Strymon Tech Corner #2 – Build your own expression pedal

Posted by Terry

Recently, I ended up with a broken crybaby wah. I was already lucky enough to own a 70′s thomas organ crybaby which I love, so sacrificing this second newer crybaby for a project seemed like a fun idea. Since the crybaby chassis is extremely rugged and I like the action of the pedal, I set out to turn it into an expression pedal for my El Capistan. This article assumes that you have experience soldering and using basic tools like wire strippers, etc. Of course, always observe proper safety precautions and wear safety goggles while working on any type of electronics.

crybaby wah sitting on green felt
Here’s my wah on the workbench.
crybaby wah pedal with back cover removed
First, opening up this box couldn’t be easier. Just remove the 4 thumb screws from the back plate and remove the plate.
crybaby wah pedal with electronics removed
Then, unscrew the two jack nuts from the input and output jacks and also remove the single screw holding the PCB (printed circuit board) to the chassis. Unplug the cable connector, remove the PCB and set aside.
crybaby potentiometer and switch with wires desoldered
Connect your treadle pot to a standard 1/4″ TRS (tip/ring/sleeve) jack according to the schematic in tech corner #1. Desolder all wires from the pot and switch and set aside.
crybaby wah pedal with original electronics removed and re-wired as an expression pedal
The “sleeve” of the jack is ground, so first connect that to the pin of the post closest to the footswitch. Then, connect a 1k resistor to the wiper (center pin) of the pot. Connect the resistor to the “tip” of the jack. Lastly, connect the pin of the pot closest to the jack to the “ring.” You’ve got an expression pedal!

Watch the youtube video for a walkthrough of the build process and an El Capistan demonstration with our completed diy project:

Happy shredding,
-terry

*All product names used in this article are trademarks of their respective owners, which are in no way associated or affiliated with Strymon or Damage Control, LLC.

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57 Responses to “Strymon Tech Corner #2 – Build your own expression pedal”

  1. David says:

    Great Info!

    Thanks!

  2. Paul says:

    I own an el Capistan and LOVE it. I saw your “How to make an expression pedal out of a broken wah” and I was wondering if you’ve ever tried converting an old Sewing machine pedal into an expression pedal? I have very limited space on my board, and the sewing machine pedals are so much smaller than Wah enclosures. I have yet to find any schematics on how to go about converting a sewing machine pedal. Any ideas? Is it really just installing a 1/4 jack and changing out a pot for a 10k pot or so? Any help would be great. I love the El Cap and really want to be able to put an expression pedal on the board, I just don’t have room.
    Thanks so much guys… and I hope you can help.
    I look forward to hearing back from you.
    Paul

  3. Jeremy says:

    Great tutorial! On tech corner 1 you mention that the EV5 among others has a second pot on it to allow you to fine tune the range of sweep of the main pot. Could you show us know how to do add one of these extra pots to the above example?
    Any pointers would be much appreciated!
    Jeremy

  4. Thanks, Terry! Very inspiring. I have an El Capistan and had briefly used an Ernie Ball Jr. Volume Pedal as an Exp. pedal. The 250k pot made it almost unusable, so a quick trip to “The Shack” today yielded a 10k pot, a stereo jack and a 1k resistor.

    It only took about 2 hours to modify the EB and have it up and running with the El Cap… amazing fun!

    The pot mount on the EB was the trickiest part, since the threaded shaft on the 10k pot was too short to allow the nut to lock it in; I ended up counter-boring the alum block a little to accommodate it, drilled a hole for the TRS jack on the front left, and voila… a solid aluminum expression pedal providing tons of versatility for the delay. I prefer it controlling the Mix function, but who knows what tomorrow shall bring. Fun stuff!

    I really love the El Cap… even moreso, now.

    :)

  5. Terry says:

    Hi Everyone, thanks for all of the comments! This is really great.

    @Paul, It’s really just about getting the potentiometer to turn when you move your foot. The electrical setup is simple, but getting the pot to turn mechanically might be tricky.

    @Jeremy, this second minimum value pot would be set up as a series variable resistor in the connection to ground (the shield of the jack).

    @Derek, Nice work!

    Happy Shredding,
    -terry

  6. duke says:

    I have a broken line 6 ex-1 and I want to replace the 20k pot with the 100k pot from the crybaby and put it back in the wah incosure. Will this work?

  7. Terry says:

    That will work just fine if you follow the wiring instructions above. If the 20k isn’t damaged that will work fine as well, no need to steal the pot from the crybaby.

  8. Reinhard says:

    One question: I would like to use the on/off switch under the pedal to also control some effect (on/off), using the second (now empty) opening of the original wah.
    Could you give me some info on how to do this?

    I would like to use this modded pedal along with my MFC101 Pedal board (for the Axe-FX Ultra), which has some decent wahs on board, so I could mimic the switching behaviour of a Wah-pedal when stomping on it.

    Thanks,
    Reinhard

  9. Terry says:

    Hi Reinhard,

    It’s possible most likely, however I am not familiar with the MFC101 midi controller so I can’t give more specifics. The basic idea would be to wire the two switch poles from the unused wah switch to the second 1/4″ jack.

    Terry

  10. Reinhard says:

    Hi Terry!

    Thank you for your response!
    One question remains …. what is the 1K resistor for, that you mention in your video?

    Thanks,
    Reinhard

  11. Terry says:

    Hi Reinhard,
    The 1K simply serves as a current limiting resistor in case of a short.
    -terry

  12. Hi!!
    I was able to modify my old EX1..I put a pair of TRX female Jaks, a 50 k volumen pot and I leave the original 20 k pot…and it works fine controlling my Brigadier and El Capistan..both at the same time, no bugs,,works fine ..I hope there will be no future electric damage for my devices.

    Best!!!

  13. Asbjorn says:

    Hi Terry!

    First i’m gonna say, you guys make some amazing pedals – i’m so excited about the sounds i get from my bluesky.

    I was wondering where I should if I want to buy the components to build an expression pedal. I don’t think my local guitar store have these components. Do you have any recommendations?

  14. Pedro says:

    Hello Terry!

    I want to made a expression pedal for my line 6 m5…
    what i need? a mono or stereo jack? i read that the pot is 10K. and the 1k resistance?

    Thanx!

  15. Terry says:

    Line6 does their expression pedals differently than pretty much everyone else. You use a mono cable and a 10k pot to vary the resistance from tip to sleeve.

  16. craig says:

    so for the line6 style would you use the same trs input jack but use a mono cable? and the crybabies pot would have to be changed to the 10k pot or would the original pot work?? Thanks allot!! I have 2 extra crybabies and would rather not by the plastic one that said company makes…

  17. Robbie says:

    I am building an expression pedal for my boss bass synth. I am using an old volume pedal but he value is to high I believe (250k audio). I used a stereo jack and wired it according to you schematic and used a stereo cable to connect. Nothing. I then used a mono cable and actually got an effect but not like it should. I guess my question is what value and type of pot would be best and should I use a tsr cable or standard mono?

  18. Terry says:

    Hi Robbie, you would have to know what type of expression pedal input the bass synth is expecting. I’d consult the BOSS manual and see if it recommends a standard expression pedal with a TRS cable.

  19. Brian says:

    Terry, I have modified a Cry Baby Wah to an Expresion pedal per your instructions, and of course it works! However, the sweep on the pedal is extremely short, making it unusable in practical terms – it goes from min to max with a very slight touch to the pedal. Is there a way to change the sweep so it is longer using resistors, or do I simply need to replace the original 100K pot with a 10K pot? ALSO, If I replace the pot should it be a linear taper pot and is 10k the right value?

  20. Terry says:

    Hi Brian, you’ll want to replace it with a linear taper pot to get a more even sweep. 10k or 100k will work.

  21. [...] has made a great post about converting a Cry Baby to an expression pedal. I just wanted to [...]

  22. Mike says:

    Hi, nice blog and site! I have a question about the resistor. What kind of effect is it on the 1K? Is it important to choose the right one?

  23. Kris says:

    Hi Terry. Thanks for this article. Very informative. Would a 2k resistor do the trick instead of a 1k. I have a few 2k’s lying around. Also, would a univibe replacement pot do the trick for a 10k pot sweep? Like this one: http://picclick.com/NEW-Dunlop-Univibe-UV1FC-160615320911.html I can’t tell if it’s linear or not.
    Thanks again. Love your pedals.

  24. Terry says:

    A 2k would probably be fine. That 10k pot should work great as well :)

  25. Kris says:

    Thanks terry. I might as well buy some 1k resistors while I’m at it. Are the carbon film? And what wattage? Thanks for your help. This is gonna be fun.

  26. Milo says:

    I just used this to solder up an expression pedal. Thanks for the info, I greatly appreciate it!

  27. kevin says:

    So if I wanted to do this for to control my Line 6 DL4 what would be different from what you laid out above?

    Thanks.

  28. MarkFL says:

    I just took my crybaby, opened the back, and moved the pin connector over two places to the left (which bypasses the battery and who knows what else). After that, it actually works as an expression pedal. However, the pot makes it so that there is barely any sweep to it. However, this can be a pretty cool effect in itself with certain midi parameters so it is a free and totally reversible mod. Just thought I’d share.

  29. Van Faux says:

    Hi,

    I have a Line6 M13 and an under utilized Vox Wah. I’m wondering if these 2 combinations would work? Mono\Stereo?

    Please advise.

    Thanks \m/

  30. Sol says:

    I am trying to build the expression pedal from an old CB 535Q and I was only able to get a 3 conductor 1/4″ stereo phone jack. Will this work?

  31. Terry says:

    A 3 conductor 1/4″ jack is TRS (tip/ring/sleeve) and is exactly what you need :)

  32. Sol says:

    thanks Terry.

  33. Jacob says:

    So is a stereo cable required for this to work???????

  34. Terry says:

    Yes, a TRS stereo 1/4″ cable.

  35. Eric says:

    This is great! However, I’d really like to install another jack to control another pedal simultaneously. Is this possible?

  36. Terry says:

    If both pedals are Strymon pedals it should work. With other brands, all bets are off because the control voltage specification could be different.
    A caveat to this is that you’ll likely create a ground loop and possible noise between the pedals by ganging them together.

  37. Eric says:

    That makes sense. Thanks anyway!

  38. Anthony says:

    Can anyone walk me through how to do this with a crybaby 535 and a stereo guitar jack?
    The pot on mine looks different so I’m not sure where the wires go.
    Please email me at guitarest@aol.com if you can help. Thanks

  39. Gerard says:

    Wooow… speechless i was going to buy a line (cheap) 6 expression pedal for my m9 but now i think i´m going to just undust my old cry baby..3 questions though…1. do i need a new pot or the one in the cry baby will do the thick? 2. the resistance is necessary for this EP1-L6 clone and 3 . the jack on the cry baby is a regular, mono (TS) guitar cable…can i use that?? thanks terry your are indeed the man!! by the way i reckon They are wired Tip and Sleeve.

  40. Terry says:

    Hi Anthony, what does the pot look like? Not familiar with the innards of the 535 specifically.

  41. Terry says:

    Hi Gerard, the Line6 ep-1 is a non-standart expression pedal design. I believe it uses a 10k but I am not certain about that. I know that is does use a standard TS cable (not TRS) and simply varies the resistance of the pot between the tip and sleeve.

  42. Chris says:

    Thanks for the great article! I have an EV-5 around that needs the potentiometer replaced. Do you have any idea what the specs for that pot is? The pot that shipped in mine is made by Alpha and is stamped with “8h3″ (the 2nd pot that adjusts the range is stamped with “8h4″) but I haven’t managed to find any specs just yet.

    Are there any minimum / maximum specs that I should keep in mind or is a pot a pot and they simply vary by size? I believe the pots in the EV-5 or other wahs are described as rotory potentiometers. Is any difference between the form factor of such pots or are they all the same?

    Any suggestions for manufacturers of pots that are better quality than others?

    Thanks in advance for you help!

  43. I’m looking to convert an Ernie Ball volume pedal to be an EV-5 equivalent, so I ordered the EV-5 pot as a spare from Roland UK (current part number is 01678156). The pot has no obvious manufacturer mark and is labelled “10kΩB”. I’ve measured the resistance from “off”/-150° to “full on”/+150° in 10° increments; the pot reads <1Ω from -150° to -40° and 8.82kΩ from 60° to 150°, and from -30° to 50° the values are 1.01k, 2.11k, 3.07k, 3.98k, 4.97k, 5.95k, 6.84k, 7.90k, and 8.75k. So there you go – highly non-standard, flat at the sides and linear in the middle.

  44. Nadnet says:

    Hi Terry,

    What about the same except using two pedals simultaneously (same brand) in order to use the expression feature for both. A la Pigtronix Dual Expression Pedal
    We could reuse both jacks and the switch on the pedal.
    What is your point? Could you show us hte way to achieve this?
    Thanks in advance!

  45. nacho says:

    Hi! i have just done it, and have tried it with a digitech rp50 for the whammy effects. but instead of having the signal all dry at heel position and all wet at toe position, its only full wet in the middle and stays all dry in both heel and toe position. im using a stereo cable. what can i have done wrong?

    thanks

    -btw, i’ve used a stereo jack like this one: http://www.synthrotek.com/wp-content/uploads/2010/11/amp_stereojack_id.jpg
    does it matter?

  46. Ron says:

    Can’t wait to to convert my Boss FV-60 to a double CV pedal. One question- how do I know which pin on the pot is ground, just in case they aren’t labeled? I have a little knowledge of electronics and schematics. Once I know that I can do the rest.

  47. rick says:

    @Ron, if you watch the video, at the 3 minute mark, terry wires up the ground connection. On the pot, it’s the pin all the way to the left.

  48. Craig says:

    I would like to convert my soon to be faulty crybaby into an expression pedal for my line 6 M13. I know they use a mono jack instead of TRS jack. Can this be done in a similar way to your tutorial above but wire the jack socket differently to suit the M13. Thanks.

  49. Dylan says:

    There’s one thing i’m not understanding – did you use the original 100k pot in the video? Where would you get a 10k pot that would work in the crybaby, with the treads?

  50. Vasya says:

    Hello. I`ve made everything according to the instruction but got no effect with strymon timeline. I believe that the problem is in the pot. The value of it A100K (audio). Do i need to switch to 10kB or 100kB or even something else in order to make it work with timeline?

  51. rick says:

    @Vasya, a 100k pot should work just fine. You could try switching it out to be something like 25k to see if that makes a difference. Also, make sure you are using a TRS cable to connect the expression pedal to the TimeLine with and make sure the Global menu for the Expression Pedal input on TimeLine is set to PEDAL and not TAP.

  52. Anthony Kirckof says:

    Hi! I’m trying to mod my wah pedal into an expression pedal and it isn’t working; the pot works fine and my el cap works with other expression pedals fine; the only difference I had to work around was that my crybaby had a Hot Potz II instead of the Hot Potz I that the crybaby in your video had, but it wasn’t hard to find out which terminal was which. But when I plug my el cap into the expression pedal, it always reverts to the completely open position, no matter how I engage the wah pedal. The jack, resistor and pot all seem to be working perfectly fine; is there anything else that might not be working here?

  53. Lee says:

    Hey, Terry. I hope you don’t hate me for asking… but will this work alright with my Timefactor?

    (I’m sorry.)

    Thanks!

  54. Hugo says:

    This project pedal is designed to work with any pedal requiring a TRS expression pedal. The Timefactor web page states that the Expression input is a Mono input, which would not work, so you may want to check with Eventide to be sure.

  55. Reg says:

    Great mod! After watching the video I went straight out and picked up an old Broken Crybaby and did the mod, however it works backwards with my Timeline, ie: heel=toe and vise versa. I swapped the tip and ring wires around but it’s still doing the same. My way pot looks a little different, lugs are on the back. Any advise? What have I done wrong?

  56. Hugo says:

    @Reg – Instead of swapping the TIP and the RING, try swapping the TIP and SLEEVE instead from how you originally wired it up. If you still have trouble, please email support@strymon.net.

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