Help needed finding a small DPST switch - confused!

Horsebox · 28th March 2011, 02:22 PM

Hello,

Sorry, this is really basic. I'm looking for a small low-current ON-OFF switch for two channels of audio - I thought this was a DPST switch, but can't seem to find what I'm looking for at all, leading me to think I'm barking up the wrong tree.

Can anybody help me please?

Cheers!

rknize · 28th March 2011, 04:17 PM

So you want to switch two channels on and off, not switch between two channels? That sounds like a DPST to me. At DPDT switch, which is more common, will also work fine; just don't use the extra pole in the "off" position.

Horsebox · 28th March 2011, 04:42 PM

Thanks Russ,

Correct, I was looking for switches for UL/triode mode and cathode feedback on/off for the Simple SE, and assumed it wouldn't be a problem to obtain DPST toggles switches to do this - but was drawing a blank (apart from some large, high-current ones). I guess I'll use DPDT switches with the centre position redundant then, if that is common practice...I appreciate the help.

Mark

DF96 · 28th March 2011, 05:20 PM

Centre position? Most toggle switches only have two positions. Just a few have an additional centre position.

For UL/triode switching you need DPDT, and check that the switch will handle the voltage. Most mains switches will be OK, unless you have unusually high HT.

Horsebox · 28th March 2011, 06:09 PM

Quote:

Originally Posted by DF96

Centre position? Most toggle switches only have two positions. Just a few have an additional centre position.

I assumed that by definition all DPDThrow switches would have three positions i.e. on-off-on. Is this wrong?

I have ordered a set of DPDT switches rated at 2A, 250VAC. I plan to use them for cathode resistor swap, cathode feedback on/off and triode/UL switching. Obviously there's no problem with current ratings here, but have I underspecified the voltage? B+ will be 450V max.

Help much appreciated before I give myself a shock!

Mark

DF96 · 28th March 2011, 06:21 PM

No, most DPDT are on one side, or on the other side. If you want a centre-off position then you have to choose a switch which includes that - most don't. Some of these will switch the two poles separately, so the centre position will have one pole one way and the other pole the other way - you need to read the catalogue or datasheet carefully.

Strictly speaking, 250V AC is only good up to 350V DC but most switches will have a safety margin. Best to do the switching while the amp is switched off.

tomchr · 28th March 2011, 10:34 PM

A DPDT switch is most commonly an ON-ON switch. I.e. you flip it one way and one pair of switches is on. You flip it the other way and the other pair of switches is on. If you leave the second pair of switch poles disconnected, you'll have a DPST switch.

There are some DPDT switches that have a center position. Those are commonly referred to as ON-OFF-ON switches. They work like any other DPDT switch except for the center position where both switch pairs are off.

~Tom

ArtG · 29th March 2011, 01:34 AM

When you order switches, there is one other consideration to keep in mind. There is a DPDT switch with a temporary position that could be easily confused with a regular one. It is usually listed as ON-OFF-(ON).

Richard Ellis · 29th March 2011, 03:27 AM

Another consideration when buying switches is the two different nomenclatures of the contact "logic". First one is "Break before make", Second is "Make before break". This refers to the 'logic' of the contacts..........If this is confusing, a contact cannot be instant....as NOTHING exists that is instant.There is a time factor as you flip the switch whereby the First version will break the first contact before engaging the second contact "Break before make". The second will bridge all three contacts before disengaging the first set of contacts "Make before break". Some circuits cannot stand to be open in the first case, nor can some circuits be bridged in the second instance.

__________________________________________________ ______Rick..........

DF96 · 29th March 2011, 10:59 AM

I think it would be unusual for a toggle switch to be MBB. This issue normally only relates to rotary switches.

28th March 2011, 02:22 PM	#1
Horsebox diyAudio Member Join Date: Jan 2011	Help needed finding a small DPST switch - confused! Hello, Sorry, this is really basic. I'm looking for a small low-current ON-OFF switch for two channels of audio - I thought this was a DPST switch, but can't seem to find what I'm looking for at all, leading me to think I'm barking up the wrong tree. Can anybody help me please? Cheers!

28th March 2011, 04:17 PM	#2
rknize diyAudio Member Join Date: Feb 2009 Location: Chicagoland	So you want to switch two channels on and off, not switch between two channels? That sounds like a DPST to me. At DPDT switch, which is more common, will also work fine; just don't use the extra pole in the "off" position. __________________ Russ http://www.knizefamily.net/russ/cate...ics/tubeaudio/

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28th March 2011, 04:42 PM	#3
Horsebox diyAudio Member Join Date: Jan 2011	Thanks Russ, Correct, I was looking for switches for UL/triode mode and cathode feedback on/off for the Simple SE, and assumed it wouldn't be a problem to obtain DPST toggles switches to do this - but was drawing a blank (apart from some large, high-current ones). I guess I'll use DPDT switches with the centre position redundant then, if that is common practice...I appreciate the help. Mark

28th March 2011, 05:20 PM	#4
DF96 diyAudio Member Join Date: May 2007	Centre position? Most toggle switches only have two positions. Just a few have an additional centre position. For UL/triode switching you need DPDT, and check that the switch will handle the voltage. Most mains switches will be OK, unless you have unusually high HT.

28th March 2011, 06:21 PM	#6
DF96 diyAudio Member Join Date: May 2007	No, most DPDT are on one side, or on the other side. If you want a centre-off position then you have to choose a switch which includes that - most don't. Some of these will switch the two poles separately, so the centre position will have one pole one way and the other pole the other way - you need to read the catalogue or datasheet carefully. Strictly speaking, 250V AC is only good up to 350V DC but most switches will have a safety margin. Best to do the switching while the amp is switched off.

28th March 2011, 10:34 PM	#7
tomchr diyAudio Member Join Date: Feb 2009 Location: Greater Seattle Area	A DPDT switch is most commonly an ON-ON switch. I.e. you flip it one way and one pair of switches is on. You flip it the other way and the other pair of switches is on. If you leave the second pair of switch poles disconnected, you'll have a DPST switch. There are some DPDT switches that have a center position. Those are commonly referred to as ON-OFF-ON switches. They work like any other DPDT switch except for the center position where both switch pairs are off. ~Tom

29th March 2011, 01:34 AM	#8
ArtG diyAudio Member Join Date: Nov 2006 Location: Central PA	When you order switches, there is one other consideration to keep in mind. There is a DPDT switch with a temporary position that could be easily confused with a regular one. It is usually listed as ON-OFF-(ON).

29th March 2011, 03:27 AM	#9
Richard Ellis diyAudio Member Join Date: Sep 2006 Location: Mar del Plata, a BIG seasonal getaway city, can see the Ocean from our residence.	Another consideration when buying switches is the two different nomenclatures of the contact "logic". First one is "Break before make", Second is "Make before break". This refers to the 'logic' of the contacts..........If this is confusing, a contact cannot be instant....as NOTHING exists that is instant.There is a time factor as you flip the switch whereby the First version will break the first contact before engaging the second contact "Break before make". The second will bridge all three contacts before disengaging the first set of contacts "Make before break". Some circuits cannot stand to be open in the first case, nor can some circuits be bridged in the second instance. __________________________________________________ ______Rick..........

29th March 2011, 10:59 AM	#10
DF96 diyAudio Member Join Date: May 2007	I think it would be unusual for a toggle switch to be MBB. This issue normally only relates to rotary switches.

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