Add Expression Jack (Life Pedal)

[pokus]

Hey there,
anybody an idea how the expression jack on the V2 of the Life Pedal is connected?
Are all expression pedals universal by the way?

That's how the octave pot is wired in the Life Pedal. Just a simple blend control.

[11-90-an]

I can't find any schematic for the life v2 specifically, but here is a diagram on generally any expression pedal...




It seems like all expression pedals are similar, with different values for the current limiting resistor and the pot

[pokus]

yeah me neither. So a expression pedal requires an active part inside the other pedal to work? I thought maybe it's used to shunt one path (octave or clean) to ground or to change the octave pots ratio or whatever. So that just the exp pots resistance is used to blend clean and octave.

[MikeA]

Here's an in-depth explanation of expression pedals by Mission Engineering, with only minimal promotion of their own products.  https://missionengineering.com/understanding-expression-pedals/    There are several different configurations for expression pedals explained in the article.  For example, I have a Moog expression pedal that works with Strymon products but I had to make an adapter to use it with an ADA Flanger. Mike

[ElectricDruid]

So a expression pedal requires an active part inside the other pedal to work?

No, not always. Although in the example given the expression pedal is used as a voltage divider to provide voltage to an ADC input, it doesn't have to be. Note that the "expression pedal" side of the diagram about is entirely passive, and you have connections to the three pins of the pot. So you can use that however you like, and plug it into whatever you like.

I thought maybe it's used to shunt one path (octave or clean) to ground or to change the octave pots ratio or whatever. So that just the exp pots resistance is used to blend clean and octave.

I'd have thought you'd be able to replace the Blend pot you posted earlier with an expression jack. Use a stereo/TRS jack with normalled contacts, and then you can use the internal control until you plug in the pedal, at which point the pedal takes over from the panel control.


Incidentally, one reason ADC inputs are useful for expression pedals are that there's no standard pot value for expression pedals, so using the pedal as a simple voltage divider avoids that problem. A second benefit is that the same ADC input can also be used as a CV input to accept signals from synths and other gear.

[pokus]

I'd have thought you'd be able to replace the Blend pot you posted earlier with an expression jack. Use a stereo/TRS jack with normalled contacts, and then you can use the internal control until you plug in the pedal, at which point the pedal takes over from the panel control.

Thought about that, too. But two concerns came to my mind: Isn't the exp pot then just in parallel with the octave one and would give me some weird control range with a lot of interacting?
And can the expression pedal really act like a blend pot? It seems like there's always ground directly connected to one of the pots contacts.

[bluebunny]

The expression pedal wouldn't be in parallel with the internal pot if you used a switched stereo jack like this:



The internal pot is wired to the terminals you can see on the nearer side.  The lugs on the other side go to the PCB.

[pokus]

Alright that would do the trick.
I also guess there's no real ground in an expression pedal, other than on the wiring layout, as it's a passive device.
So according to the linked article it then should be tip to wiper, CW to sleeve and CCW to ring, to fit most of the existing expression pedals. I will give it a try.
Thanks for all your help!