Help Figuring out Switches

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Weathered
Posts: 67
Joined: Thu Jul 26, 2007 7:10 pm
Location: St. Paul, MN

Help Figuring out Switches

Post by Weathered »

First, apologies for being a complete neophyte with regard to some of these things.

So.....

I'm planning some switching in my next build, and want to be sure I understand switch terminology.

I'm planning to add a boost, which will switch in and out a cathode cap on V1b. I'm guessing I need a SPST on-off. Something like this (can I use a SPDT as a SPST by leaving one end disconnected?):

http://www.tubesandmore.com/scripts/fox ... tem=P-H540

Also planning to put in a cathode/fixed bias switch. From what I've seen, that requires a DPDT, but a 2 position (as you don't want a center off, but rather an on-on). Would this guy do the trick?

http://www.tubesandmore.com/scripts/fox ... tem=P-H527

Also planning to put a switch in for NFB (thinking of being able to switch to a higher or lower NFB resistor value, with the center position turning off NFB). Thinking that this requires a SPDT on-off-on. Would this one work?

http://www.tubesandmore.com/scripts/fox ... tem=P-H496

Apologies for being so needy - I've never used anything other than a standard SPST on-off switch for power and standby.
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xtian
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Re: Help Figuring out Switches

Post by xtian »

Yup, yup, yup.
Weathered
Posts: 67
Joined: Thu Jul 26, 2007 7:10 pm
Location: St. Paul, MN

Re: Help Figuring out Switches

Post by Weathered »

Perfect. Thank you.

Also, while I'm at it - I want to make the MV defeatable, and I figure I can do that by lifting the ground. Most of the push-pull pots I've seen close contacts when pulled, rather than opening contacts. Could I use a DPDT Alpha like below to lift the ground on the MV (or the mid pot if I wanted to put a tone-stack defeat in the circuit as well)?

http://www.tubesandmore.com/scripts/fox ... =R-VPP-1MA
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Structo
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Re: Help Figuring out Switches

Post by Structo »

Those push pull pots are usually double throw so you can have the switch closed when pushed in or closed when pulled out.
Depends which set of terminals you use.
Here is a diagram of a DPDT switch.
The terminals at the left are the two terminals in the middle of the switch.
The four terminals on the right are the two terminals on either side of the middle ones.
Hope that doesn't confuse you more. :lol:

[img:128:119]http://www.kpsec.freeuk.com/symbols/swdpdt.gif[/img]
Tom

Don't let that smoke out!
Weathered
Posts: 67
Joined: Thu Jul 26, 2007 7:10 pm
Location: St. Paul, MN

Re: Help Figuring out Switches

Post by Weathered »

That makes perfect sense. I think I know exactly how I could wire that up - may be overkill, but I'm all about overkill....:)
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