because I'm using too large of a pot value (25k)? Or perhaps, as is very possible, that first 'bass' control in my fuzz face was a fluke and I am actually wiring these variable capacitors incorrectly...

Thanks in advance!

[reneshelle]

If I understand you correctly you made a normal hi-pass (bass cut) filter. See the attached file.

The size of the cap (and pot) affects the frequencies that are cut. Perhaps you can have at look at this site

http://www.muzique.com/schem/filter.htm

to do some calcutations...

Hope it helps

By the way. The attached picture is taken from Brian Wamplers advanced DIY effect pedals book

[perro5151]

I wired mine up differently, but like I said, happy accident... Thanks for the information!