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PostPosted: Fri Nov 11, 2022 12:30 pm 
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Hello, first time user of a message board here. I was considering buying the Envelope Filter & Fixed Wah Kit. 1 thing that I wanted to do was modify it to have an expression out so I can use a foot pedal to get normal Wah sounds in the fixed mode. I should also mention this would be my first time building a pedal. Is this possible, how would I go about doing this, and would this be too difficult for a first timer? Thanks for any and all help.


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PostPosted: Fri Nov 11, 2022 1:06 pm 
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Rule #1 is always get it working without modifications first, so keep that in mind.

There is a fairly simple way to set up an option to switch between two pots for a selected parameter. You need an extra pot of the same value and an extra 3PDT switch. Instead of wiring the pot to the PCB, you run three wires to the middle three lugs of the 3PDT. Then you run three wires from the lower position to one pot, and three wires from the upper position to the other pot. Then when you actuate the switch, it toggles back and forth between the two pots.

In your case, the second pot is going to be inside an expression pedal, which is a little tricker. What you would need to do is install a TRS (stereo) jack to the enclosure and run one set of wires to the three lugs of the jack rather than to the pot itself. You'll use a TRS cable to connect that jack to your expression pedal. If you only ever want to use the expression pedal, you can just run the wires from the PCB to the jack and omit the standard pot.

Now, you can make this even cooler by using a switching jack instead of the 3PDT, so that inserting the TRS cable toggles the switch for you. This is quite a lot trickier to wire up in my experience, but it's very slick once you get it working.

To your question of difficulty, this kit is pretty good for beginners, and as long as you follow Rule #1, you don't really have a lot to lose. But this mod definitely isn't "easy" if you're new to pedal building, so proceed with some care. And I'd also point out that you're going to end up taking up the same amount of pedalboard space as having the envelope filter pedal and an actual wah pedal on the board, so… think on that.

As always, we are here to help!

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PostPosted: Mon Nov 14, 2022 6:08 pm 
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sjaustin wrote:
Rule #1 is always get it working without modifications first, so keep that in mind.

There is a fairly simple way to set up an option to switch between two pots for a selected parameter. You need an extra pot of the same value and an extra 3PDT switch. Instead of wiring the pot to the PCB, you run three wires to the middle three lugs of the 3PDT. Then you run three wires from the lower position to one pot, and three wires from the upper position to the other pot. Then when you actuate the switch, it toggles back and forth between the two pots.

In your case, the second pot is going to be inside an expression pedal, which is a little tricker. What you would need to do is install a TRS (stereo) jack to the enclosure and run one set of wires to the three lugs of the jack rather than to the pot itself. You'll use a TRS cable to connect that jack to your expression pedal. If you only ever want to use the expression pedal, you can just run the wires from the PCB to the jack and omit the standard pot.

Now, you can make this even cooler by using a switching jack instead of the 3PDT, so that inserting the TRS cable toggles the switch for you. This is quite a lot trickier to wire up in my experience, but it's very slick once you get it working.

To your question of difficulty, this kit is pretty good for beginners, and as long as you follow Rule #1, you don't really have a lot to lose. But this mod definitely isn't "easy" if you're new to pedal building, so proceed with some care. And I'd also point out that you're going to end up taking up the same amount of pedalboard space as having the envelope filter pedal and an actual wah pedal on the board, so… think on that.

As always, we are here to help!


Aside from making sure to get the pedal working without mods first, this isn't exactly the best advice.

This particular circuit uses a VCA( voltage controlled amplifier). So you could actually use a standard voltage divider expression pedal like a Roland EV-5. You'd still need to use a TRS disconnect jack. Sleeve to ground. Ring to +V. Tip to the pole of the manual toggle switch. You'd need to use the disconnect switch in the TRS jack to remove the toggle switch (which is ultimately removing the envelope trigger and manual pot) from the circuit when the expression pedal plug is inserted into the jack.

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Please do not PM me. email is prefered. keith@buildyourownclone.com


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PostPosted: Tue Nov 15, 2022 7:37 am 
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Interesting, thanks for the clarification, Keith.

If I understand correctly, this is due to the different electronic functions a pot can serve in an effects circuit. My method worked great when I used it on a tremolo pedal for toggling the rate control between a panel-mounted pot and an expression pedal. I assume that the rate control is wired as a variable resistor as opposed to a voltage divider?

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PostPosted: Tue Nov 15, 2022 4:07 pm 
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sjaustin wrote:
Interesting, thanks for the clarification, Keith.

If I understand correctly, this is due to the different electronic functions a pot can serve in an effects circuit. My method worked great when I used it on a tremolo pedal for toggling the rate control between a panel-mounted pot and an expression pedal. I assume that the rate control is wired as a variable resistor as opposed to a voltage divider?


You can always replace a pot in a 1-to-1 fashion. But it can sometimes be difficult, particularly with modulation effects as most "rate" pots are going to be reverse audio taper. So those can be difficult to find in a package that is suitable for mounting.

Most non-VCA LFO circuits' speeds are controlled by a capacitor charging and discharging and the rate pot acts as a variable resistance that inhibits that. And the resistance range usually needs to be within a specific range. The pot in an standard expression pedal is set up as a voltage divider. So it's nice when the parameter you want to control is based on voltage. Also, that value of the pot doesn't make a difference when it's being used as a voltage divide.

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Please do not PM me. email is prefered. keith@buildyourownclone.com


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