Implementing an expression pedal hook-up

All frequent questions on switching: true or not true bypass, transistor-based or mechanical.
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culbuto
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Post by culbuto »

I'm building an Anderton Super Tone Control on veroboard from the genious lVlark's blog http://tagboardeffects.blogspot.fr/2012 ... ntrol.html

Do you know how I could implement an input so I could control the filter frequency with an EP2 pedal from Moog ?
Here what the Moogerfooger's manual tells about the pedal inputs.
'All pedal control input jacks are 1/4" tip-ring-sleeve phone jacks. The sleeves are grounded and the ring terminals are supplied with +5.7 volts which is current-limited to about 0.5 milliamperes. The tip terminals receive the variable voltages from the pedals.'

And here is a pdf that show the details about the pedal itself.
http://www.teaser.fr/~amajorel/ep2/

Thank you in advance. And sorry for my ignorance.

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Nocentelli
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Post by Nocentelli »

I don't think it is possible: The Moog exp pedal is a 100k pot, whereas the frequency pot on the Anderton circuit is a 10k. Now, you could get around this problem with a pair fixed resistors in parallel with the pot connections to reduce the effective resistance of the exp pedal pot. However, the Anderton circuit specifies a dual-ganged 10k pot, i.e. TWO voltage dividers controlled by a single common shaft: You cannot replicate this with the single pot used in the Moog exp pedal.

If you want to build a filter pedal controlled by an expression pedal that is a bit more than a simple wah sound, I've had some success with the EHX Bassballs converted to use an expression pedal to control the sweep (aka the Hairyballs, by Ronan), and I'm currently working on a vero for a OTA-based lowpass filter with resonance from a schematic by Eric Archer, using an exp pedal to control the cut-off frequency. Both circuits use a 10k pot (which is handy, sinceI've got a Roland EV-5 which has a 10k pot) but you could easily add 5k6 resistors between the wiper and outer lug connections to your 100k pot to get 10k-ish:

Hairyballs:
https://www.freestompboxes.org/viewtopic ... 28&t=19437

Eric Archer's LPF
https://www.freestompboxes.org/viewtopic ... 28&t=20140
modman wrote: Let's hope it's not a hit, because soldering up the same pedal everyday, is a sad life. It's that same ole devilish double bind again...

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culbuto
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Post by culbuto »

Thank you very much Nocentelli.

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