Karate Shop Expression?

[eldanko]

Howdy friends -

I'm toying with the idea of building a Karate Shop with an external expression pedal for the freq knob, a la the Godlyke Triskelion.  How difficult would it be to add an expression pedal jack that was only engaged when a cable was plugged into it?  In other words, if nothing was plugged into the jack then the freq knob would be active, but the knob would be replaced by the expression pedal when connected?

[jkokura]

If you used a switching jack that isolates from the enclosure you could do it I think. I'm not sure about which expression pedal you'd need though, but I'm not sure if any of them use A50K pots... The switching jack is important. The switches build into the jack would connect the pot to the board when no plug is in the jack, and bypass that pot when you plug in, essentially replacing the onboard pot with the one built into the expression pedal.

I suspect you'd have to build an expression pedal specifically for your pedal. You could try another type and see if the change in pot value works fine. Not to mention needing to verify which lug of the switching jack should go to which lug of the pot...

Jacob

[stecykmi]

I've never tried this, but how about putting a resistor in parallel to the expression pedal to change the resistance? You could hook it up across the jack of the karate shop so wouldn't need to mess with whatever expression pedal you're using.

For example, if you're an exp pedal with 250k and you need 50k, use a 62k resistor in parallel (68k will work fine).

[eldanko]

Challenge accepted.  Thanks for the help guys.  I am going to explore this a bit further...

[rps-10]

Done it here:

http://www.madbeanpedals.com/forum/index.php?topic=3289.0

[eldanko]

Perfect!  And it worked well?  I may hit you up for a crude wiring diagram if you get a chance.  I have a couple of those plastic jacks lying around that would be perfect for this. 

[rps-10]

yeah it works fine, nearly killed my hearing when testing the combination of wires out though lol

I used a "mono" jack, (just couldn't figure out how to use a "Stereo" jack) one of those Cliff jacks that cut the connection when you plug in a lead.

Mono patch lead to a Behringer FCV100 -- which has a 50K pot inside it  

I have my wiring solution in another thread here. I'll find it in a mo....


here:  http://www.madbeanpedals.com/forum/index.php?topic=2037.msg32556#msg32556

I have the pedal all apart again now as I'm painting it, and then will try my first ever go at a "decal"  then will do a demo  

[rps-10]

Also, word of warning - don't expect a Madbean Karate Chop to sound anything like a Triskelion.
The TWA Triskelion is a Harmonic Energizer on acid kind of thing. There is plenty more going on in that box then just the old HE circuit.
I'd guess they have a few boosters added in there and maybe even a fuzz to get all that noise out of that box.

[eldanko]

Oh, I certainly don't.  I found a gut shot of one of those at one point... that thing is certainly capable of some pretty nutty gain.