EVH Flanger Mod

[TheSwitchPedal]

Hi everyone,
I recently modded my EVH Flanger to include an expression pedal. A few weeks back, I noticed that if you set the width knob to zero, you would have a manual flanger controlled by the Manual knob (coincidence?? didn't think so ). So I decided to add an expression pedal jack that controlled that knob. I went down to my local hardware store and got myself an SPST 1/4 jack (I have no idea if they are named like this, but basically it is a jack that allow signal to pass through it when there is nothing plugged into it, but when you plug in a cable, the signal goes through the cable). I wired the jack to let the user use the manual knob as normal when there was nothing plugged into the jack, and when there was, use an expression pedal instead. When I finished building it I put it back together but forgot to install a small screw that apparently grounds the unit to the casing. It worked perfectly well and as I was cleaning up, I saw the screw, so I went to my flanger and installed it. I tried it once more and now the flanger didn't work. I thought this was weird and uninstalled the screw, now it's working again. What's going on?? For now I don't have the screw installed and it's working, but I would like to know what I did wrong.
Thanks

[Joe Hart]

Maybe the screw that grounds the circuit to the case, is causing the signal that you have running through the jack (which may have the signal going through the entire case, now) to ground out? Does that make sense? Is the jack that you added insulated from the metal enclosure?
-Joe Hart

[Fender3D]

The manual control sweeps from +Vcc and ground, providing a control voltage to a dedicated op-amp.
You need a stereo jack. Each of the 3 contacts must be tied, after switching, to the 3 lugs on the pot.
You can use the usual jack, like that in Marshall amps (6 contacts).
You'd better check which lug goes to ground and tie it to jack's ground tip.

Watch out, you can't have the same sweep of the manual with a pedal, 'cause its mechanical won't let you obtain the whole potentiometer coarse, unless you cheat somehow.

[TheSwitchPedal]

Thanks for your help,
The jack I bought only allowed me to switch the tip and the sleeve, therefore I decided to leave the ground connected to the potentiometers middle connection (I think this doesn't do any harm as the middle connection can only be connetced to the other two connector with the wiper. These other two connections are disconnected, so in theory you get an open circuit, well at least I think so). Back to the point, what was happening was that the middle connection of the pot was shorting to the ground via the casing. So i just insulated the casing from the jack with insulating tape and voila! the problem is gone! Now my next problem is getting an expression pedal. Would any of you reccomend a rather cheap but well made expression pedal?

[TheSwitchPedal]

Watch out, you can't have the same sweep of the manual with a pedal, 'cause its mechanical won't let you obtain the whole potentiometer coarse, unless you cheat somehow.

How can I hack an expression pedal?? I hope its a mechanical hack as I am not good with electronics. 

[Joe Hart]

What value is the pot you're "replacing"? A cheap wah has 100K, that you could easily bump down with resistors. Or if the pot you're "replacing" is larger, maybe you don't need the entire sweep of the pot?
-Joe Hart

[Fender3D]

any pedal that could bear a potentiometer is ok
just check it has a proper value (your target is 50K from min to max)

then it's a matter of taste

BTW
just in case... you should do a thing like this

[milosch]

I did this to my MXR flanger copy.  I haven't used it much but it is a nice effect.