3PDT vs DPDT

[acidblue]

I've seen some schematics that use a DPDT footswitch instead of a 3PDT.
Is there a difference? Whats the advantage of using a 3PDT instead of a DPDT?

Does the 3PDT handle bypassing better?
Is the 3PDT just better quality?

Kinda curious about this since the DPDT are cheaper.

[jacobyjd]

3pdt gives you the ability to do true bypass with an LED on the 3rd pole. DPDT switches either use another method for lighting an LED (millennium bypass), or don't use an LED at all (or use a buffered bypass instead of true bypass).

[therecordingart]

I've seen some schematics that use a DPDT footswitch instead of a 3PDT.
Is there a difference? Whats the advantage of using a 3PDT instead of a DPDT?

Does the 3PDT handle bypassing better?
Is the 3PDT just better quality?

Kinda curious about this since the DPDT are cheaper.

DPDT - Double (Two) Pole Double Throw
3PDT - Three Pole Double Throw

|
|<- Bottom of a SPDT switch
|


| |
| | <- Bottom of a DPDT switch
| |

| | |
| | | <- Bottom of a 3PDT switch
| | |

The yellow section is where you connect the wire(s) that you want to switch. The yellow section connects to either of the red sections depending on the switch position. Think of the DPDT and 3PDT as two or three SPDT switches that have one lever to do the switching for all of them.

[Mark Hammer]

A brief history of pedals.....

1960's

• manufacturers make use of SPDT switches for foot-controlled devices
• musicians use maybe one pedal at a time and might, if they are a superstar, have 2 or 3 in series
• nobody notices the cumulative loading effects of having multiple pedals in series

1970's

• Alembic and others make everybody suddenly aware of signal quality
• regular musicians start to have more than 1-2 pedals in series
• DPDT switches introduced to disconnect effect inputs when not in use, and reduce loading effects
• manufacturers discover FET switching

1980's

• musicians start to have at least 4-6 pedals in series, many of them categorical duplicates (e.g., a fuzz AND an overdrive, a flanger AND a phaser)
• the birth of the pedalboard
• musicians come to value the role of a status indicator to identify which pedals are on or off

1990's

• Vintage pedal market begins to take off; older pedals are adapted to full/true bypass to avoid loading effects
• people still want status indication
• Mike Fuller gets some switches made for him that have an extra set of poles to handle status LED as well as bypass

That,s pretty much it.

[acidblue]

Thanks. that kinda explains things.

[darron]

you can't improve on Mark's runthough.


There are some diagrams here if you'd like to understand what is going on inside the switch:



http://www.dazatronyx.com/support/what-is-true-bypass/

[deadastronaut]

you can't improve on Mark's runthough.


There are some diagrams here if you'd like to understand what is going on inside the switch:



http://www.dazatronyx.com/support/what-is-true-bypass/

hmmmm i wondered why there were different wiring designs on 3pdt's...interesting..nice one darron.

[Processaurus]

Even if a circuit only calls for a DPDT stompswitch, I've started use one of the blue 3PDT's and leave a pole vacant, because they have a track record for more reliability mechanically than any the DPDT switches commonly available.

[Mark Hammer]

For me, one of the stronger arguments for using 3PDT switches (when I have some) is simply their smaller footprint.  It never ceases to amaze me how much of a difference in workable layout can be created by the slightly smaller footprint of the 3PDT.  Having lugs that point down instead of out can free up all sorts of space for position jacks and controls in more convenient ways.

[merlinb]

For me, one of the stronger arguments for using 3PDT switches (when I have some) is simply their smaller footprint. 

But... DPDTs are way smaller...

[Hides-His-Eyes]

Alpha baby

[darron]

Even if a circuit only calls for a DPDT stompswitch, I've started use one of the blue 3PDT's and leave a pole vacant, because they have a track record for more reliability mechanically than any the DPDT switches commonly available.

You can use some scrap wire as jumpers to duplicate one pole to the spare one for super reliability on that side

[askwho69]

i want to add hehehe DPDT is Softer than 3pdt i like DPDT because it doesnt latch as 3pdt 

[Electric Warrior]

A brief history of pedals.....

1960's

• manufacturers make use of SPDT switches for foot-controlled devices
• musicians use maybe one pedal at a time and might, if they are a superstar, have 2 or 3 in series
• nobody notices the cumulative loading effects of having multiple pedals in series

Nope. Many 1960's pedals have DPDTs wired for true bypass. There are countless examples, like all Tone Benders, Fuzz Faces, the early grey Vox wahs,...

[R.G.]

Try reading geofex - http://www.geofex.com/
In this case the pertinent articles include:
From 1998: The Technology of Bypass Switching: http://www.geofex.com/Article_Folders/bypass/bypass.htm
From the 90s, have to look up the date: Stomp Switch Wiring: http://www.geofex.com/FX_images/stompsw.gif
Why does my stompbox pop when I hit bypass? http://www.geofex.com/Article_Folders/box_pop.htm
and some related stuff:
From 1999: The Millenium Bypass: http://www.geofex.com/Article_Folders/Millenium/millen.htm
From Premier Guitar (and me): http://www.premierguitar.com/Magazine/Issue/2007/Dec/Should_You_Bypass_True_Bypass_Again.aspx

[electrosonic]

Even if a circuit only calls for a DPDT stompswitch, I've started use one of the blue 3PDT's and leave a pole vacant, because they have a track record for more reliability mechanically than any the DPDT switches commonly available.

I have never seen a datasheet for a 3PDT. I have one for an Alpha DPDT (107-SF12020F-L) its "life cycle" is stated to be 10,000 cycles. ( 10 x a day for about 3 years). I would expect the 3PDT would have worse specs, being more complicated / more parts.

Anyone have a datasheet?

A.

[Hides-His-Eyes]

Even if a circuit only calls for a DPDT stompswitch, I've started use one of the blue 3PDT's and leave a pole vacant, because they have a track record for more reliability mechanically than any the DPDT switches commonly available.

X wing maybe, but not Alphas.

[deadastronaut]

i like alphas...much better switch imo...shorter action too......

less 'clunky' than 3pdt's for sure!.....

[darron]

sometimes i like a good clunk....

[egasimus]

spdt + relay