First post here, thanks for having me ,just an enthusiast bedroom player hoping to pick your brains about my idea for a specific wiring setup.
So my current setup is a strat, loaded with a kinman woodstock set with, dare i say this here, the k9 no soldering harness.(www.kinman.com/guitar-pickups/harnesses/harness-stratocaster/) What sold me on this is the switching setup wich is pretty versatile. It has 1 master tone, 1 master volume and one blend pot, to mix the neck pu in paralell with either the middle, bridge or both. The blend pot is a push-push pot wich when in "out" position changes the middle+neck from parallel to series. Now ofcourse the neck pu can be blended in in parallel. I really like this setup as it is very versatile and a lot of the combinations sound really nice.
Now why change a winning team? I just hate lugging around stompboxes on the occasions that i do jam so i'd thought why not add a fender mid boost circuit? The only downside for me is that i would like to be able to play "passive" as well, and the mid boost is always on. So i started looking for a way to defeat the active circuit without muting the guitar altogether.
I had a look at that diagram using an S1 switch, which uses three poles to switch between active and passive, and also cut the power.
I would think that what it does could be adapted to another wiring set up, such as yours, though I'm not familiar with exactly how the EC boost is designed. The switch could be any 3 or 4 poles switch, so a mini toggle is an alternative, or maybe a separate push button instead of one combined with a pot.
BUT, looking at how it is wired, I think there is a risk of massive THUMPs happening when you switch, since the power is being cut on and off instantly at the same time as the signal. The EC circuit may have a design that controls this, and it is easy enough to suppress the thump switching off, but I have found it very tricky to suppress the switch-on thump in a simple way. I am sure it is possible, just I don't know how and I've tried quite a few arrangements.
I think this issue is why stomp-boxes and active guitars do not have their power cut when going to off mode, even if all the electronics is bypassed. Power is only cut off when the jack is removed. Once everything is powered up and stable, then it is possible to switch smoothly and quietly between modes.
This thump problem is mainly an issue if you want to be able to switch while playing or with the amp switched on. But having to turn the amp down to change is a PITA, and its embarrassing or at least very noisy if you get it wrong!
I wonder how much current the EC circuit takes? We could estimate battery life if we knew, then decide if having it always on is really a problem, given that if battery ran down, you could still use passive mode.
Or just use a small stomp box, not much to lug really.
Thanks for answering! A thump would be a definite no-no, because having it on the guitar ofcourse means that it must be switched on-off while playing. i'll think about it some more, and until then just carry around my stompbox. Which is, indeed, not that big I guess i just love having me lots of buttons knobs and possibilites right on the guitar Thanks again, and if i decide to go for it i'll post back here!
It looks like JohnH already has you on the right track as far as your question is concerned. Let me just add that this "thump" issue isn't the switching between the active/passive circuits, but turning off the 9V at the same time. You could certainly implement what you want and just leave the battery connected.
As JohnH points out, if the EC circuit doesn't draw much, it may not be an issue. And, you could use a TRS (stereo type) output jack to disconnect the battery when the guitar is unplugged, just as with a stompbox.