# LEPRECHAUN(EQD  rainbow machine clone) what Potentiometer value for diy EXP Pedal?



## mikef (Aug 22, 2020)

Hello! Well I have a ton of wah and vol shells, so I am wanting to DIY an expression pedal.
What value should be the Potentiometer? also, audio taper or  log taper? Thanks!


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## Cybercow (Aug 22, 2020)

mikef said:


> Hello! Well I have a ton of wah and vol shells, so I am wanting to DIY an expression pedal.
> What value should be the Potentiometer? also, audio taper or  log taper? Thanks!


My Leprechaun PCB arrived today and I was wondering that same question myself after printing out the schematic and build docs. The build doc didn't have the schematic, but I found it here in the forums. Just to the right of IC2 (the FV-1) in the schematic, you'll see 3 connections labeled "T", "R" & "S". The "T" is connected directly to pin 20 of the FV-1. And below those 3 connection points, you'll see the "Pitch" pot wiring. That's also the external expression control.



Based on the schematic, BOM and close examination of the PCB, it appears that the top-center pot (labeled as "Pitch" in the schematic, but labeled "Spectrum" in the BOM is a B50K) as the value used for the external expression control. You could experiment with the different tapers if you want; but I suspect the B50K will do just fine.

Just a head's up, "audio taper" and "log taper" are the same thing- usually annotated as "A". 
A "reverse log taper" or "anti-log taper" are the same thing - usually annotated as "C".
But in this build, the "Pitch" control calls for a B50K which is linear.

Good luck with your build.


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## Robert (Aug 23, 2020)

Any value from 10K to 500K should work fine so just use what ever will be the most compatible with your other pedals.


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## Cybercow (Aug 23, 2020)

Robert said:


> Any value from 10K to 500K should work fine so just use what ever will be the most compatible with your other pedals.



Your answer is simpler and covers a wider range than I suspected. Thanks!


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