Some more switch qs...

[Drake120]

Yeah.. hope you guys don't get bored with it

First: the picture refers to Small Stone, but in fact it can be used to switch any "two-leads" part:


Buuut... isn't the SPDT method some kind of a "non-true switching"? Isn't the second part changing the tone when first part is selected because of the "shared" lead? So, if I can, is it better to use the first method?

And second: how does the switches with "off" positions work? For example, look here, at the "AMZ fat mod": http://www.generalguitargadgets.com/pdf/ggg_its8_mods.pdf
I understand the "off" position - the signal just doesn't go through the switch and goes through the C3. But in the "on" position, what makes signal go through the switch and stops it from going through the C3?

And third: more practical one. I want to have something like that:
There are two points, A and B. Basically, I want to have them connected with each other or not :]
three position switch:
1st pos - signal doesn't go from A to B
2nd pos - signal goes from A to B through a potmeter
3rd pos - signal goes from A to B through a LDR

What type of switch should I use and how to wire it?

Thanks, JS

PS Hope that this is one of my last "switch" questions You guys really help!

[Mark Hammer]

You can change cap values by using parallel addition, series addition, or "substitution" switching.  Typically, the smaller the capacitance value you are trying to achieve, the more difficult it will be to come up with a suitable parallel combination that gets the precise value you want.  In those cases, it is often easier to switch between this cap and that one.  As the value starts to get larger (e.g., greater than .033 or so) it starts to become easier to acheive a specific cap value siply by adding another cap in parallel to an existing one.

For series caps, placing 2 or more caps in series always produces a lower effective value.  Shunting one or more of those series caps (by using a toggle to add a wire in parallel to that cap) will raise the effective capacitance.  Unfortunately, getting several caps in series to produce a desired outcome can be tricky sometimes.  In which case some prefer use of an either-or sort of switch to select between known cap values.

They all "work".  Which is more convenient in each case will depend upon your needs.

[Drake120]

(NOOB ALERT)

First, I made a mistake: I wrote "So, if I can, is it better to use the first method?" instead of "So, if I can, is it better to use the second method?". Sorry for that.

Tell me if I understood you well: I want to have a switch between, for example, two caps. In 1st position signal goes only through the first cap, in 2nd it goes only thruogh the second one. And I'm asking if the "DPDT method" as shown above is better than the "SPDT method". I'm thinking about it because the SPDT method reminds me of non-true bypass, which can cause some problems with sound. So, according to that sentence: "In which case some prefer use of an either-or sort of switch to select between known cap values", I should use a DPDT method, because both of the caps are known values... yes? Or am i way off target?

And, what about my other two questions?

Thanks for help

[Gus]

If you only want to switch two values all you need is a SPST

Find the two values you want.   Wire the smallest in all the time and add another cap in parallel to equal the larger value wanted.  One end of each cap will be wired together and the one to add will be switched in.
Caps in parallel add the values together.  Each value can be more than one cap.

[joegagan]

 i like this approach also (what gus said) the smaller cap gets 'swallowed up' somically, more or less by the larger one, and since it takes less wiring and a simpler switch it is a double plus. but in some cases or circuits the more complicated ways might need to be used.  for me too many caps in parallel sometimes causes a scratchy volume pot condition, i guess the dc isn't being blocked correctly.



some people believe (including  the late ken fischer of trainwreck amps, as he told me on the phone once) that the tone of a circuit can  sound richer in harmonics when more than one cap is run, as in parallel caps. he felt that the subtle phase relationship in the different cap reaction times caused this. that's the best way i can paraphrase from memory, but that was the gist of it.

how many gists make a gross of gists? is that how to spell gist?

[Drake120]

Thanks to you all

I'm gonna wire it the way Gus wrote. Still, I'm just curious whether the SPDT method really switches between the two caps. Anyway, thank you

But I'm waiting for the answers to my other questions, especially the third one

Cheers

JS

[joegagan]

in the fat mod you linked to,  your question
QUOTE
But in the "on" position, what makes signal go through the switch and stops it from going through the C3?

nothing, but the signal follows the path of least resistance and essentially renders the cap meaningless to the circuit.

your other q about the spdt in the small stone diagram, it is a legit way of switching between caps, in almost all circuits there is no problem having an open leg going to an unconnected cap ( the one that is left off in each position)

gus' method is not the same. he is adding a cap in parallel to the one that stays in circuit all the time. the circuit 'sees; the larger cap in most cases, making the sound of the two together in parallel very similar to just the larger one by itself ( assuming the larger cap is considerably larger than cap # 1 , which is logical since most of this cap switching is to make tone changes)

so, to answer your 3rd Q, if you want all that on one switch, you would like to use an on/on /on dual pole three position switch.
it is easy to figure out how to wire it, use a continuity checker and do your homework, you've got it. i can tell from your posts you understand it.

[Drake120]

Thank you very much Now everything is clear to me.

I was thinking about some DP3T's instead of a simple way of using on-on-on DPDT.

Thanks for all your help, and I hope that finally I will post any of my builds here to show you how useful your advices were