3 way input cap switch ....how to wire?

[Solidhex]

Yo

  I couldn't find any previous posts that discussed this... How would one wire a 3 way dpdt on-off-on switch to toggle between 3 different input caps/what have you, before hitting the circuit board? I got this switch from small bear http://www.smallbearelec.com/Detail.bok?no=41  . Any help would be appreciated!

--Brad

[DocHeavy]

Capacitor B needs to be the smallest targeted value as it will always be in the circuit. Since it will always be there, it will add to each of the other values that you switch in - so you need to reduce those outer caps by the value of the middle cap.

For example, let's suppose you want to switch 2.2nF, 3.3nf, and 4.7nF.

2.2nf needs to be in B position.

Position A needs 1.1nF (3.3nf targeted value minus 2.2nF in position B). When cap A is switched in, cap A and cap B will be in parallel - adding the 2 values - yielding 3.3nF.  (1.1nF + 2.2nF)

Position C needs 2.5nF (4.7nf targeted value minus 2.2nF in position B) yielding 4.7nF when switched in. (2.2nF + 2.5nF)

Hope that made sense.

[soulsonic]

That's how I do it. Works like a charm.

[Solidhex]

You guys rule thanks!

--Brad

[CaptainLark]

Im having trouble with this at the moment.
I have wired it up as this diagram shows but am having no signal output from the middle lug. I dont understand what I am doing wrong.
If i used the wrong value capacitor would I have no output. I rewired it with another switch and it didnt work, so that wasnt the problem. I tested it with an audio probe.
Help!

[slacker]

It's possible if you used too small a value that the cut off frequency could be above frequencies you can hear then you would get no output. That's not very likely though, what circuit are you using this with and what values did you use?

[CaptainLark]

It is a DAM Meathead with switchable Caps.

http://tagboardeffects.blogspot.com.au/2012/02/dam-meathead-with-switchable-caps.html#uds-search-results

I tested it with an Audio Probe, and i am getting signal to the first DPDT switch from the Input. When i test the middle lug on the other side (going to board), the signal stops, and i am not getting anything after that. I have wired it exactly as the diagram says, and used the same cap on the middle lug and on the bottom (10n and 33n respectively). I have tried a different switch, so it must be something im doing wrong. Is there something im missing? I have been stuck with this for a couple of days, and it is beginning to annoy me! Any advice would be great.

[slacker]

Do you know that the circuit works? Are you sure it's a problem with the cap switch part.
Try disconnecting the cap switch from the the board and then test it with the audio probe.

[CaptainLark]

I havent tried that yet, but could give it a go.
The only reason i think it is the switch is because when I follow the circuit with my audio probe, the sound cuts out from the OUT of the first switch. I know that their should be no continuity between the two poles, but because they are connected by a soldered capacitor, how come the sound cuts out?