expression pedal bypass.

[cjkbug]

     Have any of you guy's ever included an expression pedal input jack on any of your projects. I'm researching it at the moment and wonder if anybody has pulled it off. What I'm thinking of doing is using a stereo double switching jack to bypass a dual gang panel mounted pot with the same pot mounted in a wah shell. there are 3 connections to the pot. I'm thinking the switching jack will bypass the pot when the cable is inserted, and reconnect the pot when it's removed.

My questions are:
1. Is a double switching jack the right part or do I need something else?

2. is it necessary to have the control in the pedal disconnected when the pedal is connected, or can I simply "add another pot" into the circuit?

Any thoughts? I had been working on the project for a while before the Idea  came to me, and I have a general Idea of how to go about it. but this is a first for me and I'm sure that there is the possibility of a more elegant solution. I want to try to get the theory ironed out before I take too much of a detour. I'm still waiting on the enclosure and a few other parts so I'm doing my homework now.

If any body has done any expression installations. any Ideas help. schematics, drawings, or gutshots would be dandy. thanks guys.

[gtr2]

Yes an isolated stereo switched jack is what you want.  I use mouser part # 550-nmj6hcs
http://www.mouser.com/ProductDetail/Neutrik/NMJ6HC-S/?qs=tdfQxhgBXr8%252bLeL3kwf5rw%3d%3d

You hook up the pcb wires for the pot to the jack first then connect the wires from the switched section of the jack to pot.  When you plug in your stereo cable it will bypass the pot in the pedal and your expression pedal will "be the pot" per say.  Then when you unplug your cable the pot will be "active" again!

Here is an example.  Its hard to see exactly what I'm talking about but the wires for the pot go to the jack first then from the jack to the pot.



Hope this helps.  It's a really easy mod to do.

Josh

[cjkbug]

your referring to the pot in the middle right? that's what I was thinking pretty much exactly, except I ordered an open framed switchcraft jack. I think I need the one you have as the ground lug is switchable and the jack is insulated. thanks for clarifying.

[gtr2]

Yeah, you need the jack totally isolated from the enclosure.

[rps-10]

I'm trying to do this with a Karate Chop's (Harmonic Energizer) "Centre Frequency" control pot.

I can't quite figure out how to get it correct. So far the closest I've got is some slight variation in "frequency" but a huge amount of noise or a major scream when plugging the lead into the expression bypass jack.

Was wondering if I'm correct in thinking :

Pot Lug/PCB 1 = Ground/Sleeve
Pot Lug/PCB 2 = Tip
Pot Lug/PCB 3=  Ring




I have a moog and Berhinger FV100 Volume/Expression pedals,with the Behringer giving the best results so far.
Just a gentle nod in the right direction would be helpful as this is driving me nuts so far. 

--also been told I could use a "mono" version of one of these insulated jacks instead.

[gtr2]

I believe the FCV100 has a 50k pot that's why it seems to work better.  But you need to open up the FCV and modify it I believe.  I'm not familiar with that model but most volume pedals when "tilting back" send signal to ground, that's how it's adjusting the volume.  You'll have to disconnect it from ground and you should be able to make it work with a standard mono cable using the tip and ring.  Hope that helps, it can be confusing with the explanation. 

Josh

[rps-10]

Thanks, I knew the FCV100 would be ok without modification as I've seen it used on another builders version of a HE.

Anyway last night I got it all working with a mono jack & patch lead.

For info for other newbie builders/meddlers like myself on this build it was the follwoing configuarion that worked:

Pot lug/PCB 3: Jack Sleeve
Pot lug/PCB 2: (straight through)
Pot lug/PCB 1: Jack Tip

Just need to paint it etc now it's be put in a new bigger case