I've seen several different schematics on off board wiring for a 3pdt.
I like to know which one is correct?
Here are 2 that are common.
http://www.tonepad.com/getFileInfo.asp?id=76 (http://www.tonepad.com/getFileInfo.asp?id=76) Page 5 for 3pdt
http://www.beavisaudio.com/techpages/StompboxWiring/ (http://www.beavisaudio.com/techpages/StompboxWiring/)
I use the Beavis version, but with the LED on the middle pole rather than an outside one. I also ground the input through the left over lug.
Madbean uses another version, and I think GGG has even another version. Pick one you like and use it, they all are about the same. I've been told some have advantages over others, but I'm not sure of the details.
Jacob
Quote from: jkokura on September 15, 2010, 03:53:21 PM
Pick one you like and use it, they all are about the same. I've been told some have advantages over others, but I'm not sure of the details.
Jacob
Thanks, I like the beavis one also, seems to be the simplest one.
I always use this one (courtesy of darron) simply because it grounds the input when bypassed:
http://www.diystompboxes.com/smfforum/index.php?topic=56220.0
I'll admit I've never performed any tests to measure exactly how much of a difference this actually makes but I do sleep better at night knowing that freeloading rogue currents aren't amplifying themselves on my dime.
There are at least three ways to wire up a DPDT switch to do true bypass. That's because a DPDT is equal to two Single Pole Double Throw switches operated in parallel, and you don't need one of the throws. So it's possible to put the unused throw on the input or the output section. You can also use the "extra" throw to ground the input, or to connect a Millenium Bypass indicator circuit to the output. Or to just use up the extra pole with a shorting wire.
There is no "correct" one. They all do true bypass.
A 3PDT merely adds another SPDT switch section, of which only half is used, to work the LED.
About the only difference in the circuits in practice is whether the input is grounded or not. Some pedal circuits go nuts when their inputs are left open, producing noise and/or oscillation that can couple to the signal line from their output. Other pedal circuits don't have this problem, and whether their input is grounded or not makes almost no difference.
Good to know that's the only difference (the grounded input) :)