Blending with a pot

[rangermaster]

Hi.

Question. I want to add a capacitor on a pot so i can blend the cap onto a other one.

I have a 4.7nf on my FX board and want to be able to mix a 22nf with it for range. So when turning the pot counter clockwise i only have 4.7nf and clockwise + 22nf(so 26.7nf). Is the wiring in the attachment correct ?

Thanks

[idy]

No, the pot is shorting out both caps.

Wire from one end of cap on board to terminal 3 of pot. New cap goes between terminal 2 and other end of cap on board. Now you have two caps in parallel with a resistor in series with the new cap, and you can make that resistor big or small.

[rangermaster]

Ok thanks. So like this..

[antonis]

[Phend]

Copied from an article on capacitors (very good) Beavis Audio Research
What about Variable Capacitors?
One of the first questions I had when I started building stompboxes was "I have variable resistors (potentiometers) all over the place. Why don't I have variable capacitors?" The answer is that they are limited to a very small capacitance and are quite expensive too. As such, they are not practical for stompbox usage.

Here's a trick to simulate a variable capacitor, especially useful for tone control applications. Attach two different capacitor values to a potentiometer--moving the wiper then sends more or less of the signal to one of the caps thereby changing the frequency response. Hare two approaches:

[rangermaster]

Copied from an article on capacitors (very good) Beavis Audio Research
What about Variable Capacitors?
One of the first questions I had when I started building stompboxes was "I have variable resistors (potentiometers) all over the place. Why don't I have variable capacitors?" The answer is that they are limited to a very small capacitance and are quite expensive too. As such, they are not practical for stompbox usage.

Here's a trick to simulate a variable capacitor, especially useful for tone control applications. Attach two different capacitor values to a potentiometer--moving the wiper then sends more or less of the signal to one of the caps thereby changing the frequency response. Hare two approaches:

This way its the same as IDY explained ?

[idy]

I suggested the first way. I see this more often on inputs.

The second that "pans" between two caps I see more on outputs (tone benders.)

[idy]

Wait, I think that first one is wrong or something else... it needs a second cap..in series with the pot. Two caps in parallel, one has a pot in series.

[rangermaster]

I found this just now..

[Phend]

I just found an article on capacitors, actually I was looking for something else. Seeing rangemasters topic is just a coincidence so I posted this part of the article, I have not tried or used either shown in the article, I myself am getting an education on this stuff.
Here is the link..
http://beavisaudio.com/techpages/capacitors/

[rangermaster]

I just found an article on capacitors, actually I was looking for something else. Seeing rangemasters topic is just a coincidence so I posted this part of the article, I have not tried or used either shown in the article, I myself am getting an education on this stuff.
Here is the link..
http://beavisaudio.com/techpages/capacitors/

Thanks! How do i exactly wire it on a pot what you send ? I'm not 'yet' good in reading those schematics .

[Phend]

On diagram 2, attach one leg of a cap on of the outside lug the pot, do the same with a different value cap on the other outside lug of the pot. Then connect the other legs of the caps to the tang of the output jack (not the ground tang). Now the middle lug of the pot (wiper) can be connected to the  circuit where the individual" fixed value cap is/was. I am not sure what the values of the caps should be. ?? Close or far ?? Help

[rangermaster]

Thnx that's really helpful.

It's for a treble booster. I need to mod it to make it a full range but with a variable pot/cap. So i think stock 4.7nf and a 22nf for the full range ?

[Phend]

Give it a try. Good Luck

[Phend]

rangermaster,
Please let the forum know how well your variable capacitor works out.!
Thanks for sharing if you can.