Expression Pedal - a new update

Hi again dear MOD users

Once again I am here reporting about the long awaited Expression Pedal, our longest-living soap opera.

For those not willing to read a long text here’s the short version:

Albeit slow, the process is moving forward.

Release candidate metallurgy samples are being shipped next Friday.

Plastic gears have been narrowed down to the optimum teeth size and tooling is happening. Samples are to be shipped still in April.

Firmware is already functional but still in beta.

And now the long version :wink:

Catching up from my previous update, I am glad to tell that I managed to move important steps.

The gear pair is selected. I tried multiple pairs, from modules ranging from 0.7mm to 2mm and finally settled with a 1.5mm module. From my tests this tooth size yielded the best compromise between:

  • Possible variations for in-between gears distance due to tolerance adjustments;
  • Minimum teeth count for the pinion
  • Angular displacement multiplication factor.

The expression pedal is, mechanically speaking, an angular displacement amplifier. Foot movements bigger than 25 degrees are highly un-ergonomic. Since potentiometers have excursions of 270 or more degrees, it is desirable to use as much of this excursion as possible. With the selected pair we’re getting about 160 degrees of potentiometer rotation, which I find to be very good. The old expression from 2014 had a 45 degrees rotation on the pot and one could feel the noise from the pot influencing the action.

Here are two images to help you visualise:

On the top, the selected gear pair. On the bottom, my initial attempt with the very small module.

When using gears, the smaller the teeth, the smoother the rotation, hence my initial choice of the small module. But we’re dealing with a multi body system and the points of error generation are many:

1 - The flap that holds the pot is bent and can bring dimensional variations

2 - The U shaped articulation can be slightly misplaced

3 - The bolt that binds the pedal to the articulation has a minimum clearance that is not zero

4 - The attachment of the gear to the pedal can (and very probably will) bring a bit of misplacement to the big gear.

From the four items mentioned above, item 4 is the most problematic and I tried multiple ways to minimise the errors.

After trying side bolts, top bolts and even press-fitting bosses, I settled for male treaded studs welded directly to the aluminum pedal.

One very cool aspect of this arrangement is that it enables different gear pairs to fit the system in a interchangeable manner. That said, I will publish 3D files for matching gear pairs and those willing to change the mechanical responsiveness of their pedals will be able to easily 3D print their custom parts and attach themselves. Who says hacking is just for coding and electronics? :wink:

Details apart, the Expression is coming out beautifully. The final footprint of the unit is really appealing and I believe we managed to reach a great size X ergonomic relation. I do not know about you guys, but mammoths like the Ernie Ball and the Fender, albeit super comfortable, are a pain to carry. It feels like having one of those big old style american cars. On the other hand, all of the "mini" options - DOD, MXR and Zoom - feel to small for my sized 43 feet…

Last but not least, the firmware.

@jesse is doing a great job in providing a useful layout for the display info and also the arrangement of possible controls. The picture on the right side shows a rough sketch of what it will look like.

To close this long report, I’d like to reassure to you all that this is coming to life. I know the wait has been long and I personally feel even a bit ashamed of it. But that is life and unfortunately we cannot control all the aspects of it.

The MOD Expression is a product on its own and I now believe a company could be created only to design and sell it.

We keep pushing to offer you all the best we can. That’s the way we have acted till now and that is the way we will always do. I cannot allow myself to settle for less.

In the next weeks I’ll try to give you guys a proper - and realistic - shipping date.

Let’s all step onto the future!



thankyou @gianfranco for all the details; i’m delighted that you guys continue to dig into the details in a comprehensive and forward-looking manner.

can’t wait! :stuck_out_tongue: actually, yes, i CAN wait, and am happy to do so! :sunny:


Glad to hear the update as well! Quick question: I tried to find any information on this through scanning through threads, but is there a way I could preorder this as well? I’ve followed what’s been going on since October of last year, but have now decided I’d love to be a Mod expression pedal owner as well, and didn’t know the best way to become one. Thanks in advance!

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Thanks for the update! I know the wait will be worth it.

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@gianfranco: Did you ever consider a sensor instead of a pot? - many years ago I built a wah-wah unit using a magnet / hall-effect sensor, I also currently use a pedal board from another amp manufacturer which has wah and volume pedals, both appear to use some kind of optical / shutter system. In addition to the mechanical issues with gears etc, this also removes problems associated with scratchy pots (the main reason I gave up using a vintage wah pedal).

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@gianfranco thanks a lot for the update.
Love the mechanical hack by the way !

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I did @mike-overtonedsp

But there are so many other concerns in this case, specially the change in behaviour in different environment conditions. The units I’ve ever tried all had some caveat and thus in the end I opted for a properly implemented “old school” method.


Hello @gianfranco,

thanks for caring and thinking about the best user experience possible.
A friend of mine uses a volume / wah pedal with such optical sensor. I don’t remember if the translucent strip in between the diode and the photo sensor had been coded binary or if it just let less light through from one strip end to the other.
We had to play in bright sunlight and the sensor just freaked out. Neither volume nor wah frequency changes were possible.

Thank you and God bless, Marius

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Thanks for the update and perseverance @gianfranco! It looks really great.

Sorry if this is covered elsewhere but I was one of the backers of the original kickstarter and had included the expression pedal in my order. I haven’t been keeping up, so I’m not sure if the original orders will be fulfilled with this run. Do you have any specific info on my situation?

Sure. The Kickstarter backers will be fulfilled with this first run :wink:

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I have an FCB-1010 that I am using to control the parameters of the MOD. I suffer from this technology, because I can not get the pedal to respond to the close values of 0, that is, when the optical film should be absolutely translucent. I’ve opened, cleaned, repositioned the sensors and nothing … of the two pedals, one gives me 18 as a minimum answer and the other 30! … I bought a Wah because it was the effect that suffered most with this loss of amplitude of response, I’m using now only as tremolo speed controls and delay feedback, which I do not use near the minimum values. Today I already have preference for good old (and easily replaceable) mechanical potentiometers.

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I have both an FCB-1010 and a Line 6 Floorboard (I’m actually not much of an effects junkie, so I tend to just use a Line 6 amp and the Floorboard - though I still have an affection for genuine valve amps… because… well you just have to - there’s something about them) - both have always worked without problems though I can see how there might be environmental issues with any sensors. I don’t think there is an ideal solution (I had more trouble with traditional pots, though if they’re being used as MIDI controllers you can probably smooth out the analogue noise in ways which are obviously not possible when they form part of the wah filter or the volume attenuator).

Good news! :wink:

I have a modded firmware on my fcb1010 but I thought there was a calibration routine in the stock firmware as well. Mine was pretty bad before I calibrated.

Really Good news @gianfranco !!!
Thank’s for give us the news, and for keep doing this outstanding “state of the art” in MOD products.
The competence and compromise with quality and great respect with us, consumers, musicians and friends, that make us support and believe in MOD.

hello, do you still use the fcb1010 to control the mod? How are you doing? I was a while unused and now with the new updates (I believe that’s why) fcb is not responding well. From what I understand of the problem it is only working to turn the effect on or off, not both functions, and the expression pedal is not fluid while in motion and is alternating the values of 0 and the midway value. (remembering that he never rated 0 before, which was a problem I had)

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I have not tried it for quite some time, sorry. If I do I will let you know.

Thanks, I haven’t opened a topic for the bug yet because I’m not sure if it’s a problem with updates or because I spent a long time without using the equipment, I’m investigating. My FCB 1010 has a modified chip that allows Stomp box mode, and has always worked very well …

got your bug too I think, when I’m connecting my fcb1010 (EurekaPROM) on mod’s midi in/out.
I tried connecting it with my Roland UM-ONE mk2 USB MIDI Interface and it worked better, dunno if it was my midi cable or a problem with the duo’s midi in/out. I still have big delay with the expression pedal tho.

I use Eureka Prom 3. Well, I think I’ll have to go back to the 1.3 version of Duo (which I remember worked) to get that. Does the MOD team know this problem? I confess that I was out for a while.